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Old 11-02-2015, 12:58 PM   #1
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Idle problem

Hello everybody
Im knew in the forum, but i follow it. My 1994 GT convertible after start if you turn on the AC and then shift from park to reverse or foward, the rpm go down and the engine shutoff. Sombody told me the piece control that but wsa in spanish (Im in PR). If some body know what is (in engliish) please let me know.
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Felix.
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Old 11-02-2015, 01:01 PM   #2
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Originally Posted by fmlafo View Post
Hello everybody
Im knew in the forum, but i follow it. My 1994 GT convertible after start if you turn on the AC and then shift from park to reverse or foward, the rpm go down and the engine shutoff. Sombody told me the piece control that but wsa in spanish (Im in PR). If some body know what is (in engliish) please let me know.
Regards

Felix.
Does your car have an Idle Air Control Valve separate then the Throttle Body? I would get some MAF cleaner and clean the MAF, TB, and IAC valve. Also check your air filter. Basic maintenance is always a good starting point.

I would also disconnect the battery for an hour or so while you do that. So the car can relearn when it comes back on.
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Old 11-02-2015, 02:24 PM   #3
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I recommend spending a little extra money on a Motorcraft brand Idle Air Control valve if you determine that is the cause of the idle problem.
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Old 11-02-2015, 07:38 PM   #4
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It could definitely be either a dirty IAC valve or a defective IAC valve.When you turn the ac on,the IAC valve is supposed to increase idle to compensate for the load that the compressor puts on the engine.I would remove it and clean it thoroughly with carb cleaner,dry it thoroughly, reinstall then do a base idle reset.The link below will help.If you've already got the idle speed set correctly,you can let the engine idle then disconnect the wiring harness from the IAC valve and the engine should stall.If it doesn't stall,this can be a sign the IAC valve is defective.If you disconnect the wiring harness and connect a ohmmeter across the IAC valve terminals, it should read 7-13ohms.If you reverse the ohmmeter leads on the terminals, it should read infinite ohms because its got a diode inside of it.Leave the harness disconnected,touch the (+) voltmeter lead to one of the IAC valve terminals and touch the (-) voltmeter probe directly to the IAC valve case.Resistance (ohms)should be high.Measure both terminals the same way.If the meter reads 0-13 ohms,the IAC valve is shorted to the case,so replace it.The directions shown below are for a base idle reset.

Disconnect battery & turn on headlights for 5 minutes to erase KAM memory.
With the engine off, install a .025” feeler gauge between the idle stop-screw and throttle lever and adjust for that .025” gap.
Run the engine for about 30 seconds at 2500 rpm.
Return to idle and set the idle stop-screw for 650-750 rpm.You wanna keep the rpm level at or below 750rpm to prevent idle surging & rolling idle.
Turn the car off, restart and let idle for 2 minutes.
If idle is within specification you’re done except that you should pull the IAB connector to see if the engine dies. It should.
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