I have a 89 firebird that has an issue with it's idle jumping from approx 900rpm to 400 rpm when at a stop while in drive. Normally it'll idle fine while warming up in park and the rpms are constant while the car is moving. This is quite annoying when at a light lol. I remember seeing a post somewhere saying that it might be a bad ECM (some resistor or such went out) and that it would fix it. I just can't find it for some reason. I've got good spark and fuel, but i don't have the ability to see if i'm just dumping fuel into the cylinders. I sure can smell something rich though so i belive it is. Any ideas?