Pontiac Repair: 1992 Grand Prix GTP, vacuum leak, perfect shape

Question
Hey I have a 3.4 twin dohc engine, Runs smooth when accelerating and at idle until after about 6 or 7 miles at an idle it seems to stumble and sometimes stall, it doesn't seem to do  it as bad when the a/c is on. the engine light is not on and no codes seem to come up on scanner. The car has 192,000 miles on it,but it is in perfect shape. Any ideas?

Answer
Hey James:

It can be a bunch of things. you could have an idle control valve that is going bad and it slow moveing or gummed up and when you come to a stop it's not fast enoughto stabalize the idle and causes a stall. The throttle plate could be gummed up and the same problem. the engine could have a vacuum leak and the idle control valve can't compensate for the leak and it stalls. this has to be driven with a scan tool on it and see what's going on when it wants to or does stall. Good luck :)