How to change Spark Plugs on a 2004 TB with 4.2l [Archive] - Chevy TrailBlazer, TrailBlazer SS and GMC Envoy Forum

: How to change Spark Plugs on a 2004 TB with 4.2l


keitho64
05-03-2007, 02:41 PM
Hello

I wrote a HOW-TO on changing spark plugs. I took pictures while I did this as well. It looks like I cannot upload the pictures or Word Document until I post more. I tend not to post much as I find everything using 'Search'. So here is the text of the article I wrote. If anyone wants the actual word document with pictures send me a PM with your email address.


************************************************** *
So you want to change your spark plugs in your Trailblazer/Envoy with the 4.2L 6? I have a 2004 Trailblazer EXT 4X4 with the 4.2L 6 and did this a while ago. This is a very simple job that took me about 2 hours because I decided to snap some pictures. I will outline the steps I went through. I make no warranties regarding these instructions, I am merely offering up my notes as to how I did it. The tools needed are a straight blade screwdriver, 5/8 Spark Plug socket, 10mm and 13mm sockets, extensions and ratchet, anti-seize and new plugs.

The first step is to remove the Air Resonator and intake tube. There are two hose clamps, one on each side of the resonator that you remove. There are held on with clamps that use a straight blade screw driver. Once the hose clamps are removed you need to pull the hose off the resonator that goes to the air filter. Next there are two 13mm bolts on the passenger side that hold the resonator to the valve cover. Remove these. Next lift up the resonator from the passenger side and then pull the resonator off the throttle body. Store this, the clamps and bolts for reassembly.

Now you will have ready access to the coil packs and plugs. Each coil pack is held on with a 10mm bolt. I did one at a time to make life easy. Unscrew the 10mm bolt from the coil pack. I took a small straight blade screwdriver and pried up on the coil pack. Once the pack is loose I pulled it up and set it to the side. There is enough wiring that you can easily do this. Next use a 5/8 spark plug wrench and remove the plug. Use care that nothing falls into the spark plug hole. I put a little anti-seize on each of the plugs so removal will not be so hard next time. I gently tightened them down. If you prefer to use a torque wrench you would need to look up the specs.


Here is a shot of the coil pack pulled out of the way to gain access to the plug.


Here is my finished product, topped off with a K&N Cold Air intake. When I did this I ended up installing Bosch Platinum +4 plugs. The only reason is that is all I could find. I would have preferred Nippon Denso Iridiumís but they were not available. After the new plugs and K&N (My TB had 45,000 miles when I did this) I took a trip to Florida. I had a cargo topper on, 3 kids and my wife and I. I averaged 75MPH the entire trip and 19.5MPG. This is a marked improvement from where I started. Around the city it is averaging 15. While not stellar mileage, it is better. As for power it is really hard to say. I tow a 4,800lb RV trailer with the TB and the first trip is coming up soon. I am anxious to see if this helps. I was contemplating trying a TB spacer from Air-Raid as this is supposed to help low speed performance. I am very skeptical of things like that but if I can find one on eBay cheap enough I may just try.

If there is enough interest in this article I also did brakes on all 4 wheels. I may write that up as well. Thanks and hope this helps someone out.

I the moderator wants the Word document shoot me a pm and let me know how to post it.

Keith

crazytb
05-03-2007, 04:07 PM
good post..but don't bother with the tb spacer..majority say it is not worth the money...also when do you recommend changing the sparkplugs..i have an 04 with 30k but i bought it used

Super 88
05-03-2007, 04:30 PM
good post..but don't bother with the tb spacer..majority say it is not worth the money...also when do you recommend changing the sparkplugs..i have an 04 with 30k but i bought it used

:iagree:
The owners manual of my 05 states to replace the plugs at 100K. I have heard of others of this forum who have done so at that mileage.
FWIW many have had problems with the Bosch Platinum +4 plugs on these engines. The OEM Delcos are the recommended ones when it's time to replace them.

http://forums.trailvoy.com/showthread.php?t=21855

rbarrios
05-03-2007, 04:40 PM
u can wait till 100,000 if its operating properly.

I changed mine at 100,000.
I noticed no performance difference. no 'significant' difference. I mean it worked fine before.
the used ones looked used of course, but didnt look to be in terrible shape. I changed simply because they reached 100K.
I did use the new Iridium tipped AC delcos
if you dont feel comfy, maybe 75K?

scover5555
05-03-2007, 07:54 PM
I was thinking I read somewhere not to use anti-seize on the spark plugs

lfb57
05-03-2007, 10:54 PM
I have heard horror stories about plugs seizing or galling in aluminum heads. I always use a small amount of never-seize on threads of replacement plugs - especially if they're likely to stay in place for 50,000+ miles. I am careful not to put so much never-seize on that it might foul the (gap).

rmac694203
05-04-2007, 03:30 AM
Yeah, I have heard the opposite. I was told to always use a bit of antiseize on the threads of sparkplugs. Especially with aluminum heads. I do with my Lincoln, which I change the plugs on about once a year (probably unnecessary but I use copper plugs and its easy as hell to do). Are the heads on TB's aluminum BTW?

scover5555
05-04-2007, 11:08 PM
I stand corrected, it was a different engine I was thinking of :duh:

t02owner
09-26-2007, 01:47 AM
I have the same question about anti-seize on the plugs.
I have always heard/believed that with aluminum heads it is a good idea to use it, however the local dealer service dude told me "GM does not recommend using it".

I replaced my plugs @ 100k and there was not any evidence that it was used originally but of course it might have cooked off long ago.

So still a dilemma ... to seize or anti-seize?

BTW the old plugs were in surprisingly good shape and I could not tell a difference in performance after the change + throttle body cleaning.

I am very interested in the truth/facts about the anti-seize. I worry that I may have created a future problem by not using it.

Thanks

bullethole
09-26-2007, 09:14 AM
Re: the 10mm bolts that hold down the covers over the spark plug hole. Make sure the engine is cold before removing these bolts. Some have had them break off in the head while trying to remove them from a warm or hot engine. They are fairly long and thin, so it does not take much to wring them off.:nono:

Bearcat
09-26-2007, 09:17 AM
Re: the 10mm bolts that hold down the covers over the spark plug hole. Make sure the engine is cold before removing these bolts. Some have had them break off in the head while trying to remove them from a warm or hot engine. They are fairly long and thin, so it does not take much to wring them off.:nono:
:iagree:Spark plug change is recommended at 100,000 miles, but you may want to do so earlier to avoid breaking the hold down bolts. Definiely use anti-sieze when you replace them. Steer clear of the Bosch's, nothing but trouble.

rbarrios
09-26-2007, 04:27 PM
i think I emailed AC delco on this...... and the reply was not to use it.

carp
09-27-2007, 12:32 PM
I would use the anti-sieze on the 10mm bolts holding the coil packs down.

LOWRIT00
09-27-2007, 03:54 PM
I did it! I took my stock plugs out at about 50k. check them and put anti-seize on the threads and put them back in, just cause I read about guys breaking them off and have thread damage after pulling them out at 100k or so, any time you can prevent something costly why not do it.
key is not to put so much that its going to cause a problem, just enough to make your job easier when that time comes.

everyone does what they want to there trucks, just cause GM cause to do or not something doesnt mean its going to hurt anything.

Impalacat
09-27-2007, 04:24 PM
I haven't changed my plugs on the T.B. yet, but on my 00 truck I changed them at 68,000 because on some truck sites they where talking about getting them out of the head was a problem, when I pulled the plugs they had anti-seize on the original plugs from the factory, so I used a dab of anti-seize on the new iradium plugs also.:cool:

keitho64
04-23-2008, 01:56 AM
Now that I have enough posts to publish the pictures here you go.

I have a few comments as well, I installed the Bosch Platinum +4's. They seem to work OK but personally I do not like them. I am going to swap them with a set of Nippondenso irdium plugs. I know the manual says change them every 100K but my problem is I plan to keep this vehicle a long time. I do not want to have to worry about removing the plugs from the aluminum head after that long. I guess you can call it cheap insurance.

Keith

rbarrios
04-23-2008, 01:19 PM
thanks. this should help others on here.
I changed my plugs at 100,000.
I used a breaker bar to easily turn the plugs....
where they stuck? I dont know.
I didnt want to be leaning over the engine trying to loosen the plugs with a normal sized ratchet.... so I used a breaker bar and just easily turned the plugs. they came right out. I didnt see any signs of them being seized or anything.

gixxer_751
05-09-2008, 05:51 PM
ha, just what i was looking for.. seems im good for another 40k miles:bonk:

Wake
05-14-2008, 01:15 AM
...I installed the Bosch Platinum +4's. They seem to work OK but personally I do not like them. I am going to swap them with a set of Nippondenso irdium plugs.

What is it that you don't like about the Bosch plugs??? I have tens of thousands of miles in several vehicles with them and never had a problem... In fact, I'm currently in the middle of a cross country road trip and posting from a hotel room in Santa Rosa, NM... I filled up just inside of NM and 65 miles into the tank I'm showing 24.5 mpg average economy with my 3.73 geared 4x4, 67 mph and A/C on the nearly flat lands of I40...

Now I know the plugs aren't gaining me anything mileage wise, but they certainly ain't hurting performance...

rsnow46
05-14-2008, 10:30 AM
On my '06 I changed the plugs at 53K, and replaced with the 41-103's. I could tell right away a small improvement in pep - seat of the pants. Mileage on a 300 mile trip was up .5 mpg. The only trouble I encountered was the plug socket has a rubber insert to hold the plug, and my socket was old, so when I replace the next to last plug (naturally) the rubber insert stayed with the plug, and I didn't see it. I felt a resistance with I tried to connect the coil wire, so I felt around in the hole and determined what happened. I used anti-seize (as always) and the dielectric grease inside the plug wire. Thanks to everyone on the pictures, info and the change in the AC plug number. I definitely suggest changing them before 100,000.

jonathank2000
07-17-2008, 02:15 PM
This is great info! I plan to run Seafoam and change plugs this weekend... my first time. Is there a DIY thread or site with pictures? .. don't want to screw anything up.. thanks!:)

rbarrios
07-17-2008, 02:20 PM
just remember... change them on a cold engine.

jonathank2000
07-17-2008, 02:30 PM
Good to know. I have 182,000 miles on my 2003 Envoy. I got the plugs changed about 90,000 miles ago so they are due. I also got the plug wires changed at that time too (dealer recommended). Should I change the wires also just to play it safe?

02NYenvoy
07-17-2008, 03:28 PM
Our trucks don't use wires. Check back with your dealer.

rbarrios
07-17-2008, 03:47 PM
you have a receipt that shows that the plug wires where changed???:confused:

mrbflat
08-30-2008, 06:11 PM
:thumbsup:

Just replaced my plugs yesterday. Used AC Delco 41-103s. No anti-seize.
Took about 2 hours, only because I took my time and also cleaned the throttle body at the same time. I was a little worried about that #6 plug way in the back, but it was easy!! Also, had to fight to get that #1 coil pack out, but I eventually worked it out.

Thanks for the post. It was right on point and made the job alot easier.

Smerker
08-30-2008, 10:05 PM
Check this out. I did a google search for 2003 GMC Envoy Plug Wires and found the following.

http://www2.partstrain.com/store/?Ntt=Spark%20Plug%20Wire&N=1623%2010505+4294967262

They also have plug wires for the 2004 then for 2005 they show nothing...

I have to go look. I have a 2003 but I have only had to open the hood to check the fluid levels. I have only had it a couple years now.

markarock
08-31-2008, 12:53 AM
just remember... change them on a cold engine.

Consider a slightly different take on this advice. My advice is to remove them on a hot engine. But don't install them until the engine is totally cold.

Here's my logic. The coefficients of linear expansion are not the same for steel and aluminum. They are:

Steel 11.0 to ~13.0, depending on the composition

Aluminum 23.0

http://en.wikipedia.org/wiki/Coefficient_of_thermal_expansion

As you can see, for a given increase in temperature, aluminum expands about twice as much as steel. So, if the engine is hot, the aluminum will have expanded more than the steel spark plug, so it should come out easier.

For installation, however, if you put a cold steel plug into a hot aluminum engine, you will be able to screw it in further than if the engine were cold. Then, when that hot engine cools, it will really contract tightly around the threads of the plug and make it almost impossible to extract.

I suspect that the quoted advice comes from the fact that my explanation and advice are too complicated. So the advice is simplified to "don't change plugs on a hot engine that has an aluminum cylinder head" (or even an iron one for that matter, though the problem doing so will cause is much less severe). Whichis the advice that is normally given.

To me this analysis and advice means that if you have a problem plug that you are having a difficult time extracting from an aluminum head, get the motor up to operating temperature and try again. I think you will be surprised. But don't ever put a steel plug in a hot engine, but if you must, torque it very lightly!!!

On another note, I seem to recall from my Corvair days that the advice against the use of Never-Seeze or the like was due to the insulating properties of some formulas. You need to have a good ground from the plug to the head, and some compounds act as a barrier to the flow of the current. That said, I have never had a problem with an engine from using it, so the issue may be more theoretical than real. However, when I removed a plug in my '03, I reinstalled it "dry". It came out easy enough, so I wasn't afraid that it would seize in the hole. I have removed plugs in other motors at 100k and never had a problem so it seemed to me that the advice against use of anti-seizing compounds is legitimate.

Yes, I know:

1. There's always a first time
2. Better safe than sorry
3. Experience keeps a hard school, but a fool will learn in no other.
4. Etc.

But that's what I did. I weighed the advice against using it, considered the sources of that advice, and then considered that I haven't had any problems yet, and decided to stick with the factory and plug manufacturer recommendation.

Mark

Super 88
08-31-2008, 01:03 AM
I'm not for a second going to dispute your logic, because frankly I'm just not that smart and don't know enough about it.

But I'm curious - does anyone know what they usually do at the dealerships? I'm not saying that the dealerships are the know all/end all for this type of thing, just wondering what the common custom is!

reedtchsrv
08-31-2008, 04:33 PM
Just did my plugs. Piece of cake. Don't let the back one scare you. With the right length socket extension, there is plenty of room. Pulled and cleaned my throttle body in the process. Again, piece of cake. I spent most of my time arguing with the little grey connector locks on all of the electrical connectors.

Great write-up on the throttle body:
http://forums.trailvoy.com/showthread.php?t=43912

hec123
08-31-2008, 04:36 PM
New to forum,40 plus years experience with anti-seize.

I am a Locomotive Diesel Mechanic/Machinist by trade.
When I started work for the railroad in 1968 as an apprentice Machinist,anti-seize was a everyday word.At that time it was not available on the open market,it was used and sold for industry only.

Every mechanic had a can/w brush of anti-seize in his tool box.It was used on any threaded surface that would be in a heat affected environment on the external components of the loco engine.

I could give HUNDREDS of examples and applications as to how the use of anti-seize has saved me many hours of work in the last 40+ years,however I won't bore you with that,I will get to the subject of anti-seize use on spark plugs in aluminum heads or in any application where there is two different metals in contact with each other.

Metals have their own characters,they do not expand and contract at the same rate when subject to heat,be it hot or even warm.

Aluminum expands and contacts at a faster rate than steel.
If the engine (the 4.2L6) head is hot or even moderately warm it will be cooler and there for smaller than the steel spark plug. At the same time the steel spark plug will be larger,because it looses its heat at a slower rate than the aluminum head.Do you see what is going on here?Big spark plug threads+small spark threads in the aluminum head=a tight spark plug (steel)being backed out of a aluminum head.
The threads are softer in the head and will be damaged.

The same applies to the 10mm bolts that hold the COP(coil on plug)in place on the head.

Remove the plugs from a cold engine only and use anti-seize sparingly on the plug threads and you will be fine.

HEC123:thumbsup:

WOOLUF1952
08-31-2008, 04:59 PM
Just did my plugs. Piece of cake. Don't let the back one scare you. With the right length socket extension, there is plenty of room. Pulled and cleaned my throttle body in the process. Again, piece of cake. I spent most of my time arguing with the little grey connector locks on all of the electrical connectors.

Great write-up on the throttle body:
http://forums.trailvoy.com/showthread.php?t=43912

IMO It is much easier to leave the wires attached. Just move the coil off to the side. DO NOT let the coil hang from the wire.:m2:

reedtchsrv
08-31-2008, 05:09 PM
I looked up the price of the COPs and I wanted them resting safely on my workbench. I'm 100% Polish. If it's within arms reach of me, I will probably do something stupid to make the project more costly than going to the garage in the first place.

WOOLUF1952
08-31-2008, 05:14 PM
I understand and feel your pain.:tiphat

jrgroundhog
09-24-2008, 04:57 PM
I just changed my plugs this morning. Decided to do it myself after the dealer quoted me $200. I used Bosch Platinum 4+ and after just one lap around the block am extremely pleased with the noticable power difference. While I've changed plugs on many vehicles previously, never one with the COP layout. It was pretty straightforward, although if I can add my own bit of advice it would be to try to loosen the wiring housing in front of the number one plug. I had much more trouble with number one than six. If it is not loosened properly, as I almost found out, the housing has the potential to crack. I won't really affect anything if it does, as the wiring itself has another shield, but no one wants to look at cracked plastic. One other piece of advice is to have as many different lengths of extensions for your socket wrench as you can find. I cycled through four or five combinations for efficiency and trying to save my knuckles from abuse.

Bearcat
09-24-2008, 05:03 PM
I would avoid the Bosch plugs altogether. A lot of folks here have found problems in their Voy's.

rbarrios
09-24-2008, 05:26 PM
two freacking hundred....!!!!:suicide:

I did mine at 101,000. But I didnt know dealer wants that much....

slimfast
09-24-2008, 05:45 PM
Bosch plugs, ouch, you will drive around for 2 weeks and then......you will ask why does my car kind of sputter, or jitter, or misfire.....well it's the plugs. When I put in the bosch's it was great for a couple of weeks and then on the highway I notices a little slight sputter. It felt like when a big gust of wind hitting the car about every 6 seconds. I thought it might be the fuel filter, but then I remembered that it never happened before I pt the new plugs in. Long story short I went to the E3's and it's drives like new. let us know how those new E3's work in a month.:bonk::bonk::bonk::bonk::bonk:

jrgroundhog
09-25-2008, 08:14 PM
Yeah the dealer(s) in my area bundle a couple of fluid checks and other things that are a piece of cake. And, of course, the labor is the most expensive part of the deal. I'll look out for the sputtering but the Bosch is what they were going to put in anyway, only the 2+ instead of the 4+.

gmac310
10-01-2008, 04:22 PM
I guess I'm lucky (although talking about it now probably jinxed me!) but Ive had Bosch +4's for about a month now and, knock on wood :duh:, haven't had any probs.

Envoyevolution1
10-02-2008, 06:23 AM
Hey Guys, Tony here..Just wanted to say thanks for all of the really good advice, Keith your pics got me through it, and it was pretty easy....Also cleaned the tb as well....And if you guys are ever in charlotte, drop by.:grouphug:

Jim 951
10-21-2008, 06:43 PM
I just serviced my '02 TB. I am in France, where this vehicle is pretty rare, so I really appreciate the help I've found here.

I replaced my spark plugs with Denso Iridiums. I noticed that the 6th spark plug (windshield side) was full of oil... All other were dry. Is this alarming?

I also replaced air and oil filters and cleaned the throttle body, but didn't have enough time left for the gas filter. I still have to replace my windshield wipers motor (I already have the parts), and the TB will be like new.

By the way, it is running either on LPG or gas.

rbarrios
10-22-2008, 01:06 PM
being an 02--- I wouldnt worry about oil in the plug hole.
after time oil has seeped thru...
now if it was an 08 with 5000 miles and lots of oil.. then Id worry...
When I changed my plugs at 101,000 I found oil in a few of my plug holes.

E34M30
12-28-2008, 03:26 AM
Yeah, I have heard the opposite. I was told to always use a bit of antiseize on the threads of sparkplugs. Especially with aluminum heads. I do with my Lincoln, which I change the plugs on about once a year (probably unnecessary but I use copper plugs and its easy as hell to do). Are the heads on TB's aluminum BTW?

Yes, the 4.2L has an aluminum head. As well as the 5.3 I believe. The 4.2 is a lost foam cast aluminum block also, ever wondered why if you take a close look at your block, it resembles styrofoam? Cause thats what it started out as:)

E34M30
12-28-2008, 03:31 AM
Does anyone have any previous experience with their 4.2 misfiring? I just replaced the spark plugs at 100k, and it ran perfectly until I replaced the plugs. Of course I put in the spendy bosch, and it ran like crap, so I replaced them with the stock ACDelco units, and it ran fine for a month or so and started misfiring again. Each time I read the code it changed which cylinder was misfiring, telling me it was pretty random. I replaced the valve cover gasket, as it has those seals between the head and spark plug/coil pack valleys. Still misfires... Any ideas?

wardak33
12-28-2008, 03:48 AM
might be a bad set of spark plugs or not gapped correctly. what type of plugs were they (platinum, double platinum, iridiums..etc)?

E34M30
12-28-2008, 02:17 PM
I've gone through three sets of plugs and all have given me the same problems. They have varied from the bosch double platinums, to ACDelco, and really cheap champions. All of them were properly gapped. I've gotten some hints that it may be because of moisture creaping into the coil pack valleys, and I've seen a repair article suggesting to replace the seal under the hood to prevent moisture from getting anywhere near them. I was just curious if anyone has replaced their AIP seal (i think thats what the article called it) when they were experiencing random misfires and if they had any success with it.

markarock
12-29-2008, 01:05 AM
I had to replace the seal on my 03 Envoy I6. I had a miss. Water had leaked past the old seal, ran along the top of the cam cover, and seeped into the plug hole under the coil pack. I put a code reader on it and it said that one cylinder was missing. I forget which one. I pulled the coil pack off, and looked down in the hole. Over an inch of water.

I wicked it out with some paper towels, then removed and dried the plug, and reinstalled it. Put some silicone grease around the porcelain of the plug, and on the coil pack seal before reinstalling the coil pack.

Shortly after that I replaced the cowl seal, having read that in hard rains and with the truck at a certain angle, water can get past the old seal and cause the problem I experienced. Once I installed the new seal, I never had another problem.

One thought on your symptoms, if you have the same problems with three different sets of plugs, then you are pretty much guaranteed that it isn't the plugs.

I don't think a tiny bit of moisture getting into a plug hole will cause a problem. Mine water level was high enough that it covered the bottom of the coil pack and got inside, allowing the plug to short. If you use silicone grease on your plugs before you install them, then even if your plug well is full of water, it shouldn't short out. IMHO.

Sorry, but I don't have any glimmer of an idea why you might be experiencing random missing. That's pretty strange.

keitho64
12-29-2008, 01:09 PM
E34M30 - Since you have changed all the plugs multiple times I would say it is safe to rule them out. Have you used an OBDII scanner to verify the miss fire is multiple cylinders? If so then I would think you can rule out the coil packs as well. I would consider the crank position sensor next as that may be the culprit.

Here is where my knowledge is a little fuzzy on the Trailblazer and maybe someone else can chime in. I see the TB with the 4.2 has both a Crank sensor and a Cam Sensor. I assume the crank sensor is for spark and the cam sensor is for the variable valve timing but I am not sure on that topic.

Let us know what you find out.

E34M30
12-30-2008, 02:25 AM
Yeah, sounds like I should look into that AIP seal. I did use an OBDII scanner to observe the misfire on different cylinders. I also replaced my cam position sensor. I think you're right about the cam/crank position sensors. I'll look into that further. Thanks for the help guys:)

roncbowen
01-13-2009, 12:29 AM
So I am new to this forum and really like it. I followed all of the advice I recieved about changing the plugs and cleaning the TB. Put it all back together and something is really wrong.
The truck has no power and seems to be "missing".

I called GM and they want $200 just to read the codes.

Any advice out there?

Thasnks everybody

petevw
01-13-2009, 12:42 AM
So I am new to this forum and really like it. I followed all of the advice I recieved about changing the plugs and cleaning the TB. Put it all back together and something is really wrong.
The truck has no power and seems to be "missing".

I called GM and they want $200 just to read the codes.

Any advice out there?

Thasnks everybody

Are you sure you put everything back correctly, and all the plugs are connected? Did you have the battery disconnected while doing the plugs & TB?

Don't go to the dealer to read the codes....try a local AutoZone, or NAPA.....they usually will check the codes for free (thinking their going to get a sale out of it).

Also, are you sure you put the coil packs back into the spark plug well straight? If not, the little spring at the end may not be touching the top of the spark plug. Are the coil pack electrical plugs all the way back on each coil?....those two things will make a BIG miss.

roncbowen
01-13-2009, 01:01 AM
Thanks for your response.

I was very careful to put everything back as it went out.

However frankly I never really looked at the coil packs. I just pulled them out and carefully laid them on the side and changed the plugs and put them back in.
If they are seated correctly I thought they would automatically be straight. And I have no idea what you mean about "a little spring". Again I never looked up into the black plastic thing surrounding the part of the coil pack that goes in the engine.
Could you eleborate more?

Thanks again

02NYenvoy
01-13-2009, 10:43 AM
I think you should remove each coil and re-seat them. It takes just one to not fit onto the sparkplug for misfire, it's common.

jrgroundhog
01-13-2009, 12:14 PM
If they were just sitting off to the side they could have gotten some dirt or debris on the connection. There is a bright side, though. Now that you've done it once, taking it apart again should be fairly easy.

rbarrios
01-13-2009, 02:05 PM
also--- did you disconnect the battery?
It may be that your throttle body is dirty and now operating badly.. expecially if youre running the AC to defrost etc...causing the engine RPMs to drop etc...
Did you disconnect battery?

roncbowen
01-14-2009, 01:54 AM
Thanks everyone:

Yes the battery was disconected the whole time I worked on this. Somehow I purchased a battery that is not sealed and what a pain it is to take of the battery case to inspect the fluid level.
I guess I will have to take everything off and inspect and reinstall it first. I am concerned about the spark plug gap. I used the AC delco platinum -103's. Everything I have read says they do not need to be gapped. However there is a note on the box saying to gap them.
I am new to this site and really like it. Thanks again everybody.

Blazernut
01-14-2009, 05:54 AM
Thanks everyone:

Yes the battery was disconected the whole time I worked on this. Somehow I purchased a battery that is not sealed and what a pain it is to take of the battery case to inspect the fluid level.
I guess I will have to take everything off and inspect and reinstall it first. I am concerned about the spark plug gap. I used the AC delco platinum -103's. Everything I have read says they do not need to be gapped. However there is a note on the box saying to gap them.
I am new to this site and really like it. Thanks again everybody.

Just in case someone stumbles across this and thinks about gapping the new plugs ....

The spark plugs on these have a new number and are now iridium. The iridium plugs should not be gapped because of the surface coating. If it is compromised by scratches they can fail prematurely. If I did not see damage to the box or the spacer over the tip I would do a delicate check on the gap without force but nothing major that may cause disruption.

I see you got Platinum plugs which is strange as I thought they had been discontinued ages ago? :undecided I am unsure if the Plats are a fussy about their surface being compromised as the iridiums.

roncbowen
01-15-2009, 02:37 AM
Thanks BIll,

THey are iridium, my mistake.

I got lazy and took it to the shop today. I had taken it to Chevy yesturday and they wanted $180 just to read the codes. I found a Napa place that quoted me $95 to read the codes.
I took it in and they found one coil not seated properly, and just charged me $95 out the door.
THey all felt seated when I put them in and seemed to snug down square, anyway I still saved a bit over the $200 the dealer wanted to change them and I cleaned the throtttle body while I was in there.

Thanks again

Menthol
04-07-2009, 01:43 PM
Thanks BIll,

THey are iridium, my mistake.

I got lazy and took it to the shop today. I had taken it to Chevy yesturday and they wanted $180 just to read the codes. I found a Napa place that quoted me $95 to read the codes.
I took it in and they found one coil not seated properly, and just charged me $95 out the door.
THey all felt seated when I put them in and seemed to snug down square, anyway I still saved a bit over the $200 the dealer wanted to change them and I cleaned the throtttle body while I was in there.

Thanks again

Was it the #1 not seated properly and can someone please explaing how to take those d#*n plugs off the coil packs.

ben5491
04-25-2009, 10:20 AM
Thanks for all the info. I changed the plugs in my GMC truck at 104,000 and they were still working fine. I have 98,000 on the TB and I think with the info in this thread I will be ready to tackle the job today. Wish me luck! I am installing the AC/Delco original equipment plugs and no anti seize.:thx:thx

ben5491
05-25-2009, 10:44 AM
Done with that job, thanks for the help.:thx

ddddavidcccc
06-03-2009, 08:26 PM
I read a lot of posts concerning replacing the plugs in Envoy/Trailblazers and it is easier than it appears.

Front plastic chamber comes off easily as described with two bolts left side, one hose under, one hose on right corner near grill, and two clamps.

Not necessary to remove the wiring. Coil can be put on the side of the motor on something clean.

Front plug is hard to get to due to the plastic box containing wiring, but the single bolt on the top of the coil assembly can be removed with a wrench rather than a socket.

Blow out the debris in the spark plug chamber then remove the plug. New one seats to the right torque almost automatically. Used a torque wrench, but the plug only went in to the appropriate torque anyway.

Use the old plug to push in an pull out of the coil assembly to get a feel of what should happen when it is seated properly. Then as you put each coil in place, make sure that you pull it up after it is seated to make sure that the coil was properly seated, then push it down again and bolt it.

Repeat the process and it should be done in a short time. Hardest one was the first plug due to the plastic box. Used Iridium plugs as GM recommends them as the replacement. So far so good with those.

rbarrios
06-04-2009, 12:47 PM
Thanks BIll,

THey are iridium, my mistake.

I got lazy and took it to the shop today. I had taken it to Chevy yesturday and they wanted $180 just to read the codes. I found a Napa place that quoted me $95 to read the codes.
I took it in and they found one coil not seated properly, and just charged me $95 out the door.
THey all felt seated when I put them in and seemed to snug down square, anyway I still saved a bit over the $200 the dealer wanted to change them and I cleaned the throtttle body while I was in there.

Thanks again

Dealer wanted $180 to read the damn code?
NAPA wanted $95?

those are A HOLES!!!

Im a little surprissed NAPA read your codes.
In CA- the new law is that no parts store can read your codes. They cant loan the scanner either.
Auto Zone was popular for the employees coming out to read your code.
You could also go and rent the tool.
But withing the last year- the law is you cant rent the code reader- and the employees cant come out and scan your code.
So you have to have a shop or dealer do it.
The other option is to buy your own code reader--- the auto parts sell them...
the simple ones can be something like $40. But im sure they usually range about $100.
Ebay I think has some $40 ones that simply read the code.
But at the $95 price you could have bought a code reader that read and erased the codes.

Super 88
06-04-2009, 01:12 PM
Dealer wanted $180 to read the damn code?
NAPA wanted $95?

those are A HOLES!!!



Why do you say that? Yes it's cheaper to go buy your own reader, but some people wouldn't have any idea of what to hook it into, much less what the readings mean.

I would agree that 180 seems a little high, but you are paying for a service. I'd bet a lot of places would waive at least part of that fee if you have the vehicle serviced there.

Think of going out for a good steak dinner. Sure you can buy a decent steak for 5 or 6 bucks and cook it at home, or you can go out and pay 20 bucks and up for about the same thing.

arcsound
06-07-2009, 02:35 AM
What is the purpose of this law? Whatever perceived "protection" justified this BS, it can't be worth the lost benefit of giving car owners an alternative to dealers and service stations for helping diagnose fault codes. Figures CA (or New Jersey...) would come up with more regulations to "make our lives better"! Unbelievable.

Sprinter2x
06-24-2009, 06:43 PM
Great post and photos.

Has anyone swapped the plugs at 95k miles? I'm wondering how much the old ones are going to resist benig removed. I know a cold engine is a must. (I used to do this all the time with Japanese motor cycles but they were never anywhere near 100k mark.) The dealer wants $200 and acts like they're afraid of it.

keitho64
06-24-2009, 07:09 PM
Great post and photos.

Has anyone swapped the plugs at 95k miles? I'm wondering how much the old ones are going to resist benig removed. I know a cold engine is a must. (I used to do this all the time with Japanese motor cycles but they were never anywhere near 100k mark.) The dealer wants $200 and acts like they're afraid of it.


Glad to hear this helps. The main reason I changed mine early was due to fear of them being stuck. My other car has 65,000 miles and I plan to do them soon as well. It is more involved as the intake manifold must come off. UGH who engineers these things.

Anyway if you have 95K I think you will be ok. As you pointed out start with a cold engine and have patience. You may be surprised that they come out OK. Let us know how it goes.

rbarrios
06-24-2009, 08:02 PM
Great post and photos.

Has anyone swapped the plugs at 95k miles? I'm wondering how much the old ones are going to resist benig removed. I know a cold engine is a must. (I used to do this all the time with Japanese motor cycles but they were never anywhere near 100k mark.) The dealer wants $200 and acts like they're afraid of it.

I changed mine at about 101,000.
They came out fairly easily.


as for the $180--- I thought the dealer would charge maybe $25-$50...

California is special....
just today- I was driving by a local city street..
I saw some sings that said- prepare to stop... Survey ahead..
Highway patrolman in 1 lane- orange cones and all...
the lane had a special setup with computers and techs and a canopy---
they had a Trailblazer on rollers..... with wheels turning-- and a fan blowing the radiator---
I think they were randomly picking cars and testing for emissions by having vehicle roll on rollers (real world conditions)....
Or surveying as the sign said...

ToddMeister
06-25-2009, 04:04 PM
I just did my 02 TB at 96K, engine was cold, was pretty easy job overall. Old plugs came out just fine. Put in the AC iridiums. Also cleaned throttle body while it was apart. Runs great! Idle is better now.


Great post and photos.

Has anyone swapped the plugs at 95k miles? I'm wondering how much the old ones are going to resist benig removed. I know a cold engine is a must. (I used to do this all the time with Japanese motor cycles but they were never anywhere near 100k mark.) The dealer wants $200 and acts like they're afraid of it.

78Southwind
09-30-2009, 05:15 PM
Thanks for the write up.

notnodak
09-30-2009, 07:31 PM
I just did my 02 TB at 96K, engine was cold, was pretty easy job overall. Old plugs came out just fine. Put in the AC iridiums. Also cleaned throttle body while it was apart. Runs great! Idle is better now.


Just did mine and they came out real nice. Mine was at 120,000 miles. took out the originals and replaced with Iridiums. Very noiticable difference, it needed it.

rrufast
09-30-2009, 08:06 PM
Glad I stumbled on this thread... I need to swap mine out on the TB. It has just over 100k on it now.. so it's time.

Guess I could clean the Throttle Body up again also... By reading, it appears that the AC-Delco plugs (103's) have been replaced by Iridiums.. IS THIS CORRECT?

Probably will do a step by step pictorial for this as well.. haven't noticed one here yet....

ddddavidcccc
10-05-2009, 11:57 AM
Yes, the AC-Delco plugs (103's) have been replaced by Iridiums. I checked at the dealer to see if I could get get the old ones, but they are discontinued. I was concerned about going to a different type of plug, but have had no problems and did notice a slight increase in power and gas mileage over the platinums in the Envoy. Just one note. Do not pull off the spark plug wire from the coil. They are nasty to get back on. Only work with the plug end.

Process is pretty straightforward once you get started. Best to start on the second plug in first as that does not have plastic brackets in the way. Once that is done, then do the first one when you have the feel for it.

Riddlebox0333
11-28-2009, 05:07 PM
Thanks, Info helped alot, just changed mine today.

Knielson
11-30-2009, 03:08 PM
Excellent post, I just changed my plugs also but @210,000km I installed a airaid intake and a T/B Spacer. My milage has increased from 22 imperial miles per gallon to 24.5 last fill. I can not say what the difference was with the throttle body extender as I did all this work at once but for the 100 dollars I can not say I lost anything as itwas very easy to install as I had it all apart to do my plugs and intake. I feel I do have better throttle response intake or spacer who knows but I does sound deeper.I have alot of km's on my rig but it runs like it is still new. My only issue is that I have a whinning sound (like an alternator) but it does not seem to be weak and I have had it for some time, like since I bought it do you have any thoughts I will be posting this to the public also but it seams like you have a good bit of knowledge on the T/B.
Thanks Kyle:thumbsup:

Chickenhawk
11-30-2009, 06:10 PM
My only issue is that I have a whinning sound (like an alternator) but it does not seem to be weak and I have had it for some time, like since I bought it do you have any thoughts
Change the idler pulley. It's not even a half-beer job and it will be shockingly quiet.

There are lots of other pulleys and bearings that can cause this, but most of them will also lead to a decrease in performance. The idler pulley is by far the most common to replace and is the likeliest suspect.

Even if it isn't, if it has never needed replacing, it will soon anyway.

Gary 5354
01-10-2010, 07:50 PM
Great Site Guys,

Doing the plugs later this week, among other items, 2002 6cyl with 136K miles.
One question, what is the torque spec for the plugs? I understand the cold change due to the alum block, and never sieze application.

Thanks & I will be back with the codes after more searches.

Gary

izzyduzit
01-10-2010, 08:23 PM
I just did mine last week. It's 156 in. lbs. or 13 ft. lbs. Same thing. Double check, it should be written on the top of the engine when you take off the air resonator. To the left of the coil packs.

Gary 5354
01-11-2010, 06:33 AM
Izzy,
I am used to working on diesels and nearly everything has a torque spec.

Thanks again,

03 BlazerEXT
01-11-2010, 09:41 PM
I too haven't had the need to change spark plugs in a whiole with two Dodge Cummins sitting in the driveway. The TB is a bit over 140K so I would say its just a bit overdue.

JRad
01-16-2010, 05:31 PM
Just changed my plugs today. I'm a little confused on the Delco numbers being tossed around on here. My parts guy sold me AC Delco 41-103 which are labeled as Iridium plugs. My owners manual called for 41-981's which I assume are the discontinued Platinum plugs. I compared the new to the old before installing and they looked identical, so I put them in. The truck runs fine.

One oddity when removing the old plugs, some of them had lots of oil on the threads. We looked in the wells before before removing the plugs, and the wells were clean. The old plugs were not oil fouled and the oil was only below the shoulder, not above on the hex or porcelain. At first I suspected a leaky valve cover gasket, but this oil is on the threads only where the plug would be inside the head.

My truck does not burn, or consume oil. It has just under 100K miles.

Should I worry about this?

Chickenhawk
01-16-2010, 05:54 PM
Nope.

You did just fine. Those are the correct plugs.

Enjoy your ride!

fj4072
03-08-2010, 02:45 PM
Just performed this change over the weekend. Pretty simple even though this was the first time I had done it myself on my TB with 170K+ on it. 25K miles ago, I found a shop that changed my plugs for $95, which was dirt cheap, considering all other shops wanted $250-$300 and all of them acted like they were afraid of it. My TB wasn't idling correctly, which is the reason I just changed them again so early. I bought AC Delco 41-103. Pulled the first plug off, and found Autolight Platinums in there. I thought I would of found Bosch's in there since I've had many problems with those, but no problems ever with Autolight Plats with other vehicles. BUT I guess these engines just flat out run better with the 103's. This engine, with a clean throttle body and 103's, is one happy engine. WOW what a difference! I can't even tell it's idling. All hail Trailvoy.com:hail:

rcurley1
08-11-2010, 07:58 PM
Great directions. Thanks, save a ton by using this site.

flexeril
09-17-2010, 11:42 PM
Now that I have enough posts to publish the pictures here you go.

I have a few comments as well, I installed the Bosch Platinum +4's. They seem to work OK but personally I do not like them. I am going to swap them with a set of Nippondenso irdium plugs. I know the manual says change them every 100K but my problem is I plan to keep this vehicle a long time. I do not want to have to worry about removing the plugs from the aluminum head after that long. I guess you can call it cheap insurance.

Keith

Thanks for sharing these pics bro. Will be doing mine this weekend @ around 80k miles.

:thumbsup:

flexeril
09-18-2010, 12:12 AM
Dealer wanted $180 to read the damn code?
NAPA wanted $95?

those are A HOLES!!!

Im a little surprissed NAPA read your codes.
In CA- the new law is that no parts store can read your codes. They cant loan the scanner either.
Auto Zone was popular for the employees coming out to read your code.
You could also go and rent the tool.
But withing the last year- the law is you cant rent the code reader- and the employees cant come out and scan your code.
So you have to have a shop or dealer do it.
The other option is to buy your own code reader--- the auto parts sell them...
the simple ones can be something like $40. But im sure they usually range about $100.
Ebay I think has some $40 ones that simply read the code.
But at the $95 price you could have bought a code reader that read and erased the codes.


That is one F7879king stupid/dumb law! What purpose does it do? Only in Kalifornia.:hissy::hissy::hissy::weird::weird:

flexeril
09-18-2010, 12:16 AM
I changed mine at about 101,000.
They came out fairly easily.


as for the $180--- I thought the dealer would charge maybe $25-$50...

California is special....
just today- I was driving by a local city street..
I saw some sings that said- prepare to stop... Survey ahead..
Highway patrolman in 1 lane- orange cones and all...
the lane had a special setup with computers and techs and a canopy---
they had a Trailblazer on rollers..... with wheels turning-- and a fan blowing the radiator---
I think they were randomly picking cars and testing for emissions by having vehicle roll on rollers (real world conditions)....
Or surveying as the sign said...

Were these jackaces reimbursing the gas spent while the vehicle was on the rollers? I would have refused.

steevesj
05-04-2011, 08:35 AM
For those thinking about waiting till 100,000 to change plugs I would not wait. I just did mine at 60,000 and most were very worn (there wasn't must left of the center electrode). The old plugs were the AC Delco 41-981. I replaced them with the 41-103.

Hog
05-06-2011, 10:45 AM
That is one F7879king stupid/dumb law! What purpose does it do? Only in Kalifornia.:hissy::hissy::hissy::weird::weird:That is kinda weird. I do see frequently where, a person will get a code read, then they start throwing parts at the vehicle in order to fix the problem. Buit I owuld think that the parts store wouldnt mind this at all, as they would sell more parts.

A code reader is agreat tool, but is only 1 small part of diagnosing issues. I got my simple code reader for $100 IIRC from Canadian Tire. You can buy them at any automotive store. Some not only read codes, some even read back some realtime sensor data.

Change plugs only on a cold engine with aluminum head(s). The older 2.2 and 2.4l engines had messages in teh engine bay and under the coil pack cover that read" change plugs on cold engine only". 1 service book went so far to say to let vehicle rest for 24 hours before removing plugs.

The biggest pronblem with aluminum heads, and spark plugs in general is that guys over torque the plugs in the 1st place. Torque specs are VERY important, esp. these days with very tight tolerances, and money saving techniques.

I have noticed thecenter pucks on the ground strap come off way before the 100,000 mile mark. Just because you can run them til 100,000miles, doesnt mean you should.

peace
Hog

rrufast
05-25-2011, 10:29 PM
I finally changed my plugs today. Much overdue @ 125k, but that's another matter.

I used a 3" extension, a 10" extension and two 3/8 swivels to get to all the plugs. Like someone else noted, the rubber sleeve insert on my sprak plug socket stuck to three of the six plugs. I used long needle nose pliers to grab the boot off the plug.

The one thing I noticed is that while the coil packs really were snugged down and "popped" off I couldn't' noticeably tell that they "popped" back into place. I was worried that once I snugged them down that something would wind up amiss when I tried to crank the truck. As a measure of caution, I cranked the truck prior to putting the intake resonator back on the throttle body and it seemed fine. I buttoned everything up, installed the resonator, my air kit and then cranked the truck up and let it idle while I wiped off the tools and put them back up.

Came out, took my dog for a ride and no issues whatsoever.

Between this and the new 02 sensor I installed yesterday (to cure the P0103 code) there are no codes (at this time) and it does seem to have a slight more oomph to it.

The ting I noticed that also troubled me was that plugs 2 and 5 were literally dripping wet with oil. DRIPPING WET. The others were all dry. They were wet from the threads down, so I can't even imagine how these were able to fire at all if they were actually submerged in all that oil... I guess the valve seals must be really bad on those two cylinders? Wondering if this is something I should be overly worried about?

04TBEXTowner
06-20-2011, 01:56 AM
I absolutely refuse to pay $6 a plug for any vehicle. I've had great success with NGK G-Power iridiums ($3.29 ea.) on multiple vehicles, anyone opposed to them on the '04 TB with 75k miles on it?

the roadie
06-20-2011, 11:02 AM
I absolutely refuse to pay $6 a plug for any vehicle. Your frugality is noted. Your engine may run like crap without 41-103's and then you've paid twice. Do you also refuse to change your oil until your $11.99 Jiffy-lube coupon comes in the holiday mail? :dielaugh:

$40 for plugs over 75K miles is not a real hardship, is it? You could remove the crossbars from your roof rack and get enough fuel economy gain to save $40 over the next 75K miles. Ahhhhh, but the roof rack savings are distributed and relatively invisible, and the spark plugs are an instant sticker shock. I understand. Carry on. :coffee

Bearcat
06-20-2011, 02:02 PM
Your frugality is noted. Your engine may run like crap without 41-103's and then you've paid twice. Do you also refuse to change your oil until your $11.99 Jiffy-lube coupon comes in the holiday mail? :dielaugh:

$40 for plugs over 75K miles is not a real hardship, is it? You could remove the crossbars from your roof rack and get enough fuel economy gain to save $40 over the next 75K miles. Ahhhhh, but the roof rack savings are distributed and relatively invisible, and the spark plugs are an instant sticker shock. I understand. Carry on. :coffee
Well said, sir! :tiphat

rockstardann
06-20-2011, 02:17 PM
:iagree:

drives2much
06-20-2011, 02:49 PM
Roadie,

You're a tough act to follow!!!:D I changed mine this weekend and it wasn't as bad as I thought it would be in terms of both time and effort. Thanks to the write up, it was a pretty straightforward process.

the roadie
06-20-2011, 02:57 PM
From my favorite brewing co:

04TBEXTowner
06-21-2011, 12:51 AM
Your frugality is noted. Your engine may run like crap without 41-103's and then you've paid twice. Do you also refuse to change your oil until your $11.99 Jiffy-lube coupon comes in the holiday mail? :dielaugh:

$40 for plugs over 75K miles is not a real hardship, is it? You could remove the crossbars from your roof rack and get enough fuel economy gain to save $40 over the next 75K miles. Ahhhhh, but the roof rack savings are distributed and relatively invisible, and the spark plugs are an instant sticker shock. I understand. Carry on. :coffee

A simple yes or no would have done. Thank you.

T78brian
06-24-2011, 02:09 PM
When I called the local Chevy dealer to question about a tune up deal they had(to find out the deal had ran out, of course), I asked what the service included and what it cost to have it done now. I was quoted $600 to replace the plugs and boots. I promptly told them, NO thank you, I'll do it myself .

the roadie
06-24-2011, 02:28 PM
...I was quoted $600 to replace the plugs and boots. I promptly told them, NO thank you, I'll do it myself .You could have said, for $600, I could hire Angelina Jolie to change them and have more fun watching.

Are they NUTS?!?!?!?!?! :confused:

fj4072
06-24-2011, 02:38 PM
You could have said, for $600, I could hire Angelina Jolie to change them and have more fun watching.

Are they NUTS?!?!?!?!?! :confused:


Amen there brother! But to be politically correct, you should of said Angelina Jolie OR Brad Pitt. :laugh:

martyelzz3
06-28-2011, 08:26 PM
I changed my sparkplugs on my 4.2 this weekend. What a PITA for a SFOF like myself. All was fine until the last plug, way the heck in the back. I took a break... read some similar stories on here and dove in... well crawled across the engine and got'er done. The old plugs were...OLD at 114K I think they were the original plugs. Replaced with AC Iridims.. (where's the spell checker when you need it?) If I still have it at 200K I think I will show my grandson how to change them.:crazy:

xxomegawpnxx
07-05-2011, 01:39 AM
Thanks to all of you guys I did this job in an hour. Im the guy that you could say "you need to change the kerflapper valve" to and would completely believe you. Didn't have an issue with anything really, used the ACDelco 41-103 Iridiums with no Anti-Sieze, used some dielectric grease as well. I found the front one to be the "hardest" even though it wasn't bad just had someone hold the black wire casing up while I removed the coil. Little tip for anyone going to do it, remove the throttle body. It takes 2 seconds and saves 2 hours. BTW my local shop quoted me $70 which doesn't include the plugs. They were closed so I did it myself :)

WOOLUF1952
07-05-2011, 02:31 AM
Thanks to all of you guys I did this job in an hour. Im the guy that you could say "you need to change the kerflapper valve" to and would completely believe you. Didn't have an issue with anything really, used the ACDelco 41-103 Iridiums with no Anti-Sieze, used some dielectric grease as well. I found the front one to be the "hardest" even though it wasn't bad just had someone hold the black wire casing up while I removed the coil. Little tip for anyone going to do it, remove the throttle body. It takes 2 seconds and saves 2 hours. BTW my local shop quoted me $70 which doesn't include the plugs. They were closed so I did it myself :)

So, did you have any trouble finding a name brand kerflapper valve? :D

Also, did you clean the throttle body while you had it off?

xxomegawpnxx
07-05-2011, 02:59 AM
I actually had cleaned it on 6-2-11 so no, although I wish I had done the plugs while I had it off then.