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Mike V.
Mike V., Auto Service Technician
Category: Car
Satisfied Customers: 23611
Experience:  25 years of experience, Certified Subaru Technician and Nissan factory trained.
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I have a 99 Ford Taurus SE with an idling problem.

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I have a '99 Ford Taurus SE with an idling problem. When I get going on the road, everything is fine, but at a redlight, drivethrough, etc., the idle begins to diminish and, eventually, the car dies. The only thing I have really done to the system is change the fuel filter (along with all the other general maintenance of oil change, filter, air filter, etc.) What are some things I can do to fix this problem?

Hi there!It is likley the IAC valve.Sometimes it gets covered with carbon and the pintal inside cannot move to make the adjustments.You can usually take it off and clean everything up with carb cleaner and that will allow the pintal to move properly.Here is some info.Hope it helps!Thanks


See Figure 1

Click image to see an enlarged viewFig. 1: IAC valve assembly

The Idle Air Control (IAC) valve adjusts the engine idle speed. The valve is located on the side of the throttle body. The valve is controlled by a duty cycle signal from the PCM and allows air to bypass the throttle plate in order to maintain the proper idle speed.

Do not attempt to clean the IAC valve. Carburetor tune-up cleaners or any type of solvent cleaners will damage the internal components of the valve.


See Figure 2

Click image to see an enlarged viewFig. 2: The IAC can be monitored with an appropriate and Data-stream capable scan tool

  1. Turn the ignition switch to the OFF position.
  2. Disconnect the wiring harness from the IAC valve.
  3. Measure the resistance between the terminals of the valve.

Due to the diode in the solenoid, place the ohmmeter positive lead on the VPWR terminal and the negative lead on the ISC terminal.

  1. Resistance should be 6-13 ohms.
  2. If resistance is not within specification, the valve may be faulty.


See Figures 3 through 9

Click image to see an enlarged viewFig. 3: IAC valve mounting-3.0L OHC (4 valve) engine Click image to see an enlarged viewFig. 4: Detach the IAC valve connector Click image to see an enlarged viewFig. 5: The IAC valve is retained by two bolts Click image to see an enlarged viewFig. 6: Remove the two IAC valve retaining bolts and... Click image to see an enlarged viewFig. 7: ... remove the IAC valve from the intake manifold Click image to see an enlarged viewFig. 8: Thoroughly clean the IAC valve mounting surfaces Click image to see an enlarged viewFig. 9: Always use a new IAC valve gasket when installing the IAC valve onto the intake manifold

  1. Disconnect the negative battery cable.
  2. Remove the air cleaner inlet tube and the throttle cover, if necessary.
  3. Disconnnect the wiring harness from the IAC valve.
  4. Remove the two retaining bolts.
  5. Remove the IAC valve and discard the old gasket.

To install:

  1. Clean the gasket mating surfaces thoroughly.
  2. Using a new gasket, position the IAC valve on the throttle body.
  3. Install and tighten the retaining bolts to 71-106 inch lbs. (8-12 Nm).
  4. Connect the wiring harness to the IAC valve.
  5. If removed, install the air cleaner tube and throttle cover.
  6. Connect the negative battery cable.
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Customer: replied 8 years ago.
I cleaned and checked the AIC valve; the ohm meter read 10.1. When I started the engine back up, I could hear something that sounded like air escaping under pressure. I don't know what the hell is going on here...
I can assume then you are still having problems with the car?If you can hear air leaking then you may have a vaccum lleak.To locate it you can spray carb cleaner around the area of the leak.With the car running this should produce a rise in the rpms.When that happens you will be in the area of the leak.Let me know