1999 Saturn SL2 Fast Idle at 3000 RPM

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ALAKSANSAS
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My son,s 1999 SL2 Saturn with a 1.9 dual overhead cam, 5 speed transmission suddenly began idling at 3,000 RPM. Runs and idles smooth, just very fast, hot or cold.

I have checked for vacuum leaks and found none. Changed the map sensor, did not make a difference.

I can manually control the ariflow with my hand and it idles down fine. I have checked the pcv valve, it works fine. The computer shows no codes.

Any suggestions? We rebuilt about 5,000 miles ago and runs great.
Feb 17, 2007 at 8:53 AM
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SERVICE WRITER
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still sounds like a vaucuum leak, but is there a heavy carbon build up in the throttle body causing in th stick open a little.....or anything keeping the throttle open a little?
Feb 17, 2007 at 8:57 AM
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ALAKSANSAS
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[quote:ceef7f7106="Service Writer"]still sounds like a vaucuum leak, but is there a heavy carbon build up in the throttle body causing in th stick open a little.....or anything keeping the throttle open a little?[/quote:ceef7f7106]

Thanks for your response,
I removed the part of the mainfold that houses the butterfly trhottle valve and throttle position sensor. Cleaned everything, but still doing the same thing.

I also called a local gm service center. They had one doing the same thing, could not figure it out, sent it to Saturn. Saturn service won't give me any help...just bring it in.
Feb 17, 2007 at 9:10 AM
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SERVICE WRITER
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Just for the heck of it........
I have seen a lot of problems with the coolant temp sensor on these and with different symptoms. Cheap to replace, but at least pull it out and look for any cracks on it. it's on the driver's side on that one I believe.
Feb 17, 2007 at 9:31 AM

Suggested Repair

Inspect the coolant temperature sensor on the driver's side for cracks and replace it if damaged; it is inexpensive and known to cause odd idle symptoms. Also recheck for a vacuum leak or anything holding the throttle plate slightly open.

Conversation Summary

A 1999 Saturn SL2 with a 1.9 DOHC engine suddenly idles smoothly at about 3000 RPM hot or cold, with no codes. Vacuum leaks were not found, the MAP sensor was replaced, the PCV valve checked out, and cleaning the throttle body and throttle position sensor area did not help. Blocking airflow by hand brings the idle down. The expert still suspects a vacuum leak or a throttle held slightly open, and suggests inspecting or replacing the coolant temperature sensor.

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