I have a 92 grand am with a 2.3 dohc, I recently replaced spark plugs (3 months ago) had a miss so replaced plugs this past weekend, and coil pack, still has a miss when it sits and idles. It sometimes starts rough. Was so told that one of the spark plugs (#3 cylinder) has never fired. Baffled as to why it still has a miss, mapping sensor was replaced a month ago. Also there no check engine light.

SOURCE: engine stalls

your on the right route but also check egr valve

SOURCE: 91 LEGACY STARTED RUNNING ROUGH

The cylinders are numbered as on the spark pack you changed. You might have done better putting the seafoam in the tank as an injector cleaner. Not sure why you changed so many parts, you seem to know how to get the codes from test connector lead hookup and the blink pattern. You might also want to check the fuel rail pressure and the crank and cam angle sensors. Before replacing the injector, swap the #4 injector with the adjacent one and see it the code moves with the injector or stays put. If the code stays on #4, then check the injector wiring, if it moves clean or replace the injector.

SOURCE: miss fire on cylinder 1 and 2 coils replaced

have u put a new set off leads on it as mite be brakeing down under pressure

SOURCE: 03 JEEP wrangler Rubicon 4.0L missfire on cylinders 1,2, and 3!

bad fuel pump can cause this or plugged fuel filter but i believe they are one unit

SOURCE: My 1996 Ford F150 4.9l 5spd. rough idle, poor drivability, stall

try replacing the throttle position sensor