Which sensor for idle dropping when AC compressor comes on?
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Postmaster
Joined: Jun 2001
Posts: 2,809
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From: Loveland, CO.
Which sensor for idle dropping when AC compressor comes on?
The idle drops to about 450 when the AC compressor kicks in, almost enough to stall it but not quite. It just drops for a second, and then goes back up to normal. The truck is in good tune and running well, I am pretty sure that it is a sensors (1990 5.8 auto, fuel injection).
I think that there is an IAC (idle air control) and TPS (throttle position sensor). Is that correct? I am not so good with all of the sensors etc. Where are they located? I am thinking just to replace both, as far as I know they are original with 126K. If they just plug in and out easily, I will replace both. Whaddya think; or is there another sensor for keeping the idle steady when the compressor kicks in?
I think that there is an IAC (idle air control) and TPS (throttle position sensor). Is that correct? I am not so good with all of the sensors etc. Where are they located? I am thinking just to replace both, as far as I know they are original with 126K. If they just plug in and out easily, I will replace both. Whaddya think; or is there another sensor for keeping the idle steady when the compressor kicks in?
Junior User
Joined: Aug 2004
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I believe it is the IAC. It is mounted just behind where the air intake hoses mount to the throttle body. It is held on by 2 scews and has an electrical connection. Regardless of what it is called I had the same problem My 88 Bronco died whem I turned on the a/c. That is the sensor that I changed and it fixed my problem. Hope this helps.
Elder User
Joined: Oct 2002
Posts: 573
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From: Medina, Tn.
Also, the throttle position sensor is on the underneath side of the throttle body, just below the IAC. It is black and I think has to wires. Mine was not adjustable but some models are. I don't think that your 90 is either. Can't remember the price but do remember that it had to come from Ford. Either way, wasn't too expensive.
Good luck,
Good luck,
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Postmaster
Joined: Jun 2001
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From: Loveland, CO.
I think that I will replace both, and clean the throttle body too. At least get the throttle body cleaner and spray it real good inside, it's pretty cold today and I do not feel like taking it all apart.
I could try to get codes, but they would probably tell me what I am already guessing, if there are any.
I could try to get codes, but they would probably tell me what I am already guessing, if there are any.
Lead Driver
Joined: Sep 2002
Posts: 9,182
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From: Gateway to the West
There is also a diode and resistor that sends a signal to the PCM when the A/C is turned on so that the PCM knows to compensate for the additional drag on the engine at idle. The PCM needs this signal or it will not adjust the IAC to compensate. I believe its a module somewhere in the A/C-heater control.
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Postmaster
Joined: Jun 2001
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From: Loveland, CO.
The IAC valve did the trick. I didn't install the TPS because I could not get to it without removing the throttle body, and I did not have a (throttle body) gasket handy. But after the new IAC was in, the idle no longer dropped when the compressor kicked on.
Tell ya what though - between the new IAC, cleaning the throttle body, and the new dist. cap/rotor/wires that I have been meaning to do for some time, the truck idles like a new Cadillac! I thought that it was smooth before, well, it was; but this is smooth like you feel like it stalled when you come to a stop because you can't feel the motor. Really nice!
BTW - Greystreak, I'd still like to know about that module that you are talking about, if you can think of the name of it and exactly where it is. I'd like to replace all of these sensors and stuff eventually.
Tell ya what though - between the new IAC, cleaning the throttle body, and the new dist. cap/rotor/wires that I have been meaning to do for some time, the truck idles like a new Cadillac! I thought that it was smooth before, well, it was; but this is smooth like you feel like it stalled when you come to a stop because you can't feel the motor. Really nice!
BTW - Greystreak, I'd still like to know about that module that you are talking about, if you can think of the name of it and exactly where it is. I'd like to replace all of these sensors and stuff eventually.
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