cold idle issues

[Slow91z]

I have seen where the CTS sensor reads correct, but what about the IAT??

 

[JDSfastGN]

As you increase load the IAC increases. Example you turnon lights, turnon the AC, cooling fans kick on, etc. This is why base IAC numbers should be above zero.. anything is fine as long as not zero.

Coolant temp will vary IAC reading as the IAC opens to allow more air in and raises the idle to warm up the motor. That is why I asked about the coolant temp sensor and its reading when cold. When cold.. the CTS= ambient temp. If CTS=ambient.. then its an IAC issue plain and simple.

IAC issue = bad IAC, bad mount, computer, chip.

PS.. I have never had success with non-delco IAC's. It should be black in color.

Hmm the coolant sensor reads correctly. Thanks for the help Razor, i guess i can't be much help till I get the thing running again and post up the PL file. It is a delco in there right now and is black.

Have you had this problem since it was "worked over and rebuilt"? After everything you have checked, changed and swapped wouldnt it be good to go back to the core of the problem: the housing i.e., the throttlebody itself and see if thats the issue. Let us know.

Very curious about this one........Subscribed.

I have sprayed carb cleaner all around the TB and cleaned the IAC part of the TB but I honestly do not remember if this is when the problem started. It was so long ago that I don't even remember when it first happened. Sad I know. I went through my parts bin yesterday and picked out a stock TB im gonna throw on when I get it running again.

I have seen where the CTS sensor reads correct, but what about the IAT??

Yes it does. It was recently relocated to the upper plenum as well.

When i turn the key to the on position,engine off the IAC on the scanmaster reads 150.

After starting the engine the IAC drops rapidly to 100 and then continues dropping a number each second until it gets to 80 then it drops a number every 3 seconds until it reaches my set point of 22 on the IAC. The engine idles very good during the time the IAC is making it's adjustments down to normal idle / engine temp.

IAC 22 and TPS .42 at normal engine temp. BLM's at 128 idle and cruise.

This is with the temps in the lower 30's here in Ohio.

Since i do all my driving at night i make my adjustments to the IAC,TPS with the headlights on since there is a difference in voltage with the lights off and will effect the readings.

Thanks, I know mine does similar but drops to 000 instead of hanging around 20. I wonder if there could be a wiring issue or something and the IAC is not even working even if its a new unit.

 

[Razor]

If you hae a spare TB laying around, use the IAC mount with a delco IAC motor installed and you can look through the holes and verify operation. When you start the car it is suppossed to suck into itself. Then as the car warms up.. it extends to reduce IAC.

Dont know of any other way to confirm proper operation. two wires move it.. two wires tell the ecm where its at position wise. That is why there are 4 wires on it.

 

[JDSfastGN]

Bringing this back from the dead, ive finally got around to playing around with it. I swapped throttlebodies but before finishing the swap i took the housing off so I could watch the IAC move. When I took it off the IAC was fully extended into the housing. Key on and it stayed extended? Is this how its supposed to be? Before I reinstalled the new TB I compressed the pintle into the IAC and when I fired up the car it started immediatly and ran.... first time its ever done that. I turned it off and restarted and same old crap. It didn't want to run, although it was better than it was before. I checked voltage and two of the prongs had 12 volts and the others were grounds. I guess I am going to try another IAC with this throttlebody and see what it does. Thanks guys

 

[Razor]

I can tell you i've had issues using non-AC Delco IAC's with a Buick.

The ones I like are the black bodied ones.. in the AC Delco box.

When you turn the key on, its suppossed to extend. As this shuts of air. Then as it starts.. it will retract to let it idle. As it retracts the idle goes up.

Lastly, the IAC uses a stepper motor. two wires are to sense position.. two wires to move it. Careful messing with it as it can damage the computer. On the cars equipped with a FAST XFI.. you'll blow the computers driver if its not plugged in.