OK I've read lots of posts on what could cause a high idle. (1000 to 1500 hot in gear). I have a 91 RS with the 305 TBI. It has 161k for miles and runs like a top except for the idle. I just gave it a complete tune up and fixed a couple vacuume leaks and even befor that it was getting 17 mpgh in the city and it is an auto. What controlls the idle? Isn't this thing all controlled by a computer? I sure wish it had a screw that I could back off to lower the idle. The Throttle Body is very dirty but I am a little scared to take it off and clean it. But it should really be done. Can I do it on the car while its running like you do to a carb? I take all the advice I get from this for very seriousally and I will give feed back if some one will help me.

 

Remove the tbi & clean it, it has a base gasket that likes to go bad & cause a vacuum leak. Theres a valve on the tbi unit, its called the idle air control, it controls the idle speed, it might be stuck. Check the gasket first.

 

Well I started it this morning and the idle went to 3k then popped dowen to 1500 then it started to surge and die. It threw a code of 21. Started it again and drove off and in the 7 miles the SES lite came and went 3 time to eventually stay. The idle at a stop lite was 1500 but seemed to run fine besides. I started out with the best intenshions. It was running fine except for a code 32 and an idle of 1000 so I gave it a tune up and now this. Please help I hate to throw more money at it to be disappointed.

 

Once all vacuum leaks and possible faulty sensors that can contribute to the ECM supplying more fuel than required, i.e. O2, or CTS...etc.
Try the procedure in this article.http://www.ehow.com/how_7959677_rese...le-gm-tbi.html
Remember do not adjust the idle screw without following the procedure - this is not a carburetor.

 

Did you check the gasket like I said?

 

I had the same problem with the same engine in my RS. I replaced the TPS (throttle positioning sensor) located on the passenger side of the throttle body, and it ran normal. It wasn't that expensive. Throwing parts at a problem isn't always the best advise. I am just explaining how I fixed it.

 

now i'm pulling code 21. this car is driving me nuts. it's getting harder to start too.

 

Well it porgressivly got worse. I finally just did what I wanted to do and replaced the tps and I'll be god damned it is fixed best 36 bucks I've spent yet. So much for over trouble shooting it and expecting the worse. I need to go back to my old thinking and keep it simple stupid.

 

Ahh! Good to hear. Idling where it should be at about 7 hundred? It wouldn't hurt to check all your vacuum lines, or maybe replace old and cracked ones. Take the air cleaner off and listen for hissing while it's running. It would only be about 5 bucks or so to do this. I just did this, cause I had a hisser (one leaking) behind the air cleaner.

 

I all ready checked and fixed all the vac leaks. Thanks for the sugestion. I was just going to replace the whole tbi but tryed the tps first and it worked. But I still want to clean the injectors does anyone know if I should try this myself or where I should send them? The car has 162000 miles on it and need some tlc but runs great. I need the engine to last till winter and I'll drop a 350 in it then. If I new how to post pictures I would love to show it off. I painted it put a new top on it and re did the complete interior. I was getting 16 mpg in the city but after I do some well needed maintance I expect to get 20. If anyone has any sugestions on what to do to help it survive and run like a champ please feel freee to tell me your story. How many miles can I expect to get on this engine with the proper care befor its shot?

 

You could try the "dealer tune up" method. Use spray gum out carb and injector cleaner and spray the throttle body while it's running, but not too much to to cause it stall. As it bogs down rev the engine at the linkage. It will smoke while you are doing this, but it can be effective.

 

I have new rebuilt injectors and all the gaskets on order to rebuild the throttle body. I allready have a new TPS should I get a new idel sensor too? Is there anything I should watch out for or be carful with? Or anything else I should do?