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2003 gmc envoy_slt
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10 Posts
try swapping a coil from another nearby cylinder and see if the misfire stays with that cylinder or moves with that coil. If it moves its probably just a coil but if it stays you could be looking at possible engine related problems
 

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2006 chevy trailblazer_ls
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113 Posts
I have the same issure for just over a week now, and today on the way to work my engine light went off!, So should i just monitor it for a few days and see if it comes back on? I did order a new coil pack, but i guess my best bet is to hold off putting it in?
 

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2002 chevy trailblazer_ltz
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18 Posts
P0303

I'm having the EXACT same problem only in #3 cylinder.

One mechanic replaced the plug and the error code didn't change. He couldn't help me much further, and the mechanic they recommended said they couldn't really work on it unless it was actually occurring, and since the problem is intermittent it's literally hit or miss...

The engine sputters, the service engine soon light is steady unless I go above 2000 rpm, then it blinks. When I cruise or idle, it goes back to steady. If the engine "corrects itself" the SES light stays on for a few more miles but eventually goes away.

The first mechanic said it might be the fuel injector, but I don't think it would act this way if it were the injector.

It started about 2-3 weeks ago, and is very intermittent. I'm out of ideas, but I don't want to wait until I've blown something to get this fixed.

02 Trailblazer btw
 

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2006 chevy trailblazer_ls
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113 Posts
I have a coil pack from a 04 i just bought but doesnt fit my 06. If anyone is interested, its 24 bucks shipped, Its a used one that i cant use. Not a bad price for a backup.
 

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Hockeyham This is what you do

If you search my ID for my posts you will see what I have been going through. I had the same problem as you, but finally I got a mechanic that looked up the tech bulletin from GM on what to do after you have done what you have had done. That being said take it back into a dealer and have them pressure test the cylinder by taking the spark plug out and hooking up a test rig. The tech bulletin has them put your cylinder top dead center and inputting 100 psi shop air into the cylinder through the head. Now if the gauge reads less than 75 percent you have a head problem, or a ring problem

The acceptance criteria for cylinder leak by is 25% if it leaks more than that you most likely have a valve that is not seating in the head.

Now GM tech bulletin suggests that you replace the entire head and all valves, they know there is problems with 04-07 heads. I hope your is under warrenty becuase the parts and labor for instulation of a new head is around 4000 if the timing chain does not fall off, if the chain falls it goes up to around 6500.

I am telling you get it into a place you trust and have them do this test I am fairly certain you have a bad head.

good luck let me know what happens I have been meaning to post pictures but I have not had time.:eek:
 

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2004 chevy trailblazer_lt
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1 Posts
cylinder 6 Misfire

My 04 TB 6I had a similar issue in which it was idling horribly to the point where I thought it might die. The Service engine soon light was constantly on however when I would accelerate hard or go up a hill it would flash.

When I tried to read the code it didn't work. I thought it was my reader but I went to auto zone and theirs didn't work either. The fuse was blown. After replacing the fuse I was able to get the p0306 code.

When I removed the coil pack there was a large amount of water around the spark plug. I blew out the air and also used some WD40 to remove the water.

The TB is running great again however I am concerned how all that water got down there. I replaced the spark plugs about 3 mo. ago at 110,000mi. I might not have placed the coil pack on properly or snuggly enough but I think I did.

Anyways I want to thank everyone who post on hear because I am not the best when it comes to cars but after reading your posts you gave me some motivation to dive in. I hope this helps anyone who has had the same issue.
 

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2004 gmc
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26,181 Posts
Water typically hits the #5 or #6 plug area after running down the hood when you open it in the rain. Thanks for the report of a satisfying fix.
 

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2003 chevy trailblazer_ls
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5,267 Posts
to add a little more to the open hood/water
apparently for some- the seal around the hood and cowl doesnt seal properly and allows water to fall onto the top of the engine.
the fix for that is an updated rubber seal..
 

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2002 chevy trailblazer_ltz
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18 Posts
Update: My TB still has this P0303 problem, but it seems that the weather has been a big factor in when it occurs. I'm going to try talking to the mechanics about the seal and see if that does the trick. May be a bit before it occurs but I'll post once I've had it done.
 

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2002 gmc envoy_sle
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8 Posts
misfire code

I had the same issues with 2002 envoy 85,000 with a new motor at 42,000. It was hesitating at idle. I did all the basic checks:( except do a compression test first and that would have led me to a bad exhaust valve. Dont make my mistake of taking things apart before doing your homework. If you need to pull the head make sure and use the timing chain tensioning wedge tool.If you dont on the 2002 for sure you will have to take the oil pan down before you can take the front cover off . In order to take the oil pan down you must remove all the 4 wd front components LOTS OF WORK so dont make my mistake!!! :(
 

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2002 chevy trailblazer_ltz
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18 Posts
P0303 mystery solved

I finally had to take my 02 TBLTZ in for repair after a weekend trip where the sputtering got worse and never let up.

Intake manifold gasket (plenum) and the valve cover gasket were the problem. These, plus plugs and a coil and I'm back in the poor house.

And yeah, I did check the prices online afterward...I don't wanna talk about it but I felt slightly shafted. But I'd never have been able to do this myself.

Dunno if this will help anyone down the road, but I did have a couple ppl ask me about it and wanted to pass this along in case anyone else has this issue. I found this forum looking for the solution to my problem, and felt it was the least I could do.
 

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I am going through this same issue right now on one of my family's vehicles. I've got a P0301 which is cylinder 1 misfire. Changed all of the spark plugs, brand new coil, brand new fuel injector, and it still isn't fixed. Previously it has smelled extremely rich, so I thought that the fuel wasn't igniting or that it had a stuck fuel injector. I replaced everything and it no longer smells extremely rich, however it still does misfire every once in a while. Until it misfires the vehicle runs great. I clear the code and it runs great but the code keep coming back and it feels like the car is in limp mode as soon as it's back. I'm out of ideas with this thing. My next step is looking for an electrical demon on cylinder 1 coil and/but/or doing a compression test on the motor. It sounds like I may have to do a leakdown, and I am really hoping for the best in that scenario.
 

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2002 chevy trailblazer_ls
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113 Posts
My wife was complaing of hesitating @ stop lights and stop signs. So @
103K miles I felt new plugs were in order. Then reached deep down and sprung for 6 new coils as well. We need this truck to last another 100K if possible (plus its paid for!). All parts are AC Delco and Delphi

It idles really smooooth now---almost like new! So she took it out a day after all the changes and still saying it wants to shut down on her......like a rough idle. So I took it out for a spin and I get nothing, but smoooth take-offs and no hesitation what so ever.

My question is--- I read how alot of you guys coming up w/"codes"....How can I pull up codes to figure out what's going on w/our TB w/out any check engine lights

Thx!
roland

Also changed out fuel filter and cleaned throttle body when I replaced plugs and coils.
 

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2003 gmc envoy_sle
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5 Posts
This was a good thread for me so I thought I would add my experience with the misfire I had.
I changed the plugs on my V6 envoy @ 165K. After finishing I started the engine and it did not sound right. Checked the codes after noticing the blinking service engine light indicator and it said multiple misfires. So I pulled the coil packs off and reseated them. I noticed during the process that my cylinder #4 coil pack had serious corrosion. I purchased a new one and replaced it. Fired it back up and it worked like a charm.
 

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2002 chevy trailblazer_ls
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113 Posts
I did not know about the aftermarket MM's not having the gel insides like the OEM's do until after I replaced them---I read on this site to never go w/aftermarket MM's----ALWAYS GO W/OEM!!!!

I ordered a set of OEM MM's w/tranny mount from http://www.gmpartsdirect.com/ $160 w/shipping and when I turned on the TB it was like silk! Almost like a new truck!!

There is a great write up on this site on how to go about replacing the mounts

A lot of unnecessary $$$ was spent, but I look @ it this way she paid for and I learned a lot about my TB....hope this helps!

Thanks to everyone who gave their :m2:
 

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2006 chevy trailblazer_ls
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1 Posts
valve seats - 2006 Trailblazer

I have an 06 TB with 114K miles and the check engine light recently came on; it was on for a few days, then off, then on , now off again.

Anyway, just got back from dealer and they said #6 cylinder was misfiring. Changed plugs, coils etc. still bad. Quoted me $5500.00 to replace cylinder hear. Blue book on this is only $4K. I now realize this is a very common problem with this model.

The engine actually runs fine....at least for now. It hesitates slightly on a cold start...for maybe 30 seconds, then runs fine after that.

My question: I do not plan to spend the $5500.00. If I continue to run this vehicle as is, what can I expect? Will the condition worsen? worried:
 
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