Intermittent miss at idle.
2004 S-10 Crew Cab
4.3L
236,000 + miles
For months now I've been having a "miss" while at idle. Not a constant miss where the cylinder(s) have no fire at all. It is definitely a miss. Sometimes when stopped at a traffic light or stop sign it's worse than other times. Never has set a code until recently.(PO303) There are other codes I need to mention in a moment.
I have been reading a lot of info on the fuel injection systems on this vehicle but cannot be certain it is the fuel injection.
Things I have done to "fix" this problem are...
Replaced distributer cap and rotor. (old ones didn't look bad to me)
Replaced air filter
Replaced AIC
Cleaned MAF sensor
Fuel pressure regulator leak down test. (passed with flying colors)
Replaced bad alternator just today.
Noticed that the coolant overflow tank was empty and topped off. Radiator was replaced in the last 6 months and there are no external coolant leaks.
Engine oil does not smell of gas but I will double check that.
Also another intermittent problem and probably related is that sometimes it is very hard to start in the morning for the first time of the day. More frequently after it has sat for a couple of days without running.
Fuel pump was replaced a couple of years ago by a Chevy dealership.
Catalytic convertor replaced less than a year ago and pre-cat was removed. The muffler shop said G.M. only used the pre-cats for a couple of years and that I really didn't need it.
List of codes stored currently in the PCM
p0420
p0507
p0303
p0102
Thanks for any advice,
Jeffrey