Is there a way to test the IAC???

[turbo39151]

My IAC counts are through the roof! 60's- 70's. My local tuning expert has his T tuned in the 20-30 range as it should be. Mine will only drop in low 50's. I killed the battery power to rest the ecu and IAC motor and when we started it up the numbers dropped to 38-39. Still won't hold still though... started climbing.

btw, IAC has been removed, cleaned and reinstalled properly.

Any ideas?

 

[441120]

Iac

Check to see if there is any carbon on the throttle plates, try cleaning them, as the film builds up the IAC has to compensate to maintain idle.
If everything OK try resetting minimum idle.
1. Ground ALDL for 15 sec
2.unplug IAC
3.set idle speed
4.set TPS
5.reconnect IAC

 

[Squid4life]

To get mine right I had to adjust the IAC, then the TPS, then the IAC, then the TPS, etc. :smile:

 

[VadersV6]

441120 has it right, although I forget which 2 pins have to be shorted. Who here remembers? I wanna say the top right and top left pins? ..You short those pins, which pushes the IAC pintle forward and seals it so that when you start adjusting the idle set screw, you wont have any extra air coming in, screwing everything up. You short those pins with a paper clip for 30 seconds, then turn ignition off and pull the paper clip out. Disconnect the IAC connector. Try to start the car. If it wont start, open the throttle blade a little bit by turning the idle set screw. Keep doing that until the motor will start. The engine should be warmed up before you start this. Now with the engine idling, start turning the idle set screw until the engine just barely dies. It should be able to idle at 400-500rpm without the IAC plugged in, but it doesnt matter. Now that the engine died, turn off the ignition and plug the IAC connector back in. Now you're good. Now its time to adjust the TPS. Make sure you are no higher than .44 volts at idle. Dont go back and forth between IAC-TPS-IAC-TPS. Thats pointless. The throttle position was set when you set the IAC, and it should be left alone.
This is the way I did it and my IAC counts are like 10-15. I think the counts were about 70 or something when I bought the car.

 

[strikeeagle]

Increase minimum air.

The ECM is commanding higher IAC counts because there is insufficient air flow around the throttle blade and into the engine to maintain proper idle.

Do not increase minimum air past the point where the chip no longer controls idle RPM - a no-no.

Keep idle TPS in range while you're doing this by adjusting TPS as necessary.

If this doesn't work you have a "maintenance" issue.

strike

 

[turbojd]

You short pins A and B top right for IAC re-set

 

[VadersV6]

You short pins A and B top right for IAC re-set

Is pin A the top left pin? Was I right?

 

[carrddine]

if you disconnect the battery should it reset it self,just curious....

 

[turbo39151]

according to some of my paperwork, the A & B terminals are located as follows:

A is at the top far right as you face it.
B is immediately to the left of A on the top row.

I'll go check and see if this all works because my other TR is also giving me crazy IAC readings, high 60's -70's...


Why would all these cars be so out of tune in that area?

 

[turbo39151]

I tried this reset trick and it doesn't work for me.

I did the jumper, waited 30 seconds, and disconnected the IAC plug. The car started right up and and ran at 1400 rpm. It dropped down in idle, and the IAC counts dropped to 00. I turned the car off, plugged the IAC back in and started the car and the counts were over 100 even with the screw adjusted all the way back till it's almost off!

I got it down to 88 but it won't go down anymore...

This is a problem for both of my TR's WTF???!?

Is there no way to check it? Or do I just buy new ones?

 

[strikeeagle]

Did you read my post?

Explain something. Why wouldn't the ECM command MORE IAC when you CLOSE the throttle blade by BACKING OUT the minimum air screw?

strike

 

[turbo39151]

SO, what you're saying is that I have to open the throttle blade? What do I do about the crazy RPM???

 

[Squid4life]

To get mine right I had to adjust the IAC, then the TPS, then the IAC, then the TPS, etc. :smile:

My crazy idle toned down when I finally had everything adjusted.

 

[strikeeagle]

Adjust minimum air so that the screw is contacting the linkage, then just a fraction of a turn more, so that the throttle blade just begins to open. What are RPM, TPS and IAC? Now, try increasing minimum air ever so slightly. What are the new values? Car fully warmed up. In park.

strike

 

[turbo39151]

I'll work on it probably tonight or tomorrow and post back my results. I know of several TR's with this issue. Is this a common problem and is there anything else I should look at while I'm working on this issue???

 

[turbojd]

1. Key off 2. short pins A and B on ALDL 3. key on 4. wait 30 seconds 5. unplug IAC 6. key off 7. start engine 8. set idle speed to about 750 rpm 9. key off 10.reconnect IAC 11.start engine, IAC count should be with in range

 

[strikeeagle]

1. Key off 2. short pins A and B on ALDL 3. key on 4. wait 30 seconds 5. unplug IAC 6. key off 7. start engine 8. set idle speed to about 750 rpm 9. key off 10.reconnect IAC 11.start engine, IAC count should be with in range

Unless something is fubar (example - the minimum air screw is maladjusted, keeping the throttle blade too far open, or the throttle blade doesn't seal in the bore, or you have some sort of "unintended" air leak) the chip commands idle RPM.

strike

 

[turbo39151]

Ok, I finally had a chance to mess with this thing again today. I followed the procedure as outlined by turbojd. After the IAC was disconnected, the car would not start. I tried several times and them plugged the IAC back in and the car ran with a really high idle and IAC was in the 100's. Eventually it calmed down into the 60-70 range and I adjusted the screw and got it to go to 52. I tured the car off and retried it and that was as far as I could go.

I reset the TPS to .44 and it lost the setting once and then I reset it again to
.42 and it stayed and that is where my last IAC reading posted at 52.

So here's my question. If the IAC unit accepts some sort of calibration it should be in working order, correct? If it is, then what else should I be looking at in order to correct this issue? Bad TPS?, ???

BTW, just running an emissions chip right now. WIll this chip interfere with the IAC? I've been told that it shouldn't

The car runs fine otherwise...

 

[VadersV6]

You did it all wrong.
First, unscrew and remove the IAC motor (ignition off) and clean the pintle, and also clean the pintle seat and holes in the throttle body. (the conical hole that the IAC pintle seals in). Use carb cleaner and wipe the pintle seat clean with a paper towel. Screw it back in, but dont over-tighten it cause you can crack the sealing gasket for the IAC. (is the gasket in there????)
Warm the engine up. Shut it off.
Turn the idle air screw in a few times to open the throttle blade a little.
Ignition on, short those 2 pins (top right 2 pins) and wait. Shut ignition off. Pull that paper clip AFTER ignition is off.
Pull the IAC connector.
Start the engine. Slowly turn the idle air screw out and keep bringing the idle down until the engine dies.
Turn the ignition OFF.
Plug the IAC CONNECTOR back in.
Now turn ignition on.
Adjust the TPS sensor to .44 volts at idle. Scanmaster makes it easy.
Tighten TPS down.
Shut ignition off.
Start engine.
Good to go.

 

[turbo39151]

Ok. I'll try it again. Sorry for being a PITA but I don't know much about tuning. I turn the wrench...