'94 Cutlass Ciera S--Upgrades! Minor problem

[Ardan]

Hello again! Well I had been deliberating and I went with a fairly nice deck first, from JVC. It was about $120 for the deck, and $190 after the accessories needed/service plan/etc. The sound from the speakers is SO much more improved with the better EQ that I won't replace the speakers because it is completely unnecessary . Absolutely fantastic difference with the sound.

I also plan to get the chip as well after all. Anyone have any experiences with it?

However, I do have a minor issue. When idling, it seems to be unstable. Basically, I hear it when i'm in park and just started the engine or i'm back in park, ready to turn it off. It feels like its idling really low and shakes as if its about to kill, but then suddenly surges as if i'm tapping it down a bit. It then goes normal...then shudders and surges again. After that, it just surges and slows repeatedly until I tap the pedal down. If I wait to see what happens, it goes away but still feels rough.

I recently replaced the spark plugs, plug wires, 2 of 3 ignition coils and a PCV Valve. I replaced the valve because a replacement Valve cover came with a PCV valve in it . I had a longstanding crack in the plastic cover. When another relative had the car briefly, a mechanic working on it for her screwed the gasket on it too tight, creating a small crack that oil leaked out of. The new one is aluminum instead, too . I also put the proper amount of Seafoam into there with some more oil after I replaced the cover, and i've seen a big improvement in things. I have also had the fuel injectors cleaned completely, because 2 were clogged!

Do you think this would be the IAC valve at all? The only thing i've heard is that many places say the only common engine issue with the '94 3.1L VIN M V6 engines was failure of EGR passages. However, i'm quite certain that isn't it. The car is TOTALLY perfect in every way now, except for the idle.