1990 Chevy Cavalier idles really fast

BILL12780

MEMBER
1990 CHEVROLET TRUCK

Hello all,
Trying to fix my son's car. 1990 Chevy Cavalier 2.2 4cyl. No idea on the milliage. But its lots I am sure.

Anyway, the the thermostat stuck closed and overheated thus blowing the head gasket.

We surfaced the head and replaced the gasket. Reassembled and the engine started first time.

except that the idle just kept getting higher and higher. It sounds like the throtle is wide open.

after alot of reading we tried to clean the IAC Valve. This seemed to help the first time we started the engine. But the second time it started all over again. So we replaced the IAC.

Still races. Engine run fine and we only had one other problem. During the repair we noticed the belt was getting worn so we replaced. My son drove the car to work (with the bad idle) and the water pump failed. We replace and no leaks no nothing wrong.

Any help or ideas or troubleshooting help is much appreciated.

Thanks in advance
Bill

3 Replies

SERVICE WRITER

MECHANIC
9,123 POSTS

Hi Bill,

IT sounds like a vacuum leak problem. Sometimes you can pick it up by listening for a hissing noise if it's bad enough. You can also spray carb cleaner at suspected areas and listen for an idle change. The cleaner acts as fuel and gets sucked into the combustion chamber from the leak.

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Thursday, January 25th, 2007 AT 6:02 AM

BILL12780

MEMBER
2 POSTS

Thanks for the reply! You have NO IDEA how much I appreciate it.

Yea we tried looking for a vacum leak with the carb cleaner. When we reassembled the intake manafold we were very carful to check the three vacum lines on the TBI. In fact we actually replaced one of them.

My problem with a vacum leak is that it would have to be a big one would it not. I mean the engine is almost running full out like your sitting at a light with the gas pressed to the floor!

Anymore idea's? I simply can not afford to take this to someone. I have about 400 bucks into a 600 dollar car already! :)

thanks again for the response!

Bill

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Thursday, January 25th, 2007 AT 9:41 AM

SERVICE WRITER

MECHANIC
9,123 POSTS

Check the throttle plate and linkage to the plate and see if it's sticking or not shutting all the way. TPS may think it's opened also. Since it wasn't doing it before the work, make sure all hoses and connectors are back on and tight.

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Thursday, January 25th, 2007 AT 4:47 PM