3100 missfire

[nitz]

I'm having a problem that occurs on start-up in open and closed loop operation. Upon start-up the engine misses. I then get a po304 or po301 code. I have changed the plugs wires and the 1, 4 coil. I still get the missing on start-up but not all the time maybe once every couple of days. If I turn the engine off once I feel it miss and then start it up again it stops missing. The car has 179,000 miles on it. Could this be a mechanical problem? Other than this problem the car runs great. If anyone has had this problem or has any suggestions please help!!

[dean B]

I would do a compression check on all cyclinders and find out if its mechanical

[v6h.o.]

Ignition Coil. or a bad Ign module, cyl's 1 and 4 share the same coil.

did you replace the plugs as well? if you had carbon tracking from a bad set of wires, the plugs should get replaced as well.

im betting its an intermittent module or a bad coil.

try swapping the coil from 1/4 with one of the other coils, watch to see if the missfire "follows" the coil to the new cyl's spot. if it does this then its the coil.

if it stays the same 1/4 cyl's with a different coil, its probably the module.

[nitz]

I'll give it a shot thanks for the info

[nitz]

Well I drove to work this morning with no problems. Came back out an hour later and started it up and it started missing really bad. I pulled the coil off to inspect it and there was a crack from top to bottom. I purchased it from napa hoping to get a qaulity product. I brought it back and they gave me my money back which was cool. I then went to Chevrolet and picked up a coil, installed it and no problems so far. Thanks for the suggestions.