Harmonically

I've already searched this topic but haven't been able to figure out the problem. I started off getting idle misfires. Only when coasting to a stop out of gear, or just sitting in traffic. Never under load. Also, it doesn't happen consistently. For instance, I got a code twice on my drive home the other day and cleared it both times with my aeroforce, but the last two days where I had to drive city/hwy for 250 miles I didn't get a single code.

So far I've swapped out my old battery for a new battery (Possibly low voltage?). Didn't fix it. Changed the plugs with NGK's, gapped two steps colder, as I'm running higher boost. Still didn't fix it. Checked for boost leaks, no dice. It runs great under throttle, full boost no problem and pulls just as strong as it did while ago. Mods and tune have been good for over a year and nothing's changed. I don't drive the car hard either.

Mods:
TR-10 Intercooler
Hahn hard charge piping throughout
23 PSI HPtune
CAI
Hahn 3" catless DP
Muffler delete
KY Stage 3 clutch

Any thoughts? My only other thought, which seems to be a long shot, is alignment issues. I know the crankshaft position sensor is what throws the CEL for misfires like this, and I've been getting TPMS errors with the CEL for misfires. They don't always coincide, but 50-70% of the time I get them both at the same time then they go away.

BoSStwick

I remember when my Cobalt was misfiring. I tried everything but alter my tune, when I did change it, all my misfires disappeared. Just an idea

YelloEye

iTrader: (3)

GM replaced my head citing sticky exhaust valves and a cracked valve seat for my warmup misfires, no dice.

Harmonically

That's my next step. Seems odd though, I've been running this tune forever and haven't had any problems. Trying to figure out other alternatives first.

kzak104

iTrader: (1)

put in stock plugs

Harmonically

They're still stock plugs, just gapped colder. Still the Iridiums.

Anyways, figured out what it was. I WAS getting spark blowout. The colder plugs solved the random misfire. I also had a coilpack on cylinder 3 go bad. Fixed both and now it runs great.