Hey guys,

I got a '93 S10 Blazer with the Vortec and I am trying to track down a misfire at cruise and idle problem.

I am thinking a sticky IAC at this point due to better running when it is colder outside, an occasional burst of engine speed after the engine tries to return to idle (only cold) and the rough idle.

If I just touch the gas it smoothes right out however wanders a bit. On days when it is misfiring, i get a surge with medium throttle going up a hill. When its running good I don't.

Occasionally when I start it, it seems like I can feel each cylinder starting. Meaning that it is very rough and very slowly climbs up to speed.

Over the last year I have replaced the entire ignition system, a fuel pressure regulator, all upper gaskets, and a malfunctioning IAT sensor.

Changing the IAT sensor changed the problem to a occasional miss from a "annoying to drive" I'd say a 98% improvement.

Compression, fuel pressure/leakdown, and vacuum are all ok.

Thanks for any ideas,

Mark