IAC ohms good, but could it be bad?

[ProwlerGT]

Can anyone confirm that they've ohmed their IAC and it shows good, but ended up still being the culprit in idle/sputter/hesitation problems?

How about did the bad IAC ruin the ECU?

How about did the unknown bad ECU from bad IAC 1 ruin IAC 2 after installed?

I have a new IAC and having idling issues and I'm just exploring some out of the box thoughts, especially whether or not the IAC can be bad if the connections ohm out to spec.

[DBLerman]

My IAC was bad and the ohms were in spec. My ECU was good too. Replaced the IAC and problem was fixed...I put the old IAC back on just to make sure it was the problem and the car stalled again...New one is currently on and no problems

[ProwlerGT]

Well then I guess what would be nice to know besides just stalling the car is what is another way to test the IAC that would show its bad besides OHMing it? Is stalling the car the only other way? Anyone know?

[skunkworks]

take it apart and see if the pinicle moves in and out smoothly when spinning the rotor(maganet).

sam

[3Sfever]

The IAC (ISC) on mine passes the ohms test, and spins freely, but still does not seem to function.

My history:
- started getting intermittent crazy things happening, including idle issues
- replaced ECU caps and problem went away
- several weeks later started having consistent idle problem
(idle way too fast, and while coasting to stop, it would surge)
- Took the IAC off, tested and cleaned it, no improvement
- Took IAC off, spun the pintle fully extended, hooked harness up, turned on ignition, the pintle would not move. (I read that it should retract in that circumstance)
- I then disconnected the harness, and put IAC back on the throttlebody, (I left the harness off because I do not want it to open one day, get stuck open, causing the fast idle again.) Actually mine runs pretty good with the IAC permanently shut. Of course the ECU has no way to let in a little extra air when it needs to. like with A/C running etc.

I plan to replace it someday. Have not had the time (or weather)to fool with it recently.

Related to original questions --> could bad IAC take out the ECU (or ECU take out IAC)? . . . not sure . . . but both of mine started acting up at the same time.

[Linebckr49]

Originally Posted by 3Sfever

The IAC (ISC) on mine passes the ohms test, and spins freely, but still does not seem to function.

FYI, the pintle should NOT spin/rotate at all. it only retracts and extends, and it should be very difficult to push it in manually.

http://www.dsmisc.com/dsmweb-dw/faqs.html

Originally Posted by 3Sfever

Related to original questions --> could bad IAC take out the ECU (or ECU take out IAC)? . . . not sure . . . but both of mine started acting up at the same time.

read the above FAQ link for the ISC.

also, the ECU drivers circled in red in the pic control the ISC. you can check your ECU to determine if one of them is fried or not.

[3Sfever]

Originally Posted by Linebckr49

FYI, the pintle should NOT spin/rotate at all. it only retracts and extends, and it should be very difficult to push it in manually.

I did not explain that very clearly. I meant that I took the IAC apart and rotated the magnetic rotor, which extended the pintle.

Originally Posted by Linebckr49

http://www.dsmisc.com/dsmweb-dw/faqs.html
read the above FAQ link for the ISC.

also, the ECU drivers circled in red in the pic control the ISC. you can check your ECU to determine if one of them is fried or not.

Some good info, thanks.

[ProwlerGT]

Hey this turned out to be a productive thread ! Great new info (new to me at least) about the spinning of the magnet rotor as an alternate test. I do see my IAC active when I datalog hence why I'm reluctant to think its busted at this point since it was replaced with a reman from a good shop about 20k or less miles ago.

[3Sfever]

Note that the logger does not reflect what the IAC is actually doing, only shows what the ECU is telling it to do. (at least that is my perception). My logger showed the IAC (ISC), as acting normally, but in reality it was not moving at all.

In fact, the logger shows ISC values as changing as expected now, even with the harness disconnected.

[ProwlerGT]

Originally Posted by 3Sfever

Note that the logger does not reflect what the IAC is actually doing, only shows what the ECU is telling it to do. (at least that is my perception). My logger showed the IAC (ISC), as acting normally, but in reality it was not moving at all.

In fact, the logger shows ISC values as changing as expected now, even with the harness disconnected.

How are you sure about that though? Just curious cause I'm thinking that maybe you can't manually spin the magnet rotor fast enough to make the IAC move like it should because while I'm not an electrical expert I thought to create the magnetic field you had to spin a motor fast; as fast as a machine motor can.

If the datalogger is capturing only what the ECU tells it to do then it would seem having a datalogger isn't worth it at all if this is true for the IAC or any other part in the car. It seems like the datalogger would be reporting what the ECU receives from signals sent from all the other stuff its connected to. If the ECU were to report what its instructions are to the IAC or anything else to me this would seem like a worthless bit of info and that you could unplug the ECU from the car and simply log the ECU itself. Just speculating using my own judgement. Anybody got some comments to add on this note? Is the IAC the only device the ECU reports "what its telling it to do" for? Is this true/false? etc...