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Red
Red, Auto Service Technician
Category: Car
Satisfied Customers: 147
Experience:  ASE Certified with 20 Years of Automotive experience.
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2001 Saturn SC1 idle fast

Resolved Question:

Occasionally it idle fast 1800-2000 but it will reset back to normal if I turn off the engine and restart. Any idea what would cause that?
Submitted: 10 years ago.
Category: Car
Expert:  Red replied 10 years ago.
Hi

I would check for vaccum leaks. Also check the intake-manifold for the gasket leaking.

You can use carb - or brake clean and spary around the intake and if the Idle picks up then you found the leak. I have replace a few intake-manifold gaskets for this.

You also need to check the IAC to see if its sticking. The best way to check it and test it is with a scan tool.
Customer: replied 10 years ago.
Reply to Red's Post: If its a vacuum leak why would it reset when restart? The vacuum leak won't repair it self and it does not expalin why it only happen from time to time. If its a leak, it will be consistant.
Thanks

BTW. what is a IAC?
Expert:  Red replied 10 years ago.
The car I fixed would do the same thing as yours is doing. I would stait up and it would run ok and then the idle would start to go up. I started to look for a vacum leak. It was hard to find.

The IAC is Idle air control. They can start to stick and do the same thing. The only way to check it is with a scan tool to check the IAC counts and you can run tests on it to see if its sticking open. Start with looking for a vaccum leak if you don't find any then look at the IAC.
Customer: replied 10 years ago.
Reply to Red's Post: That still does not explain why an vacuum leak can be sporatic? A vacuum leak will be consistant and I should not be able to restart and get back the regular idle. Vacuum leak does not heal itself.
Expert:  Red replied 10 years ago.
ok I'm sorry for being miss-leading on the high Idle. Start with trying to clean the IAC.
use some carb spay to clean the valve and port. when you remove it or unplug it do not turn the key on untill its plued back in. If that helps then I would recommend replacing the IAC.

Sorry Red
Customer: replied 10 years ago.
Reply to Red's Post: Where is the IAC and how could I find and identify it?
Thanks
Expert:  Red replied 10 years ago.


Locations View


IDLE AIR CONTROL (IAC) VALVE


REMOVAL



  1. Ignition Off.
  2. Remove air induction tubing from throttle body to air cleaner.
  3. Disconnect IAC valve harness connector.
  4. Disconnect TP sensor harness connector.
  5. Disconnect MAP sensor harness connector.
  6. Remove IAC valve attachment screws and IAC valve. NOTE: The IAC valve is an electrical component and must not be soaked in any liquid solvent; otherwise damage could result.
  7. Remove O-ring from IAC valve and discard.

INSTALLATION


  1. Clean IAC valve seating surfaces on the throttle body to assure proper seal of the new O-ring and contact of the IAC valve flange. IMPORTANT:
    • Before installing a new IAC valve, retract the pintle using the Scan tool. Refer to Scan tool user guide.
    • Normal wear of the IAC pintle, characterized by a ring around the cone, is not an indication of a bad IAC valve.
  1. Lubricate new O-ring with clean engine oil and install on IAC valve. NOTE: If replacement is necessary, be sure to replace with an identical part. IAC valve pintle shape and diameter are designed for specific applications.


  1. Insert IAC valve in throttle body.
  2. Install IAC valve attachment screws using thread coating, Saturn P/N 21485277 (Loctite 242(R) Threadlocker or equivalent). Torque: Idle Air Control Valve: 3 N.m (27 in-lbs)
  3. Connect IAC valve harness connector. Push in connector until a click is heard and pull back to confirm a positive engagement.
  4. Connect MAP sensor harness connector. Push in connector until a click is heard and pull back to confirm a positive engagement.
  5. Connect TP sensor harness connector. Push in connector until a click is heard and pull back to confirm a positive engagement.
  6. Install air induction tubing from throttle body to air cleaner. IMPORTANT: The PCM will have to go through an IAC relearn process once the new valve is installed. The vehicle should be run at normal operating temperature while varying the engine RPM slowly between 3500 rpm and idle two or three times.


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