1990 Chevy Lumina 3.1 engine
 

I have intermitant problems with the idle. Sometimes when I start the car it is on high idle and the car will pick up to 20 mph with my foot off the gas pedal. Then when I come to a stop the car is still on high idle. Then sometimes the car will hesitate when coming away from a stop and sometimes it will even die. When the car is in nuetral the engine will idle very fast and it shifts into drive or reverse to strong because of the rpm's of the engine are to high. There is a idle air cylinoid (I am not sure what this part is called) close to the front of the air intake manifold I unplugged it and the car then started running very rough. I plugged it back in and the car still ran rough until I started to drive and the rpm's picked up again and the car got up to 20 mph on its own with my foot off the gas pedal. Now the car seems to be running okay. It is an intermitant problem and it is hard to diagnose what the problem is.

RE: 1990 Chevy Lumina 3.1 engine
 

I also forgot to mention the engine has been doing a lot of pinging under a slight load. This is a new rebuilt engine with a little over 3000 miles on it.

RE: 1990 Chevy Lumina 3.1 engine
 

If it is running a high idle you should check your throttle positioning sensor. I could be several other things, but I can't think of them off the top of my head. Check your vacum lines too. You may want to see if your throttle is sticking on the throttle body too. It wouldn't hurt to try some WD-40 or something similar. The knocking could be a knock sensor, or something not getting oil, what is your oil pressure at?