Hello. I am now to this sit and still trying to figure it out. I used the search engine on ThirdGen.org but I couldn't find anything similar to my problem, I just get irrelevant results.

Anyways, I have a 1990 firebird formula 350 TPI and it is idling super high. It likes to stay at 2,000-3,000 rpms and will not go down to 750 rpms like its supposed to even when I push the throttle control on the throttle body. Any suggestions on how to fix this? I've tried the idle adjustment screw but it didn't help much. The car drives perfectly fine so I don't think it's out of time or anything. Thanks in advance!

 

You must have a large vacuum leak somewhere past your throttle body. The engine should not be able to get enough air to rev that high with the throttle blades closed

 

thanks for your response. I will check again for a vacuum leak. Do you think the Idle Air Control valve could be bad?

 

It is also important to use a diagnostic tachometer for any such work, and not rely on the in-dash tachometer looking thing, which is more a part of an accessory trim package than any kind of actual instrument. Those trim pieces are notoriously inaccurate.

 

haha well my car is straight piped so I hear the engine roaring at a stop light. My tachometer works just fine. Anyways I took a look at it and I ended up haven’t a big crack (more like a missing chunk) in one of the intake gaskets. So I replaced it and it works good now

 

One guestion. Does it sound like the engine is at 2000 RPM? I only ask because when my tach started to fail, it started claiming that I was idling at 2000-3000 RPM and was cruising at 5000+.
I did freak out because my engine was kind of loud but I replaced tachs and it turns out I was idling at 1000 due to a vacuum leak. Just a thought.