Idle air senor question

[jmeti000]

I need a new one, and seem to be having an issue finding one that works. The first one I bought from autozone and the jeep idled at 2500 after putting it in. Thought "well, maybe it was just a dud", so I exchanged it and the second one came all unscrewed in the throttle body and I had to pull out the spring and screw with needle nose pliers. Took it back and put the old one in again and decided to get one from the dealer. The one from the dealer came all apart in the throttle body too, so I thought maybe it was a factory glitch or something. Fast forward a month later and living with the old one, I finally decided to give it a go again. I ordered another one, put it in and it idled beautifully. Drove about a mile down the road and all of a sudden its idleing at 1500, so I pull over and pull it out only to find once again the sensor came all apart on me.

Anyone else have this issue? I cant believe that even the dealer one did the same thing...am I missing a trick to installing it? Or am I just having really REALLY bad luck with these things?

 

[Laurent Wagoneer]

Have you cleaned out the whole throttle body? It may be dirty this causing it to stick.

 

[jmeti000]

Throttle body is clean. Even if it was dirty I cant imagine that would cause 3 entirely new sensors to come apart. I was beginning to think there was something wrong with the TB itself, except why then does the old one not do the same thing?

 

[8Mud]

What year and motor?

 

[jmeti000]

Its and 87 4.0. Sorry, forgot that part.

 

[8Mud]

Most likely you aren't getting the IAC housing in all the way. It has an "O" ring gasket, you have to coat the "O" ring with oil, push the IAC housing in all the way to the "O" ring, then wiggle it a little left and right to get the "O" ring to slip in. The housing fits tight against the TB housing flush, with no gap between the IAC housing and the mount. If you just push the IAC housing up to the "O" ring without getting it all the way in, you may just be crushing it while tightening the bolts and the IAC housing will never fit flush. This may be your issue. But I seem to remember a lot of extra length on the IAC piston rod, I don't know exactly how it is popping out of there, just some guesses.

The only other reasons I can think of for trouble are, the piston for the IAC is out too far from the factory and you are bending or destroying the piston rod (the threaded drive rod for the piston) trying to force it in there. Or I guess if all else is as it should be, the brass seat for the IAC piston in the TB has fallen out. I've never seen the seat fall out, but my guess is anything is possible.

Most times the IAC itself isn't the issue anyway. A little oil sprayed behind the piston so it runs down into the piston drive rod and the drive motor usually loosens things up and it works fine. The grease gets thick with grit and old age inside the tiny drive motor and rod assembly. Or you have a battery or charging issue. The IAC seems to be voltage sensitive and is one of the first things to act up with low voltage.

I clean up the IAC seat inside the TB with something plastic, clean off the rubber stopper/piston and let a little synthetic oil run behind the piston. I still have my original 1987 IAC, though it has acted up on occasion from dirt, grit, too thick lubrication or low voltage.

Careful moving that piston around, the drive rod for the piston is tiny and so are the gears in the drive motor. If you hook up the IAC to the connector with the key in the run position and the IAC is out of the TB, it will launch the piston and the spring.

 

[joe_peters]

I'm with 8Mud. That IAC should not be able to physically over-extend itself and fall apart if installed correctly.