My motor takes a long time to idle down. When i completely let off the throttle, it usually goes straight down to 1500 before slowly dropping to where it should be. Sometimes it goes straight down to where it should be with out stopping. When I had a vacuum leak it would idle high and stay high. It doesn't behave that way anymore and after rebuilding the intake, I'm fairly confident that there are no vacuum leaks. I want to know how I can test my Idle Air Control valve for malfunction or a need for adjustment.

Often the iac can be made to perform better by just spraying the area with carb or injector cleaner,better to pull it out and clean the inner area with a cleaner and spray the unit good it is easily removed ,, when cleaning the area where the IAC plugs into use a soft Q tip ,, The tip of the IAC is called a pintle check it to see if it is pitted severely ,even with pitting they normally will funtion properly some times you have to "ajust" the pintle because of pitting 90% of IAC problems are cured by cleaning use care on the area where the small metal rod enters the unit a soft tooth brush can free up this area use care when cleaning and you will most often find you have solved the problem..cover the electrical part and avoid soaking it ,,you will easily see the dirty parts ..do not ajust this part outward retain the original gasket..if replace with non stock gasket make sure pintle does not press against orifice tightly

You must drive the car over 35 mph to reset the ecm and IAC just drive the car normally

[This message has been edited by uhlanstan (edited 07-04-2008).]

My shade tree test for IAC's has been to pull the iac out, reconnect the plug, hold the iac in one hand with your finger(s) also holding the pintel so it does not shoot out of the iac motor. (don't want to loose the little bugger) Have someone start the car and place a finger of your other hand into the iac hole in the TB and simulate the iac to control your engine idle. You can vary the engine speed as you watch the iac drive in and out. (if it is working correctly) If it is working be sure and drive it in most of the way so you can reinstall it.
If you can't do this and make it work you need to trouble shoot what the issue is. You could also log with winaldl while doing this and see what your iac counts are doing.

Just read dodge runners post he knows much more about this than I do .. try to spray it clean first,some times you can just eyeball the hole and see it move
Some times the gasket is shot or the unit is lose (the screw in type),, or manifold gaskets are lose,tighten bolts
This unit is difficult to test electronically,, you need ossiliscope
On the duke the top to TBI may be lose
Many fiero problems are the result of lose wirring ,,so check connections on all units connected to T B I,,a tight clean fit

[This message has been edited by uhlanstan (edited 07-04-2008).]

hey guys dont want to start a new thread on the same subject.

but i went to fire up my 84 2.5 yesterday and get a VERY high idle at around 2100 and so high i had to shut the car down...........after reading countless threads and finding out the IAC could be the main culprit i eventually pulled it out and the pintle/spring is stuck all the way open.

Is the pintle/spring supposed to have some fairly easy play to it?..like able to move it with little force?......because mine is VERY STIFF to move. Takes a lot of force to move it forward and back. How "loose" should that pintle/spring move.

thanx in advance

FFF

The IAC is a stepper motor. Depending on the brand you usually can't move the pintle by hand. On some you can pull the spring back and turn the shaft enough to get it to move. On others you can rock it from side to side while pushing and pulling and get them to move. Some don't want to move at all.
I like to let the ecm move it as discribed above. It's easier to do then it sounds. Having a helper is almost necessary though.

[This message has been edited by Dodgerunner (edited 01-24-2009).]

quote Originally posted by Dodgerunner: The IAC is a stepper motor. Depending on the brand you usually can't move the pintle by hand. On some you can pull the spring back and turn the shaft enough to get it to move. On others you can rock it from side to side while pushing and pulling and get them to move. Some don't want to move at all. I like to let the ecm move it as discribed above. It's easier to do then it sounds. Having a helper is almost necessary though.

ok so they are supposed to be stiff and not move easily at all?........mine was stuck all the way open and seeing it was so hard to move by hand i thought it was stuck open and not good at all.

so now that this is confirmed my next step would be to plug it in and put the key to the ON position and see if it closes?.....or does the car have to be cranked on in order for it to move.

thanx alot

FFF

I'd like to know a way to test the IAC by my lonesome... I don't really have an assistant I can shanghigh, but I'm not sure if the new unit I bought from NAPA is functional or not. I've toyed with the idea of taking a 9-volt battery and connecting it to the terminals... that worked on my electric antenna...

The following is based of course on a clean idle air passage as well as a butterfly that has never been tampered with....

1. Key on Engine off, place jumper wire into ALDL to put vehicle into diagnostic mode ( to check codes )
2. Go to engine bay, you will hear stepper motor moving in the IAC, remove IAC connector. At this point the IAC will be fully closed therby blocking the IAC passage and the car should not start
3a. IF CAR STARTS - Attempt to start car - if car starts and runs then there is a vacuum leak and/or tampered throttlebody and the butterfly will have to be reset.
3b. IF NO START - Attempt to start the car - If the vehicle does not start then the IAC is functioning
4. Reconnect IAC connector and remove jumper wire from ALDL and start car, there will be fluctuations in starting and even hesitation, and in some cases no start as the IAC resets itself.


This test confirms:
- That the IAC is functioning
- test for vacuum leaks
- test for a tampered throttle body

[This message has been edited by Chicken McNizzle (edited 01-24-2009).]

No you can't put voltage on the IAC and get it to move. A IAC had two coils that have to be pulsed in sequence to make the armature step in each direction a 1/4 turn. That is why you have to use the ecm to move it.

If you take the IAC out, jump the AB pins on the aldl and turn the key on it will drive the pintle all the way out and shoot it completely out of the motor so don't loose it. You then have to get it back in though.

when i jump the a+b at the diagnostics port, and turn the key to on..........the IAC moves forward and back slightly........it doesnt shoot out as said in many posts tho.........is it supposed to shoot all the way out no matter what?......does the slight back and fourth movement confirm that this sensor is bad?....

i can force the pintle forward and then test again.....but again it only moves forward and back the same distance. Not sure if this sensor is definitly bad or not.

quote Originally posted by Dodgerunner: My shade tree test for IAC's has been to pull the iac out, reconnect the plug, hold the iac in one hand with your finger(s) also holding the pintel so it does not shoot out of the iac motor. (don't want to loose the little bugger) Have someone start the car and place a finger of your other hand into the iac hole in the TB and simulate the iac to control your engine idle. You can vary the engine speed as you watch the iac drive in and out. (if it is working correctly) If it is working be sure and drive it in most of the way so you can reinstall it. .

thanks dodgerunner, after reading this 500 times i finally get what you are saying. your finger controls how much air is going into the throttle body and the ecm tries to compensate for that by moving the pintle. thereby confirming that the ecm and the iac are functioning correctly. now off to do the test
jon

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I'm the original owner of a white ' 84 2M4 purchased Dec 10, 1983 from Pontiac. Always garaged, no rust, 4-wheel drifts are fun!

With the ALDL jumpered in diagnostic mode and the IAC connected, key ON, do you hear the IAC clicking (vibrates a bit too)? If not, disconnect the electrical connector, then unscrew the IAC, then turn the key ON. Now while holding the pintle from shooting out plug the IAC connector back in. You should feel the pintle moving under your finger and hear it clicking and feel the IAC vibrate. If it still does not work then it's probably dead. This is assuming the wiring is intact.

quote Originally posted by Hudini: With the ALDL jumpered in diagnostic mode and the IAC connected, key ON, do you hear the IAC clicking (vibrates a bit too)?

i can hear the IAC vibrating now - this is after i took it out and cleaned it - dunno if that helped or not. i took it out yesterday in 32C weather and ran it hard, then tried to stall going slow in residential areas, but it ran like a champ. perhaps this fixed it. but one question - i cant find anyplace where my throttlebody has a brass plate. where do i look for this to check if my throttlebody has been tampered with?

thanks
jon

anyone?
thanks
jon

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I'm the original owner of a white ' 84 2M4 purchased Dec 10, 1983 from Pontiac. Always garaged, no rust, 4-wheel drifts are fun!

well, my car has been running like a champ for the last few months, but yesterday i suddenly died after coming off the freeway onto the exit ramp. (of course it always happens at a stop light with lots of cars behind me and everybody mad that im blocking the way - certainly i would be mad if i were them....) since i cleaned it and it worked for a while, even tho it failed the chicken mcnizzle test, perhaps i should just clean it again, but still the question in my mind - HOW CAN I TELL IF THE BUTTERFLY HAS BEEN TAMPERED WITH? i dont have high idle when its warm - starts at 2200, soon goes to 1800 then after a little while 1500 and finally it idles at 900. so i dont think i have a vacuum leak.
jon

...my old fart fantasy dreams Jennifer Anniston & Angilina Jolie desparately chick fight over me ,and my IAC works as good as yours !!!
..I am not sure what problem you have now,,the car died at a stop ,,is it running now ??
what does it run like.
The Number 1 test for any IAC made before 1995 is to add juice and it pops out with vigor..
If you have a duke TBI you check bottom gasket,,make sure top is secured to bottom of TBI..you will see the 2 screws
...If the Car was running good ,its doubtfull your TBI air valve is faulty
...Is the car running now ???

[This message has been edited by uhlanstan (edited 05-01-2010).]

If you run WinALDL software through the ALDL port, if seems to show readings on IAC coil A and coil B.

I think it identifies if either one is dead or non-functional. Can anyone who "knows" WinALDL confirm this??

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quote Originally posted by uhlanstan: ..I am not sure what problem you have now,,the car died at a stop ,,is it running now ?? what does it run like. The Number 1 test for any IAC made before 1995 is to add juice and it pops out with vigor.. If you have a duke TBI you check bottom gasket,,make sure top is secured to bottom of TBI..you will see the 2 screws ...If the Car was running good ,its doubtfull your TBI air valve is faulty ...Is the car running now ???

thanks uhlanstan for your concern and help.
after a stop light of cooling down (it wont start right away when it stalls hot) (and lots of frustrated drivers calling my baby a POS), my car started and i managed to drive the 1/2 mile to the soccer game. 1 hour later, after the car cooled down (it was not overheating, the coolant temperature is/was normal, and my 84 engine compartment also has the side vents from the 85-88 fieros so the temp of the engine compartment was normal too...) it started normally and ran almost to my house when it stalled at a stop light again, managed to start it right away and drove the rest of the way home, stalled in the driveway, started and is now in the garage. so yes, the car runs and runs good when the weather is cold or normal but it was a little warm that day and it stalled again getting off the highway.

since my car failed the chicken mcnizzle test i figure that it must either be an air leak somewhere in the fuel injection system, or the TBI. the TBI pintle looks worn - not pitted, but shiny on one side, i checked the PCV valve and it rattles as the haynes manual says it should, BUT the hose is (was) loose on the shaft, so i installed a steel hose clamp. now its not loose. the haynes manual says that stalling can be caused by a clogged PCV filter, and my filter is dripping with oil, so i took a needle nose pliers and pulled the filter out of the housing to allow free breathing from the valve cover assembly. can i run it without a filter or should i get another one? no smog checks here, but this car is originally from california.

i torqued the TBI screws to 145 inch pounds - they were a little loose. tomorrow i will use a hose as the haynes manual says to listen for leaks in the TBI. how do i check the bottom gasket? do i remove the two screws and remove the TBI from the intake manifold? how will i know if i have a good gasket? what do you mean by testing the TBI by adding juice?
thanks again
jon

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I'm the original owner of a white ' 84 2M4 purchased Dec 10, 1983 from Pontiac. Always garaged, no rust, 4-wheel drifts are fun!

quote Originally posted by fierosound: If you run WinALDL software through the ALDL port, if seems to show readings on IAC coil A and coil B. I think it identifies if either one is dead or non-functional. Can anyone who "knows" WinALDL confirm this??

i have been tempted to buy an older laptop and get WinALDL software, but im afraid that i will just waste my money given my computer skills. if you think i have trouble with my car, you should see me with a computer
jon

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I'm the original owner of a white ' 84 2M4 purchased Dec 10, 1983 from Pontiac. Always garaged, no rust, 4-wheel drifts are fun!

Sounds like your ignition module is on it's way out. Dies when hot but restarts when cool. If this is the problem then one day it won't restart when cool. You can have it tested for free at the chain stores like Advance, Autozone, etc. You have those in Quebec?

I would replace the little mesh filter in the air cleaner. Burning oil has the effect of lowering the gasoline's octane and the Duke is susceptible to knock under load anyway. It also does not cost much. If liquid oil is being forced into the air cleaner then you have another issue like a clogged cat. Oil vapor is no big deal though.

I believe Chicken McNizzle is specifically referring to the V6 throttle body when talking about the butterfly being tampered with. Your '84 should not have that issue especially since you are the original owner and have never messed with your TBI adjustments.

Under the TBI bottom gasket there is a small passage that has been known to clog over the years. This causes various rough running issues. Replacement gaskets are available as well as a rebuild kit from Autozone for $33 US. If yours is original then maybe it's time to take a look?