So one day, I was idling in a parking lot when all of the sudden I notice the RPMs start to drop, rise, drop rise. I take off, I notice a loss of power. I go somewhere else, turn the car off, do my business. When I turn my car back on, the idle is worse, and then an SES light came on. I scanned it for codes, P0300 which is random misfire.

From there, I tried:

1) New ignition module. Didn't help, so I stuck the old one back in.
2) New plugs. Didn't fix it.
3) New plug wires. Also didn't fix it.
4) Cleaned fuel injectors. Nothing.
5) Took the car to Chevrolet to diagnose it. They said cylinder 7 is the one that's misfiring. They tried swapping the plugwire and swapping the injectors around. Didn't fix it.

So, what next? Could it still possibly the ignition module? After that, the optispark? Also, it doesn't misfire as bad when it's cold and gets worse as the engine heats up.

 

first i'd check for spark... take plug wire off and see if it throws a spark... (shouldn't do that with your hands) and if it does then its not your optispark... you need to check it for compression, since you have checked your injectors already.. if no spark then you get a new optispark....hey that rhymed

 

Well, it almost certainly isn't the wire because we stuck an old one on #7 and it still missed, but I might just do that to prove that it's the optispark. UGH.

 

yeah...thats what i meant you to do it for! check it with an old plug and as long as the plug is grounded, that will check all of your electrical components at one time.

 

The other item it could be is the spark distributor. I know more than a couple guys with lt1's that had to get new ones when they got misfires that could not be traced anywhere else.

Hope not, its an expensive piece. Good luck.

 

The Chevrolet dealer has had my car since Monday and they still haven't figured it out. One idea they have is that the intake manifold might be messed up. Is that another possibility?

 

Well, Chevrolet finally decided to go with a bad intake manifold gasket as the problem. I talked it over with a private mechanic who actually knows what he's talking about and he said that a leaking intake manifold gasket wouldn't cause that problem, as it would still be getting air, just not from the intake. So basically, Chevrolet is screwing me over and just telling me something since they had my car for 5 days and couldn't figure out what was wrong.

And now I'm pissed... I get my car back and it takes like 3 seconds to start. It never did that before. Also a bunch of coolant was spilled everywhere under the hood... they really jacked my car up. I'm so pissed @ Chevrolet.

 

When I was having misfiring problems ( of a different origin) my dealership basically did the same run around to me, and as you I spoke to one of the head guys there, and he said they just couldn't find anything. They knew it had a major problem, but they couldn't tell me what it was.