[mrriadh]

My friend's car stalled, found the ICM was flaky, had it replaced. Then he began to experience some sluggishness and overall lack of power (no codes yet). He replaced the plugs and wires (AC Delco plugs and Delphi wires) but prior to installing them, cleaned the intake system (3M intake cleaner) and clean the throttle body. After the cleaning and the install, the vehicle started misfiring (P0300) but it eventually smoothed out and became less frequent. He later replaced the coils and the power was restored with the exception of a misfire at around 2500rpms.

He got the first P0300 code last year, did not get it fixed. Now the code comes back. Please help!

Random misfires that jump around from one cylinder to another (read: P030x codes) also will set a P0300 code. The underlying cause is often a lean fuel condition, which may be due to a vacuum leak in the intake manifold or unmetered air getting past the airflow sensor, or an EGR valve that is stuck open.