H3 P0302

[06 H3]

I keep getting the check engine light again. It went away for a while but now it comes on if I sit at idle and it idles rough from time to time. Scanguage says P0302 which is cylinder 2 misfire. I am at 82k miles but I really am closer to 90k because I have been on 35s without the pcm tune to fix the right tire size yet.

has anyone had major issues with the cylinder 2? I will go to the chevy dealer and have them look at it but first should I just change the plugs? They are still original. Any help appreciated.

Last time I checked the plugs I had just cleaned them a bit but were dirty back at 78k. Hopefully its just the plugs and nothing major

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[alrock]

There should be a couple of threads on similar issues. Besides a plug change, you may want to try swapping the coil packs, say between cylinders 1 and 2. If the code is from the coil the code should change to P0301 and you'll know you're fix. To keep it simple I would recommend sticking with OEM plugs. 80K-90K from a set of plugs is plenty of use and you'd be changing them soon anyway.

 

[05Mudiak]

Yup just like Alex said with 90k it's about time for new plugs, swap out plugs. If code comes back swap around coil pack just remember where you put the #2 then if it comes back but in its new location change out the bad coil pack. Easy day:thumbs:

 

[06 H3]

Thanks guys, I will look up the OEM # in the back of the manual and change the coil pack to a different cyl to see if thats an issue. I will also probably have to gap them right? .042?

 

[alrock]

Yes, you'll need to gap them. The OEMs are readily available at places like O'Reilly and do not come pre-gapped. Some of the other brands do come pre-gapped.

 

[Zach]

Chris,

If you get the oem/delco plugs, they are already pre gapped.

 

[05Mudiak]

Yeah they are but you alway want to check them. you never know what happened to them in shipping or the trusty parts guy throwing them around.

 

[06 H3]

Just stopped by the local chevy dealer. I dropped off squeaky to get the oil changed and picked up some plugs. Zach you are right they are pregapped, I asked. I will double check though.

One positive of having 5 cylinders...I didn't have to buy 8

 

[06 H3]

For the most part everyday is a good day with the hummer...Yesterday I was dumbfounded though...I went to get an oil change at the local chevy dealer along with the little multi point inspection. Normally everything comes back pretty healthy but yesterday was different. They claim the Brake fluid and power steering fluid needs to be changed...BUT THEY CHANGED IT AT 77k miles, I am at 82 now...WTF. I also bought the plugs and I was told they were pre gapped from the dealership and all I have to do it put em in and I am good. Well I installed them before 100k because I kept on throwing a P0302. cyl 2 misfire. I torqued them down properly and did everything right but now it will idle normal then pulsate like its about to die. WTF?

This has inspired me to do one thing. I am starting a service records binder and keeping track of ALL things done to the hummer. I am going to try and obtain previous records and statements so I can keep track of everything. I have never had any motor issues but now that I am reaching higher miles I want to keep track of any previous problems so in the future I can narrow things down.

As for this current plug issue, it runs fine, no power loss but pulled a P0300 at idle. Check the gap? Throw some seafoam in there? any suggestions? I have pictures and the one bizzare thing I saw was in the first (closest to the grille) cylinder. inside the coil pack it had some white crap and rust on it while the others were gold plated and clean, whats weird is that I kept pulling a P0302 and not a cyl1 misfire (P0301)

Here is the picture of the normal coil pack

Not normal one

Where I am pointing is where the non normal one is coming from...its the first one. Its NOT the one with no coil pack in...that one is fine

 

[06 H3]

Where is peggy the GM rep when I need her :giggle:

 

[05Mudiak]

The white stuff and rust is because water got in there. Also did you check you gaps even though there are pre set. I am pretty sure its a safe bet you have a bad coil. and when it was missfiring originally it was still holding together but now since you pulled them apart and reinstalled them it totaly messed it up. I would swap positions of the coils keep track of which one you put where maybe just swap 1 n 2 or 2 n 3 something like that. Make sure all connections are clean. judging by your pics your motor is really filthy:huh:but do that make don't worry about gaps right now just swap them coils around and make sure everything is clean. use a green scrubby or steel wool or something like that to clean of all the corrotion of that coil. I think it grouds itself throught the on with the bolt not 100% sureonthat though. I say clean everything up swap coils and go from there

 

[06 H3]

Thanks mudiak! You seem to really know this stuff...and yea my motor is dirty lol should I also have it steamcleaned down the road?

I will clean and swap the coils. And keep you guys posted

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[alrock]

Chris, when I bought those same plugs they were not gapped. Unless the box states the specific gap at which they were set I would not believe they were gapped. P0300 can come from many sources and I wouldn't worry about it yet. I would just clean up the issues as you're finding them: new plugs, with correct gap; corroded coil, etc. Might want to consider cleaning MAF and throttle body too if they haven't been done recently. I get P0300s a few times a year and they go away within a day or so. Essentially what I'm saying is address the specifics of that P0302 and as long as you're in there do some routine maintenance.

 

[05Mudiak]

Thanks mudiak! You seem to really know this stuff...and yea my motor is dirty lol should I also have it steamcleaned down the road?

I will clean and swap the coils. And keep you guys posted

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yeah I have messed around with a motor or 2 or hundreds but who's countin it's kinda hard troubleshooting over the net but I try to help as much as I can

I wouldn't steam clean it. I use Simple Green not diluted (someguys use purple power ot purple suff can't remember whats its called purple something) I like the simple green myself , but spray it on a cold motor soak it down good let it sit for 5-10 mins depend how hot it is outside you do not want to let it dry. then use a brush and/or I just use a wet rag and wipe down everything you can possibly wipe down the rinse off with a decent spray Not a 3000psi pressure washer.

 

[Sierra H3]

Misfires

It may not apply here, but I had similar problems with a 96 Oldsmbile. It took a new set of plug wires to clear up the issue.

 

[08SolarFlareH3]

It may not apply here, but I had similar problems with a 96 Oldsmbile. It took a new set of plug wires to clear up the issue.

There are no plug wires on the 3.5L & 3.7L's. They use a coil on plug design.

 

[06 H3]

Solar that diagram is helpful. #1 on the diagram is what I need to clean up. At first I was worried about this being a major issue but after all it will probably be something simple

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[06 H3]

Alright guys its much better! Even though the dealership told me they were already gapped they weren't. H4O > Dealership...You guys were right. I had gapped them and at idle it sounds much better. No more "pulsating." I will take it out for a drive tomorrow but I am sure its fine seeing the idle was that much better.

 

[05Mudiak]

:thumbs:

 

[alrock]

Glad to hear it is better now.

 

[06 H3]

DAMMIT!!! While it was better and the pulsating stopped recently I got the P0302 again...It happened multiple times so I ordered a new coil pack installed it and still threw the code...it feels like its skipping a beat...any suggestions? I wanna get it cleared up so I dont do any long term damage to the motor.

 

[delta88]

DAMMIT!!! While it was better and the pulsating stopped recently I got the P0302 again...It happened multiple times so I ordered a new coil pack installed it and still threw the code...it feels like its skipping a beat...any suggestions? I wanna get it cleared up so I dont do any long term damage to the motor.

I had this issue right after changing my plugs (same code, symptom etc) so I reseated the coil packs again and it cleared itself. Hopefully your new coil pack will fix this for you..

 

[ColoradoH3]

If it is missing at idle and the miss fire goes away off idle there is a pip from gm for valve seat wear from 2006-2010 on the 3.5 and 3.7 that may require a cylinder head! Mine is going in tomorrow it's a 2008 with 57k and needs a head! It failed a leak down test for the intake valves. Just a heads up. ( no pun intended ) I have the pip released aug 2011 if you are interested. Also this miss fire will appear to come and go at times depending on heat and other variables.

 

[06 H3]

great :gaah: How much does this usually cost? lol

 

[M22KLARS]

If it is missing at idle and the miss fire goes away off idle there is a pip from gm for valve seat wear from 2006-2010 on the 3.5 and 3.7 that may require a cylinder head! Mine is going in tomorrow it's a 2008 with 57k and needs a head! It failed a leak down test for the intake valves. Just a heads up. ( no pun intended ) I have the pip released aug 2011 if you are interested. Also this miss fire will appear to come and go at times depending on heat and other variables.

I have that... and have for a couple years. Motor still feels strong under power and the misfire isn't all that bad at idle.