First off it a '83 gsl
My idle was perfect and I did a few mods to the car all at once so I don't know if these were the cause. The car pulls really hard but doesn't idle correctly (very low and jumpy) and sometimes die when I let the rpm drop down to idle.

I put a test pipe on the car. You know that small pipe that runs from the large cat to the engine? I took it off and replaced it with a racing beat blocking plate. If that leaks could that cause a bad idle?

The car also came with an extra ecu that the previous owner had been wanting to put on for some reason. So I swapped them out and then my engine started to sound weird (purring) on deceleration, then I smelled a electric burning smell and my antenna stopped working. I put the old ecu back on. What the hell is going on here?! haha
-Greg

 

Not sure what all the mods were that you did, but I would look for a vacuum leak first thing. That seems to be the leading suspect when the idle goes South suddenly. Good luck.

 

Last night I came to a stoplight and the idle was PERFECT. Something like 750 rpm I think. It was a perfectly smooth idle and it stayed the whole way home. I tried turning on the heater, radio, high beams, etc. and that didn't even affect it.

I'll see how it goes on the way to work. -fingers crossed-

 

Hmmm, intermittent problem eh? When you were having issues, was it by any chance raining or wet out? A cracked distributor cap or bad wires will act up when wet out, so that's what I'm wondering.

Easy way to check is to look at the engine in the dark, and watch for sparking around the dizzy cap, coils, and plug wires. If it's a bad leak, you should be able to spot it with some luck.

 

It fixed itself! I was playing around with hoses and sprayed some carb cleaner in the vent bowl thing and the next day it worked. I don't think I fixed it because it took a few trips in the car for it to idle right. I don't get it

I did change the cap and rotor with a new set and it didn't affect it. The wires are NGK so I wouldn't think that they are faulty

 

probley some gunk in the idle circuit worked itself out.

carl.