Engine hesitating, I'm freaking out, any ideas?

[scottyb]

2002 C2 cab 6spd, 62k miles

History: I bought the car back in December and it ran fine for a couple months. I installed an EVO intake and a few weeks later it started to run a little rougher than I thought it used to, but I thought maybe this was just more sound from the intake that I wasn't used to yet. Car got hit in a parking lot a couple weeks later and just spent 2 weeks at the local P dealer$hip getting fixed. Pretty minor damage to the rear bumper and engine cover, not enough to cause this problem.

Problem: I picked up the car today and it was raining. Leaving the first few stoplights I noticed that there was a slipping or hesitating going on in the drivetrain but couldn't place where it was coming from. I gave it some more gas and it was definitely coming from the engine. Under partial throttle it acted pretty normal but under heavier acceleration it was jerking and hesitating slightly, like there was one cylinder misfiring. Then the check engine light came on. :huh: I pulled off the road and listened to the exhaust note at idle. It sounds like the left exhaust (right cylinder bank) is rough at idle but the other side is smooth. I could definitely feel some heavy vibration and wavering of the idle when I pulled it off the road.

Since I was not far from the dealer$hip I took it back and am going to have them do a diagnosis on it tomorrow. It got better and smoother as I put more miles on it back to the dealership. But right now I'm freaking out about all the possibilities of what this could be. My worst fear is loss of compression :o or something just as expensive. Best case would be a bad ignition coil or clogged injector. Any other ideas? Why would it act pretty normal under light throttle and get significantly worse under medium throttle? I'm trying to get some answers so I can calm down a bit before I go to bed. Obviously the dealer will tell me something tomorrow, but any educated guesses tonight would ease my anxiety a bit.

Thanks for the help in advance,

Scott

[wross996TT]

OK..first relax...then get the codes read. We will be guessing without codes, but it could be as easy as a MAF (possibly associated with the CAI). It could also be as simple as plugs or coil pack...

[bmohr]

dude, rain and misfire usually spells cracked coil pak. Do yourself a favor and follow the extremely easy instructions on this forum on how to change them out and save a bundle of cash.(P0306, 0304 etc) misfiring codes, just replace the coil pak they point to.

[perryinva]

dude, rain and misfire usually spells cracked coil pak. Do yourself a favor and follow the extremely easy instructions on this forum on how to change them out and save a bundle of cash.(P0306, 0304 etc) misfiring codes, just replace the coil pak they point to.

+1

[scottyb]

dude, rain and misfire usually spells cracked coil pak. Do yourself a favor and follow the extremely easy instructions on this forum on how to change them out and save a bundle of cash.(P0306, 0304 etc) misfiring codes, just replace the coil pak they point to.

Thanks for the help guys. I'm a little calmer now. The coil pack is probably it. I decided to leave it at the dealer yesterday because there were a couple other things that I wanted them to check with their computer. They called today and said it was a #4 cylinder misfire code. Not sure exactly what number yet, but I'll find out when I pick it up tomorrow. It's due to have the spark plugs replaced anyways, so I'll check out the coil packs and replace those at the same time.

I thought of the MAF at first too since I had just done the EVO intake, but then realizing that it was only one cylinder having the problem the MAF didn't make sense, but thanks for the quick response wross.

I'll be resting a little easier tonight, thanks again.