idle air control test procedure

[m_w]

I'm trying to diagnose an idle problem and am suspecting the iac valve could be bad. I can't find a testing procedure in the manual, and I can't find the procedures on the forums either. I thought dave from dmcmw posted a fairly detailed test at one point, but I can't find it. Can anyone help me out?

[sdg3205]

With the car running, unplug the outer idle ecu plug. RPM should spike to 2200 to 2500 if ISM and ecu are doing their job

[DMCVegas]

I ended up with a bad wire on mine for some reason. A solid check would be to check the resistance across all three wires, and ensure that there is none.

[m_w]

sdg3250 got most of the answer I was looking for. I eventually found the thread I was thinking of: http://dmctalk.org/showthread.php?96...idle+regulator

Two fast idle motor tests.

1 - Open up the driver side electrical compartment and locate the idle ECU (the black one on top). Start the engine. Pull out the plug closest to the center of the car. The idle should take off to about 2200RPM. Plug it back in and it should settle down. If this works, the ECU and the idle motor are good.

2 - Remove the hose between the idle motor and the cold start injector. Look down the throat of the idle valve. Have an assistant turn the key to the run position but do not start the car. The valve should immediately open up all the way, and then over about a 30-second period gradually close all the way. This shows that the valve is good, not sticky, and the electronics are working.

I also see I was in Chevy world when I named this thread. I meant Idle Speed Regulator, not Idle Air Control Valve.

Thanks for the help!

[Rich]

I'm trying to diagnose an idle problem and am suspecting the iac valve could be bad. I can't find a testing procedure in the manual, and I can't find the procedures on the forums either.

For testing see info. below in italics. It's taken from K-Jet.org. It first tells you how to check the motor condition via a resistance check on the IAC connector pins. It then goes on to explain how to go after the mechanical end of it.

Dave did mention something about the connectors themselves sometime going bad as I recall. Check the wiring close to the IAC motor to be sure it's OK.

Another way to test the idle air motor is to measure the resistance with your multimeter. A good motor should read +/-20 ohms resistance between any two pins that are next to eachother and +/-40 ohms resistance between the two outside pins.

The idle air motor can be cleaned out if it is not too damaged. The most common way to do this is to detach the motor from the car and spray it out with carb cleaner. Fill the motor with carb cleaner and plug both openings in it. Shake it up and roll it back and forth in between your hands like you are making a ‘snake’ out of clay. You should hear it clicking back and forth. Repeat the cleaning process several times, drain the motor, and then allow it to dry for an hour or so.

source page: LINK: http://www.k-jet.org/articles/information/k-jet-debugging-guide/#41

[m_w]

The Wiring is new (NOS 1983 harnesses in the engine bay). I did the second test in my previous post, these were my results.
- 1st attempt - valve opened slowly and part of the way. Then closed slowly.
- 2nd attempt - valve opened quickly, did not close at all.

Through both attempts (and previously) the regulator was humming loudly and vibrating.

I might try to clean it, but more likely (because of the noise it was making), I'll just order a new one.

Thanks

[Farrar]

Not sure if this is 100% applicable, but I got this from a generic CIS tech book:

Start the engine and make sure the valve is vibrating and humming slightly. If not, check for a voltage signal reaching the valve and check the valve's resistance. With ignition on, the voltage at the harness connector should be approximately 12 volts (battery voltage) between the center terminal and ground, and 10 volts between the center terminal and the outer two terminals. Check the resistance on the connector terminals of the idle air stabilizer valve. There should be continuity between the center terminal and each of the outer terminals. If the readings are incorrect, replace the valve.

The book doesn't mention what the resistance value should be, just that there should be continuity. Sorry.

[Elvis]

If it moves - it is good !

you may want to lube it with some drops of oil - but that's it.

Why a new one ? it's supposed to hum, that's how it works !

I can't find a description what kind of idle problem you have ?
(well, there have been at least 100 here so it won't be anything new)

test of the idle motor:
+12V to the center pin,
Ground to one of the outer pins makes it open or close completely.
You should hear a "clack" "clack" each time you change the Ground-Pin.
Just connect it for a second, NOT permanently !

The Wiring is new (NOS 1983 harnesses in the engine bay). I did the second test in my previous post, these were my results.
- 1st attempt - valve opened slowly and part of the way. Then closed slowly.
- 2nd attempt - valve opened quickly, did not close at all.

Through both attempts (and previously) the regulator was humming loudly and vibrating.

I might try to clean it, but more likely (because of the noise it was making), I'll just order a new one.

Thanks

[glockworks21]

For testing see info. below in italics. It's taken from K-Jet.org. It first tells you how to check the motor condition via a resistance check on the IAC connector pins. It then goes on to explain how to go after the mechanical end of it.

Dave did mention something about the connectors themselves sometime going bad as I recall. Check the wiring close to the IAC motor to be sure it's OK.

Another way to test the idle air motor is to measure the resistance with your multimeter. A good motor should read +/-20 ohms resistance between any two pins that are next to eachother and +/-40 ohms resistance between the two outside pins.

The idle air motor can be cleaned out if it is not too damaged. The most common way to do this is to detach the motor from the car and spray it out with carb cleaner. Fill the motor with carb cleaner and plug both openings in it. Shake it up and roll it back and forth in between your hands like you are making a ‘snake’ out of clay. You should hear it clicking back and forth. Repeat the cleaning process several times, drain the motor, and then allow it to dry for an hour or so.

source page: LINK: http://www.k-jet.org/articles/information/k-jet-debugging-guide/#41

this one reads 10.5 on the pins next to each other and 21 on the outer pins..

?

Dave

[Bitsyncmaster]

this one reads 10.5 on the pins next to each other and 21 on the outer pins..

?

Dave

That is typical for the stock idle motor. The Volvo one is about twice that.