LS6427

iTrader: (2)

You won't get a code or an SES light until the 02 sensor(s) are totally failed, or until they make the engine run so bad that you won't even want to drive it anymore.

So go get a scan to see what the 02 sensors are doing while the engine is running.

A dirty MAF will effect cold start-up and WOT only. But clean it anyway.

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91RS383

Depending on what it costs you to get a scan, you can buy something like: www.obdcom.com to check your O2 sensors. When the front sensors are working as they should they will rapidly switch from high to low voltage but the average should be somewhere near the middle. Your o2 sims should read a constant 0.45v or right around there.

You can buy specific MAF cleaner in an aerosol can. Use that. Do not touch the tiny sensors that are exposed inside the MAF. They are delecate.

tonydepo

Well, we replaced the crank sensor and that didn't work. My buddy is going to bring a real scanner over this weekend. We drove down the road and now it is misfiring bad and constantly. We are going to check plugs/wires and coil packs this weekend.

TraptLP

iTrader: (2)

Make sure the harnesses on the injectors are completely seated. All of them should "snap" into place. One of mine was barely unplugged and I could barely drive my car home it was misfiring so bad. Just a thought.

LS6427

iTrader: (2)

My PCM ground wire came loose after 8 years and caused terrible misfiring 2 months ago. It basically caused the drivers side cylinders to not fire. My PCM got fried in the process. I just put a new one in last month and it fixed it.

But the culprit was the ground wire that goes from the PCM and attaches to the engine block. 4 little wires come out of the PCM and merge into one, then that larger wire attaches to the block somewhere.

Start it up and grab the wiring harnesses everywhere and move them around to see if things change from crappy to good. Move the fuel injector harnesses on both sides and move the coil harnesses on both sides.

And remember, one bad fuel injector on a side will take out all 4 injectors, if its an electrical issue with that bad injector.

Best way to find the misfiring cylinder......
When the engine is cold, start it up for 15 seconds, then feel each exhaust pipe near the heads. The cold one(s) are misfiring...or not firing. You can also hold a screwdriver on each exhaust pipe and you should be able to feel the "tick" when it misfires.

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tonydepo

Thanks for the help gang. Will check on some of the suggestions tomorrow after work. I will keep you posted.

tonydepo

Can someone tell me what this connector is for? It is the one about dead center that is not plug into anything. Thanks

litle88

iTrader: (20)

If I remember correctly it was for some emissions BS, no worries mine has the same wire hanging LOL.

BUt I have just today started having the same DAMN problem! I have aeroforce guages and they dont detect misfires, SES lights, Knock is 0 I pull all the plugs and the #5 looks like this, all full of SOOT!
So I think I have a leaky injector or a coil going BAD, my brother has a 06 tahoe and Im gonna stop by tomorrow and take one of his and replace it with the one in cyl #5 and see if mine still does the SAME EXACT DAMN thing you have If you like can I keep you posted? I dont wanna be a highjacker but they are the same problems and symptoms!

tonydepo

No problem at all. Getting my msd wires tomorrow at 10 am. I will keep everyone posted.

tonydepo

Everything is running smooth (crossing fingers) after changing my plugs and wires. Some of the plugs looked very bad with a nice build up on them. I put the msd wires in this time instead of a cheap set like last go around. Thanks for all the help!!!!

litle88

iTrader: (20)

Lol, man we must be on the same work schdule. I was typing to tell you I changed the coils and I STILL have the problem! I'm gonna change wires next, even though I just bought these MSD's in October.