Hi everyone I am new to the forum and having some issues with my car. I bought an 86 trans am 5 speed Rochester carb a couple days ago. The car had been running pretty good but tonight I got bored and decided to take a look at the air intake. I took the thing off and looked at the carb a little to just see what kind of shape it was in and then started the car with the stock intake off and then it started to idle high at like 1500 to 2000 rpm. It did the same thing with the air filter back on and after driving it home 5 miles I went to shut the car of it started dieseling bad. so much that I just stalled it out on purpose just to get it to shut off. Im not positive what is causing the high idle and I need help. I appreciate all the advice. thanks guys.

 

I have a 86 iroc with a 305 and it does the same thing. It will run good and after a I drive it for a wile the idle will go up to 1500-2500. Then when i turn it off the idle will go back to normal (after I start it again), then it will do it all over again. ?????

 

any fix for the dieseling?

 

Sounds like you have a vacuum leak. Are you running the stock air cleaner assembly? If yes, does the air cleaner snorkle have a vacuum operated door in it? If it does, you need to plug the port on the carb where the vacuum line for the door connects.

 

that's the first place I would look. there is a rubber tube on the air cleaner that goes to the front of the carb. Should be easy to see. Unplugged it causes a vacuum leak in the carb and will cause your high idle issues. Provided you've touched nothing else? the car diesels because of the high idle. Fix the idle, you'll fix the dieseling.