5.3L Cylinder 7 Misfire [Archive] - Chevy TrailBlazer, TrailBlazer SS and GMC Envoy Forum

: 5.3L Cylinder 7 Misfire


mi5htymike
09-16-2010, 01:24 PM
Hey guys. Let me start off by saying I'm new here and also new at servicing(or trying to service) my own vehicle. Therefor, I apologize in advance for being informationally challenged when it comes to cars. Anyhow, I'm having issues with my 06 Envoy. The vehicle has 85,000 miles. The check engine light came on and it was running extremely rough. I had it scanned, and it came back as a cylinder 7 misfire. I changed the plug and wire on 7 which didn't solve the problem. I then swapped coil 7 with coil 5, to see if the misfire would follow the coil. I rescanned it, and it's still reading a misfire at 7.
How should I proceed? A friend suggested fuel injector cleaner. However, I'm afraid to drive it as the check engine light intermittently flashes while driving, so I fear damaging the cat. Is that a legitimate concern, or can I run the injector cleaner through? Should I just proceed to replace the injector? Thanks in advance.

markarock
09-17-2010, 07:41 AM
Injectors do go bad, but not that often. I had one go bad at about that mileage. So it could easily be your problem.

I doubt that cleaner will work since the motor is missing and not simply running rough at idle--which would be more likely with a partially clogged injector. Though it is the cheapest attempted fix, my prediction is that it would be a waste of money.

One test you might want to do before replacing the injector is a compression test on that cylinder, just to rule out some more expensive problem. If the compression is OK, I'd just replace the injector, clear the code, and take it down the highway with crossed fingers.

Mark

mi5htymike
09-17-2010, 10:28 AM
Thanks Mark. I'm going to proceed with the injector.

mi5htymike
09-18-2010, 05:18 PM
Update. Took it to the shop. Compression test shows no compression in cylinder 7. So far they found two collapsed lifters. Lots of $$$$$$$. 85,000k and maintained well this definitely shouldn't be happening. Very frustrating.

markarock
09-18-2010, 08:18 PM
Update. Took it to the shop. Compression test shows no compression in cylinder 7. So far they found two collapsed lifters. Lots of $$$$$$$. 85,000k and maintained well this definitely shouldn't be happening. Very frustrating.


Hope you didn't replace the injector. Looks like yer gonna need the $. Sorry to hear the bad news. :worried:

You are correct, that shouldn't happen at that mileage, and it seems pretty suspicious that you have TWO collapesed lifters. One I could understand, but not two. There is something else going on. Also, my experience is that lifters don't just collapse, but they do get noisy and "tick". So you might want to verify that it is a lifter problem.

It may be a camshaft problem, not a lifter problem. You may have wiped the lobes off the cam. That's been known to happen. Happened to me in another car, but it was only one lobe, not two. You need to do a thorough search for the cause, most definitely.

You might want to have your oil analyzed. Be interesting to see what they can tell you. Might give a clue as to the cause.

mi5htymike
09-18-2010, 11:29 PM
Thanks Mark and good advice.

No I didn't replace the injector, and like you said, good thing because I will need all the money I can get for this one.

I took it to the GMC dealership today for a second opinion, so I'll hear from them on Monday. The shop I had it at said they found two collapsed lifters, but also said he would have to search for further issues/causes. At that point I told him to just put it back together as the estimate he gave me for the best case scenario was something I couldn't afford. After thinking about it I decided to bite the bullet and use the credit card, so that's when I decided to take it to the dealership.

I wonder if contacting GM might be of any value? I'm guessing since I bought it used with 35k on it they'll just tell me tough luck.

markarock
09-20-2010, 07:33 AM
I bought mine with 49k from a dealer--it will be two years ago in December--and it came with the 5 year/100k powertrain warranty. The kind of problem that you are having would be covered.

If you don't have the warranty, you can ask, but don't get your hopes up. Keep us informed.

mi5htymike
09-20-2010, 12:58 PM
GM dealership confirms two collapsed lifters. Their explanation for a cause: "Dirty oil". When I explained to them that I've maintained the vehicle well and get the oil changed religiously, they point the finger to the original owner not changing the oil regularly. I got the vehicle at 35k, and have had it for 50k, so I doubt that's the issue. I'm pretty sure there would have been some warning signs had that been the cause. Pretty lame explanation for the cause of problem if you ask me.

Anyhow, they quoted me $3800 to replace all the lifters. I wonder how much a new engine would be? I'll have to look into that.

markarock
09-20-2010, 08:58 PM
That's an outrageous price, IMHO, and a BS explanation. Even if they never changed oil before you bought it, a highly unlikely situation, that didn't cause the problem. It went 50k after that. Their "explanation" is BS and "convenient". There's an explanation for what happened, but theirs certainly isn't it.

I'd really like to see the results of an oil analysis if it still has the same oil in it as when the problem began.

I'd start looking at some boneyards for a complete motor. You can find I6 motors for around $500, but don't know what a 5.3 would be. But it is a very common engine, so you should be able to find one easily, even if it is out of a Tahoe or another model. Even if it was $1000, and the labor to install it, you would be way better off than $3800.

My suspicion is that it has something to do with the DOD lifter mechanism on that cylinder. That would be my guess at this point, but poor maintenance by the former owner is highly unlikely. You can pull a Carmax report and possibly find the previous owner and ask him/her. I would.

I can't see parts and labor for replacing two lifters costing anywhere near that much. They need to remove the intake for sure. Don't know if they must remove the cylinder head, but even if they do, that is way too much money, again, IMHO. Maybe they are figuring a new cam and new lifters. Even so, too much $$.

I'd be curious what some engine-knowledgeable 5.3L owners have to say.

mi5htymike
09-21-2010, 01:55 PM
Do you send your oil out somewhere or do you have somewhere local to take your oil for analysis?

markarock
09-21-2010, 09:18 PM
I use Blackstone Labs. They will send you a free collection and return packaging kit.

I'd get the full analysis this time, which includes the amount of anti-wear additive left in the oil.

Check out this thread for a link to their site and a comparison of Mobil 1 and Amsoil.

http://forums.trailvoy.com/showthread.php?t=50104&highlight=blackstone

mi5htymike
09-23-2010, 12:52 AM
[QUOTE=markarock;999921]I use Blackstone Labs. They will send you a free collection and return packaging kit.

I'd get the full analysis this time, which includes the amount of anti-wear additive left in the oil.

Check out this thread for a link to their site and a comparison of Mobil 1 and Amsoil.

http://forums.trailvoy.com/showthread.php?t=50104&highlight=blackstone[/QUOTE

Sounds good. Very interesting. I'm now considering just selling the Denali when I get it back from the shop. If I decide to keep it I will definitely get the oil analysis. I'm pretty interested to see an oil analysis on my 94 z28. I also wonder what the results would have shown with the Wix Filter and M1 oil?

Lee614
09-23-2010, 08:28 PM
I would go back and inform them that "dirty" oil didn't cause this problem. and the previous owner was located and they did their oil changes on as suggested by GM's DIL.
So ask for the district service warranty manager.

Record the conversation on your cellphone for future possible use. This engine should be covered and if they don't cover it.. tell them there will be hell to pay. (I assume you have the 100k warranty.)

mi5htymike
09-27-2010, 03:15 PM
I'm pretty sure the vehicle had a 3yr/36k mile warranty. Is the 100k warranty you speak of an extended warranty?

RedRocketZ28
09-27-2010, 07:07 PM
Damn, $3800 to replace lifters on a 5.3? I will do it for $500, haha. Granted you have to pull the intake and the head on that side, but that is outrageous.

Was the motor making any audible noises or did it just have the misfire? Usually a collapsed lifter makes the engine tap quite loudly. If the oiling system was not up to par or there was gunk that got into the lifter it would make it not be able to pump up. Hopefully it didn't do any further damage like drop pieces into the oil pan and get passed through the motor. Hope nothing else is damaged in there.

I have seen stranger things happend but collapsed lifters on a stock motor are not very common at all. On a side note, my buddy is selling a used 5.3 with 60k on it for $500.

mi5htymike
09-29-2010, 01:47 AM
Damn, $3800 to replace lifters on a 5.3? I will do it for $500, haha. Granted you have to pull the intake and the head on that side, but that is outrageous.

Was the motor making any audible noises or did it just have the misfire? Usually a collapsed lifter makes the engine tap quite loudly. If the oiling system was not up to par or there was gunk that got into the lifter it would make it not be able to pump up. Hopefully it didn't do any further damage like drop pieces into the oil pan and get passed through the motor. Hope nothing else is damaged in there.

I have seen stranger things happend but collapsed lifters on a stock motor are not very common at all. On a side note, my buddy is selling a used 5.3 with 60k on it for $500.

Yes the noise was as you described. Got the work done for $1500, not bad compared to the $3800, but obviously much more than the $500. Eh well...

greeneagle
01-01-2011, 09:10 PM
gentlemen,

I have a 2005 GMC Envoy SLT XL with the 5.3L, I'm looking at replacing my second set of so called collasped lifters...one year ago, I had the lifters replaced on cylinder #6 at 105K miles and now I'm looking at replacing the lifters on cylinder #4 at 136K miles...why didnt the dealership replace all the interior four cylinders I dont know...it my understanding that the four interior cylinders are different than the outer cylinders... the cost last year was $2500 and now it going to cost at least $4500 and a new motor cost $5200 without labor.....so I'm being to believe that GM has a problem with these lifters. I beginning to believe these lifters are a for runners of their fuel management system.....

mi5htymike
01-04-2011, 12:18 PM
gentlemen,

I have a 2005 GMC Envoy SLT XL with the 5.3L, I'm looking at replacing my second set of so called collasped lifters...one year ago, I had the lifters replaced on cylinder #6 at 105K miles and now I'm looking at replacing the lifters on cylinder #4 at 136K miles...why didnt the dealership replace all the interior four cylinders I dont know...it my understanding that the four interior cylinders are different than the outer cylinders... the cost last year was $2500 and now it going to cost at least $4500 and a new motor cost $5200 without labor.....so I'm being to believe that GM has a problem with these lifters. I beginning to believe these lifters are a for runners of their fuel management system.....

The more people I talk to the more common this problem seems to be. The one shop I was at says it's a very common problem with this motor.

joshbaker626
01-04-2011, 12:33 PM
I have had very similar issues with my 05' TB 4.2 engine. I had a dead cylinder 5 and was told it was going to cost a fortune. I fount a ton of used motors in town between $800-$1200. However, I had a mechanic buddy start looking and he found out it was a broken valve spring. Cheap part but takes quite of labor time. Still a lot cheaper than a new motor.

mtpihlblad
01-11-2011, 11:41 PM
I had a misfire today on cylinder 7 in my Saab 9-7x with 75k miles today, after reading this thread I am very worried. I will troubleshoot this weekend, but need to confirm that cylinder 7 is on the driver's side closest to the firewall. Mike, did you contact GM about the failure, how did that go?

Thanks,
Matt

mtpihlblad
01-13-2011, 03:15 PM
Please disregard my previous post, long story short a lifter is bad at 73k miles. I am thankful mine is a 2007 and has the 5yr/100k mile powertrain warranty. The dealer says that they will replace all 16 lifters so I guess it will be good until at least 150k miles.

MP

milworker
04-24-2013, 09:34 PM
I know, I don't own a Trailblazer or Envoy, I own a Yukon XL SLT 4x4. BUT I had the same problem with my 5.3L, though MUCH more noticeable. One of the lifters in cylinder #1 collapsed and basically sounded like a bag of quarters rattling around in the engine. $5000 later and I had a brand new engine complete with warranty. What is truly screwed up though is this is COMMONPLACE. It seems a lot of folks are having this issue regardless of how well you maintain the engine. Some call it soft camshaft, which would explain why some don't report the jackhammer / bag o' quarters sound, while other get the racket. GM said it is not a known issue, that it's improper maintenance, whatever. I NEVER had a collapsed lifter in the old SBC 350s. It ran, or it didn't. Any thoughts on this? How many folks have dished out good cash for this problem?

Scooter1963
04-09-2014, 03:03 PM
Looks like I've officially joined the Cylinder 7 misfire club.
At around 100,000 it was cylinder 1 misfiring at idle and check engine light on. #1 plug was fouled so replaced the plug. All good til about 120,000 when it did the same thing. Replaced the plug again but only got 3000 this time (123,000). My friend owns a garage & he advised me to take it to GM Dealer which I did. They claimed I had clogged ports in the valve cover and put on a new valve cover and did the intake injector super duper cleaner process (actually the second time injector cleaner was done as my buddy tried this at 120,000). Picked it up, left the GM Dealer and with-in 10 miles check engine light came back on - turned around - they claimed that the coil packs were wet from detailing the motor and they dried them out - went on my way again and after about 15 miles noticed rough idle so I turned around again - they claimed same thing but promised to fix and provide a loaner it if it ever happens again.
Now 2 months later and at 126,000 it began to idle rough again and check engine light came on so I took it back to GM Dealer and was informed that cylinder 7 has misfire and plug was fouled and replaced the plug (oh, and added some oil additive) - feel like I've been here before.

Covert Olds
04-11-2014, 01:18 PM
Thought these LS engines were supposed to be so great??? I'll be doing a cam/lifter swap in mine to get rid of the DOD crap if l have an issue like this. Or maybe l'll sell it. Not a big fan of the vehicle after owing it for about 8 weeks now anyhow.