Re: 4.3 Cobra sputtering after key turned off
Most carbon build up in older engines is caused by oil getting past the rings... in an engine of this age that has spent all of it's life at the top of the RPM scale, the probability that carbon is causing the issue of run over is significantly higher..
Also, as Idle said, if the timing is off enough to cause "flame over" after the ignition is shut off, could also be the cause.. but none the less, SOMETHING is causing the fuel to continue to ignite after the coil stops producing spark... fuel, efi, etc normally do not weigh in as said unless we are talking about modern computer controlled engines, which more than likely doesn't have much weight on an engine made between 1986 and 1993 - that is carburated, and most likely has points...
Carbon build up from overly rich main jets, leaking carb seals/blown power valve or failing rings is most likely the culprit. If nothing else, I would consider richening the idle a/f to try and cure the run over if the idle circuit is lean, it can cause this issue also...