IAC solenoid failures

[bucket]

For about three years now, the IAC solenoid has crapped out every 6 months to 8 months in my '88. Normally I'd say it is just a rash of bad parts, but this is getting ridiculous. Could they be failing for another reason, like maybe an intermittent voltage spike to the solenoid? They all just plain quit working and the truck will not fast idle and it won't start without a little pedal action. However, this last one did freak out about a week before it failed. There was one evening that the truck was stuck idling at a little over 2K.

 

[89Suburban]

Wonder if your computer is taking a **** like mine is, and like I am doing right now, lol!!!!


Posted while on the porcelain throne

 

[bucket]

Wonder if your computer is taking a **** like mine is, and like I am doing right now, lol!!!!


Posted while on the porcelain throne

lol, I was wondering that too.

 

[Jims86]

I have seen a lot of IAC's replaced just because adjustments are off, and it is assumed that the solenoid has failed.
They do fail, but not that often. When you take you IAC out, does the pintle head look like it has been forced into the bore, like its trying to force itself farther than fully closed?
*has the idle screw been adjusted?
Had a guy come to me with a 1700 rpm warmed up, and the IAC was fully closed....I thought "TB Gasket".....turned out to be manifold gaskets. After they were replaced, the IAC was working just fine, but the pintle was gouged where it tried to force itself shut farther than it could go, which I guess could potentially burn it out too.
You can test it. When the engine is running, take the air claner off, and look down into, or try tistick your pinky into the idle passage(you can also feel it with a screwdriver) and with your other hand, manually open the TPS ONLY....its a little tab that the throttle crank pushes on, but it is separate. The Valve should open and close if its good.

 

[bucket]

Nope, there's never any wear on the pintle at all. When I got the truck about 7 years and 75,000 miles ago it looked like someone had just done the intake gaskets. The truck was 100% stock when I got it (except for muffler delete) and I'm assuming nobody has ever messed with the idle screw. It always idled perfect for the first 4 years and then the IAC died. Now they die all the time. The truck will always idle fine until the IAC fails again.

One thing though, I've never thought to check for play in the throttle shaft. After all these years and miles it has to have slop in it by now.

 

[Jims86]

Nope, there's never any wear on the pintle at all. When I got the truck about 7 years and 75,000 miles ago it looked like someone had just done the intake gaskets. The truck was 100% stock when I got it (except for muffler delete) and I'm assuming nobody has ever messed with the idle screw. It always idled perfect for the first 4 years and then the IAC died. Now they die all the time. The truck will always idle fine until the IAC fails again.

One thing though, I've never thought to check for play in the throttle shaft. After all these years and miles it has to have slop in it by now.

That would be a good idea...any type of air leak, will cause the IAC to close.
But if you suspect it again, do that TPS thing I posted...if you blip the TPS open, without moving the throttle blades, the IAC should jump open.

 

[bucket]

It's not a temporary thing that just happens to go away when I change the IAC. This last time I waited over a month to replace it again. The IAC was completely inactive the entire time.

 

[oneluckypops]

That would be a good idea...any type of air leak, will cause the IAC to close.
But if you suspect it again, do that TPS thing I posted...if you blip the TPS open, without moving the throttle blades, the IAC should jump open.

If ya dont mind I will add 1 more thing to your diagnostics.

If it does NOT open doing your method then dont automatically assume its a faulty IAC, You first will need to check to see if the ECM is even requesting the valve open. Plug the IAC light into the IAC plug in, If it lights then IAC is Faulty, If it does NOT light check with a scanner to see if the ECM is commanding..