I've been trying to nail down a problem in my '89 bonneville where it idles rough after the engine gets a chance to warm up. Looking back in past forum posts most people seemed to say such a problem was most likely coil pack or wire or ICM related. So far I've put new wires in, and I just changed the coil pack last weekend and it still idles rough after warming up. I did notice when I took the old coil pack off that the greenish insulation from the ICM had pretty much melted and collected down at the bottom since it sits at an angle. I had to cut a bunch of it that was stuck to the coil pack off with a knife.

So my question is, is this a fairly obvious sign I should change the ICM? My running theory is that it'* currently getting too hot with the lack of insulation causing my rough idling.

Green goo is not a good sign but does not mean the module is bad. Could cause a bad idle but *in general* if the module acts up, so will the tach. Is it jumping around ?

OTOH if the idle is more erratics (swings up and down) than misfire, that is more likely a gummed up IAC. Scan tool would show the IAC command jumping around.

Are other things that could cause but first describe "idles rough" a bit more please.

that could most likely cure the problem