Engine Idle Speed Adjustment

Tiny
STACYP
  • MEMBER
  • FORD MUSTANG
I have a 1987 Mustang GT. The Engine is idling @ 2000 RPM. How can I adjust the idle speed. It is fuel injected.
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Tuesday, May 22nd, 2007 AT 9:46 PM

3 Replies

Tiny
RUDPRO
  • MEMBER
If your car is fuel injected, you probably have a vacuum leak or a bad idle control valve. Check for proper vacuum with a vacuum gauge and check the vacuum lines for leaks. If that's OK, it might be the idle air control valve, or I think Ford calls it the air bypass valve. It should be mounted on the side of the throttle body and it has 2 wires going to it. I'm not very familiar with your car but if the valve is the same as on other Fords, I could tell you how to check with an ohmmeter. What size engine do you have?
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Wednesday, May 23rd, 2007 AT 2:21 AM
Tiny
STACYP
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It has a 302 Engine. I did not find any vacuum leaks and when I unpluged the idle air control the idle dropped down to around 900 rpm.

So I would assume this is my problem, correct?
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Wednesday, May 23rd, 2007 AT 2:17 PM
Tiny
RUDPRO
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It could be the idle air bypass valve or a few other things. To check the air bypass valve. Unplug the electrical connector on it. Put an ohmmeter on the 2 prongs on the valve. It should read between 7-13 ohms. You have to put the ohmmeter leads on the right way, the valve has a diode in it. The positive lead of the ohmmeter should go on the prong closest to the throttle body. Try it both ways. If it reads OL(overload) both ways the valve is bad. If it reads OL one way and you get a reading of ohms outside the 7-13 ohm range it's bad. If it checks good it could be the O2 sensors or the MAP sensor or throttle position sensor. They all give data to the computer to adjust the air bypass valve. You might want to try changing the bypass valve anyway, it probably is the problem
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Thursday, May 24th, 2007 AT 1:10 AM

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