Posted: Mon Dec 05, 2011 12:02 pm Post subject: 2004 impala 3400. p0300 random misfire
Oh its just me again. Long time since I have been around...
P0300 - random misfire
Only happens on cold startup, interceptor guages only really show the misfires on #2, ranges from 50ish to 200ish at a time, only when dead cold. Lasts about 4 minutes sitting at idle, or 2 min if I just start driving. Minor backfiring as well.
During normal driving I get minor misfires (2-4) on all 6, but few and far between, and usually only when at a stop.
Started in the past few weeks since we have been seeing negative temps in the am, but does it all the time on a cold start, no matter what the temp.
Have replaced front plugs and wires, reconnected my egr and took the block off out (which made it worse once I plugged it in, but back to the initial problem once unplugged (its my old dead egr, was just testing))
Have cleaned the maf, throttlebody, and done visual inspections on everything, used an injector cleaner in hopes it was just something stupid.
Car has to go for first inspection ever in 8 days, and it won't pass with the code.
Any ideas? Don't want to dig too deep, as the plan was to pass inspection then sell it off. Been a good car, but I need something else now. If there is a good chance it is the egr (I have deleted all egr codes so nothing is popping up, don't currently have a laptop to re-add all the codes, or do proper scans with the software, relying on my interceptor gagues.)
Threw some injector cleaner in her on saturday and have driven her for 8 hours or so since, no change. I relize it could be the actual injector and not just dirty, but I feel some change would have happened.
I hope it is some cheap fix as I don't want to drop a wackload of cash into. It right before I sell.
Brought it to a shop. Full scan and diagnosis. Nothing found. Pressure tested email everything. Nothing found. Replaced rad cap because he noticed the pressure release was plugged. Misfires dropped to almost nothing.
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