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



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  #1  
Old 05-03-2007, 01:41 PM
keitho64's Avatar
keitho64 keitho64 is offline
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2004 Chevy TrailBlazer LT EXT
Graphite Metallic 4.2L I6 4X4
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How to change Spark Plugs on a 2004 TB with 4.2l

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
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  #2  
Old 05-03-2007, 03:07 PM
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crazytb crazytb is offline
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2004 Chevy TrailBlazer LS
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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
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  #3  
Old 05-03-2007, 03:30 PM
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Super 88 Super 88 is offline
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Quote:
Originally Posted by crazytb View Post
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

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
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  #4  
Old 05-03-2007, 03:40 PM
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rbarrios rbarrios is offline
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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?
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  #5  
Old 05-03-2007, 06:54 PM
scover5555 scover5555 is offline
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2003 Chevy TrailBlazer LS
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I was thinking I read somewhere not to use anti-seize on the spark plugs
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  #6  
Old 05-03-2007, 09:54 PM
lfb57 lfb57 is offline
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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).
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  #7  
Old 05-04-2007, 02:30 AM
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rmac694203 rmac694203 is offline
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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?
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  #8  
Old 05-04-2007, 10:08 PM
scover5555 scover5555 is offline
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I stand corrected, it was a different engine I was thinking of
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  #9  
Old 09-26-2007, 12:47 AM
t02owner t02owner is offline
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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
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  #10  
Old 09-26-2007, 08:14 AM
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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.
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