I had an issue with my 1990 Eldorado missing a while back and determined that it was a bad fuel injector. I replaced the injector and it runs great under load. But now when I am sitting at a light and I am in drive, the RPMs drop down to 525 and the car runs really rough (probably due to the low idle speed). It will idle at about 650 when not in drive. I have tried to figure out how to adjust the idle, but I have not seen anything. The Chilton manual only says that it is controlled by the computer and I cannot adjust it. :banghead: Do I have a bad sensor somewhere then? Any help would be appreciated.

How do you like that, Chiltons was correct. Probably a bad ISC (idle speed control) motor. It does need to be calibrated when installed but after that, the PCM (ECM on a '90) controls and adjusts it.

How do you like that, Chiltons was correct. Probably a bad ISC (idle speed control) motor. It does need to be calibrated when installed but after that, the PCM (ECM on a '90) controls and adjusts it.

I had a feeling it may be something like that. On another note, something that I just thought of. When following the procedure in Chilton for replacing the fuel injector, the last step it stated was to perform an idle learn procedure, but it did not give any instructions for this procedure. My neighbor, who has been a mecahnic for 30 years, did not know anything about this either (he is a diesel mechanic though). Any ideas on that?

It is a lengthy proceedure that Chiltons or Haynes will not cover. You will only find it in the FSM or here maybe (if you do a search). Basically, just drive it and it will "learn" itself as you drive. The proceedure is so the dealer can give it back to you without trying to tell a customer that "the car will not idle right til it learns how" :cynic:

Also let me correct my first post to say that when the new one is installed it needs to be ajusted rather than calibrated. Simple proceedure.

Here it is if your still interested.
http://www.caddyinfo.com/idlelearn.htm