IACV signal
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From: Houston
IACV signal
I went to the shop and had them read the diagnostic codes from my '89 GT's LH computer. The only fault was "IACV signal missing."
IACV, I have found, is Idle Air Control Valve.
The car idles perfectly (though it used to surge at idle, and I don't know why it stopped).
What effect might a missing IACV signal have?
IACV, I have found, is Idle Air Control Valve.
The car idles perfectly (though it used to surge at idle, and I don't know why it stopped).
What effect might a missing IACV signal have?
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The IAC helps control idle smoothness by metering air, which has passed the MAF, to the back side of the throttle. A non functioning or "sticky" IAC sometimes induces idle "hunting", in bad cases, perhaps "surging". The fueling computer is pretty capable and may have overcome the lack of IAC function. What is your idle at? spec is 775 + or - 25 for the 89 GT.
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Idle is very very close to 775. The emissions inspection a couple of weeks ago showed 776.
My recollection is that the IACV takes a signal from the LH and converts it to a valve opening. What signal does the IACV return to the LH computer?
My recollection is that the IACV takes a signal from the LH and converts it to a valve opening. What signal does the IACV return to the LH computer?
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From: Cambridge England
Q: "What signal does the IACV return to the LH computer?"
A: RPM
"NO IVAC signal sounds like a bad connection or a faulty LH ECU. A common fault. The idle might be OK most of the time, if the idle stabiliser was last powered by the ECU at normal operating temperature.
The problem comes when conditions vary a bit, and the loop would usually adapt the idle. Now it doesn't...............
A: RPM
"NO IVAC signal sounds like a bad connection or a faulty LH ECU. A common fault. The idle might be OK most of the time, if the idle stabiliser was last powered by the ECU at normal operating temperature.
The problem comes when conditions vary a bit, and the loop would usually adapt the idle. Now it doesn't...............
