How to?
11-26-2006, 05:29 PM
#1
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How to?
How to test iac valve..Tried having someone turn key didn't here or feel anything at the iac..Car idles real low when cold and misses..But once warmed up like 5 minutes it idles up drive 700 park 1200.
no other running driving problems plenty of power.
I did that key thing even with a piece of hose and got nothing no clicking and tried to feel it and nothing.Strange.
The iac valve is brand new from autozone.
If the iac wasn't working would this be a symptom or would it not idle at all..
no other running driving problems plenty of power.
I did that key thing even with a piece of hose and got nothing no clicking and tried to feel it and nothing.Strange.
The iac valve is brand new from autozone.
If the iac wasn't working would this be a symptom or would it not idle at all..
11-26-2006, 08:03 PM
#2
Why was the IAC replaced initially? Was it diagnosed faulty? If so, the ECM may have suffered damage and can no longer drive the IAC stepper motor.
If the IAC was replaced without diagnosis (on a hunch) the old one may have been good, and the air passages in the throttle body may be the real problem. The ECM pulses each of the coils of the IAC stepper motor alternately. They are pulsed "A" before "B" to retract the pintle (open the air valve) and "B" before "A" fo extend the pintle (close the air valve). The only method to (of which I am aware) is with a two-channel oscilloscope.
You can test the operation of the IAC stepper motor by invoking Field Service Mode at the ALDL socket, then observing the IAC motor action. Unfortunately, this does not help much if there is no action - If it doesn't work, you really won't know if the problem is the stepper motor or ECM.
If the IAC was replaced without diagnosis (on a hunch) the old one may have been good, and the air passages in the throttle body may be the real problem. The ECM pulses each of the coils of the IAC stepper motor alternately. They are pulsed "A" before "B" to retract the pintle (open the air valve) and "B" before "A" fo extend the pintle (close the air valve). The only method to (of which I am aware) is with a two-channel oscilloscope.
You can test the operation of the IAC stepper motor by invoking Field Service Mode at the ALDL socket, then observing the IAC motor action. Unfortunately, this does not help much if there is no action - If it doesn't work, you really won't know if the problem is the stepper motor or ECM.
11-26-2006, 08:15 PM
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Car: 89 RS
Engine: 305 carbed
Transmission: 700R4
Axle/Gears: 3.42 auburn posi
I have found that the easiest way to check IAC is to run the car at idle, and if your car is TBI like mine what you do is move the TPS lever as if the throttle was opening, that tells the pcm to put more fuel and open the iac motor. if the car dies or the iac motor doesn't respond then you know for sure it's not working. only way to check if it's pcm or motor related is to hook up a scanner as far as i know.
11-27-2006, 05:17 PM
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Is the click i should be hearing loud or should i use a piece of hose.
Hmmm if i push in on the iac plug i hear it click but not a steady clicking mor like an all over the place one strange...if it isn.t working would it idle steady 700????in drive then 1300 park.it seems if i push on the valve it will click very faint though.
Hmmm if i push in on the iac plug i hear it click but not a steady clicking mor like an all over the place one strange...if it isn.t working would it idle steady 700????in drive then 1300 park.it seems if i push on the valve it will click very faint though.
11-27-2006, 06:11 PM
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The iac was new when i got the car and it use to high idle then drop now in the morning it is hard to start then 5 min after start idle goes from 550 to 700 and car runs great but thats in drive in park it is 1300 when warm and 700 when cold something seems backward lol thats why i had a question about the wires cause someon put a new plug for the iac in.
Clip
bw gw
bb gb
looking at plug wire side
Clip
bw gw
bb gb
looking at plug wire side
