88 Grand Am Rough Idle

[nuarctable]

Hi all. New to the forums, but I like what I see so far.
Wish I had found this place for all of my previous problems...

Anyway, Ive got a 1988 Grand Am, 2.0L Turbo. 123K miles. My daily back and forth to work car.
All of the sudden it started to idle really rough like its running on 3 cylinders. And it sounds really bad through the exhaust.
And its not all the time.
I can start it up in the morning, and it runs fine, I drive it for 30 minutes at highway speeds 60-65 mph, and come to a stop light, and its idling rough. Light turns green, I go a few blocks, and its fine.
Somedays it may only do it once or twice, others not at all.
Sometimes I start it up and it runs rough, and after the highway driving its fine.

New fuel pump, fuel filter, plugs, and wires in the last 8 months.
PCV looks good, and rattles when shaken.
Fuel injectors sound OK (the old trick of using a long handled screwdriver, and I can hear them clicking).

Could it be something electronic with the computer module?
A plugged catalytic convertor?
EGR valve?

I running out of ideas, and any help would be greatly appreciated.
Thanks

[randy78]

try cleaning the IAC and the EGR of and out, clean off carbon

very common issue with bad idle

good luck