Thread: Idle Air Control Valve - Stepper Motor

Perhaps you should read the manual. The hex near the throttle blade on teh inlet manifold is only to adjust base idle. The idle speed is set by the ECU via the stepper and the ECU will always try to idle no load at 750-800 and in D at about 600-650. I have not seen a stepper with a plastic cover. My guess is that the cover was to protect the stepper in transit, but there are many aftermarket ones around. Usually they just have a cone shaped black plastic end on a shaft with a visible spring. Idle MIXTURE ( despite what you may read on British V8) is controlled by a screw in the end of the MAF and should be set using a CO meter. To lean you turn the screw anti clockwise but only in conjunction with a volt meter and it should be =-1Volt. No wonder you are having trouble. Regard sPhilip A

Thanks for the quick reply. However, using a Mac with the Rave doesn't compute, ergo the "silly" question. Being obtuse is not becoming, and if we want to share our combined knowledge on these matters, constantly referring to the manual (which not everybody has) is not particularly helpful.

I will check all the above tomorrow and let everyone know how it went.

Cheers

Greg

Greg,
I don't think my answer was "obtuse".
ie

obtuseness = # dullness: the quality of being slow to understand
# the quality of lacking a sharp edge or point
This more applies to your question.

Maybe My answer was "ironic"

humorously sarcastic or mocking; "dry humor"; "an ironic remark often conveys an intended meaning obliquely"

I told you gently that the stepper does not have a cover . This should prompt you to try to take the cover off. You may then find it may idle correctly but you have now probably wrongly adjusted the base idle so it may not. So then you have to reset the base idle. There is a series of posts on this from about a week ago and the manual sets it out.

You then talk about the MAF. I too have read all sorts of things here about the MAF but AFAIK there is only one way to do it ie set the voltage (mixture) by adjusting the screw on the end while the engine is idling to get an idle CO of 0.5%( max legal) to1% or therabouts. Usually a voltage of about 1volt gives somewhere around the correct mixture but this is not necessarily so. This also affects the mixture throughout the rev range.

Nearly all mechanics will have a CO sniffer and if you have some sort of relationship will set it for you cheaply. It is not something to play around with.
Regards Philip A

Although it can be set with DC voltages, it is far better to set it with a gas analyser to get it spot on. Voltage reading on a MAF will provide an approximate guide and will get you out of trouble, but to set it correctly you need a gas analyser in the tail pipe to be able to accurately adjust the CO level reading.

Gunson's latest digital gastester will do the job and is available cheaply online from Dominion Tools for about $150 plus postage.

ok, here it is, when I take the red plastic cover off, the engine revs to 1500 and screwing the idle speed adjuster all the way in does not reduce the idle speed.

I think the previous mechanic put the cap back on to give it some sort of stable base. It obviously stops the stepper from working, which is why it just sometimes cuts out and dies. Maybe the stepper is u/s and needs a replacement. I have taken the stepper apart, given it a great clean with cleaner, so I don't know what to do next.

Cheers Greg

Looks like they cut off some poor dog's appendage. have a look at this . It may help. But i think someone bogied it and you may need a new one. 1999 Chevy Silverado IAC motor Regards Philip A

Ahhh, the thick plottens..... thanks for that, will do the test, apparently it should pop out into your hand if you turn the key on and off a few times.

Will let you know what the verdict is.

Cheers

Greg