1997 Ford Mustang bad IAC?

NICK18

MEMBER
1997 FORD MUSTANG
V8
2WD
MANUAL
103,000 MILES

Hi, I have recently purchased this car a couple weeks ago and have noticed that it idles extremely high, and when shifting the rpms hang at about 3 grand. This is annoying because you have to shift really slow, cause the car jerks pretty bad if you dont. I have already checked for vaccum leaks and pulled the IAC off and cleaned it with no succes. I have heard about making a new gasket with a smaller hole for less air flow and was thinking about trying that but im kind of a little leery about it. Should I try it, or just buy a new one? Thanks a lot

Tuesday, February 3rd, 2009 AT 5:18 PM

8 Replies

RASMATAZ

MECHANIC
75,992 POSTS

Get a new one or do below

Here's how to clean the IAC valve:

Disconnect the air intake ductwork from the throttle body.

Start the engine, then increase and hold the idle speed to 1,000 to 1,500 rpm.

Spray the throttle cleaner or engine cleaner into the throat of the throttle body, aiming for the idle air bypass port (usually located on the side or top of the throttle body opening). Give this area a good dose of cleaner (about 10 second's worth).

Turn the engine off to allow the cleaner to soak into the IAC passageway.

Wait about three minutes.

Restart the engine, rev and hold at 1,000 to 1,500 rpm, and repeat the cleaning process again.

Turn the engine off again, and reattach the air intake ductwork to the throttle body.

Start the engine and rev and hold to 1,500 to 2,000 rpm until no white smoke is coming out of the exhaust pipe.

If this fails to make any difference, you can remove the IAC valve from the throttle body and spray cleaner directly on the tip of the valve and/or into the ports in the throttle body. Let the cleaner soak awhile, repeat as needed, then reinstall the IAC valve, start the engine and run it at 1,500 to 2,000 rpm as before until no white smoke is seen in the exahust.

If the idle speed still surges after this, the IAC valve is defective and needs to be replaced.

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Tuesday, February 3rd, 2009 AT 5:34 PM

RUMREDRUN

MEMBER
12 POSTS

I had the exact same problem high idle rpm all of it! TPS Throttle Position Sensor! Make sure to take the screws out carefully and pay attention to which direction the spring loaded sensor turns! Installing the new one you preload the sensor spring exact opposite of removal!

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Thursday, April 4th, 2019 AT 9:52 PM

JOETECHPRO

MECHANIC
705 POSTS

Hey NICK18,

A quick test for your TPS if you can get access to a scanner with live data is to check what the ECM is seeing from the TPS.

You should see a signal around 1V at idle to around 4V at wide open throttle.

If you open and close the throttle you should see a smooth trace from 1V to 4V and back to 1V.

Quickly rules out the TPS and TPS wiring.

Regards, Joe

Image (Click to make bigger)

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Friday, April 5th, 2019 AT 10:51 AM

RUMREDRUN

MEMBER
12 POSTS

Yes True! I was fresh out of high school and my sn95 just dropped warranty when I had the problem. Today the same sn95 has a BAFAX live data running soon as the key is on! For $22.00 the BAFAX is probably my Cheapest Best tool in my shop! I have three of them! My sn95 ol ladies R/T and shop uses. I would and do suggest anyone that turns a wrench often to get one!

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Friday, April 5th, 2019 AT 2:16 PM

RUMREDRUN

MEMBER
12 POSTS

LoL I also didn't realize how Old Most of the post on here are!

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Friday, April 5th, 2019 AT 2:17 PM

JOETECHPRO

MECHANIC
705 POSTS

Hey rumredrun,

I didn't see that either, I guess this fault has been resolved already.

Thank you for the information though, It's amazing what you can do with a cheap Bluetooth OBD2 tool now.

All the best, Joe

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Friday, April 5th, 2019 AT 6:10 PM

RUMREDRUN