New found problem help needed

hunter4ever12 · #1 05-06-2016, 10:55 PM

So I kept getting a IAC code on my 94 k2500 with a 5.7L. So I ended up doing a reset for the sensor. I connected a jumper from terminal a to b on the diagnostic connector. I then turned the key to the on position but didn't start it. Waited 30 sec then unplugged the IAC. I then started the engine and attempted to adjust my idle. According to the procedure I read about your supposed to set the idle down to 600 rpms and then shut the engine off re plug in the sensor etc. But the problem that arises is when I try to do this literally the lowest I can get the rpms is 1600. I turn the idle screw until it damn near is out and I still can't get it any lower... So...something isn't right. Please help with a starting point at least. Thanks.

MikeCStig · #2 05-07-2016, 03:15 PM

It sounds like a possibility faulty IAC or maybe a vacuum leak somewhere else.

Schurkey · #3 05-07-2016, 06:00 PM

Quote:

Originally Posted by hunter4ever12

So I kept getting a IAC code on my 94 k2500 with a 5.7L. So I ended up doing a reset for the sensor.

The IAC is not a sensor.

Quote:

Originally Posted by hunter4ever12

I connected a jumper from terminal a to b on the diagnostic connector. I then turned the key to the on position but didn't start it. Waited 30 sec then unplugged the IAC. I then started the engine and attempted to adjust my idle. According to the procedure I read about your supposed to set the idle down to 600 rpms and then shut the engine off re plug in the sensor etc. But the problem that arises is when I try to do this literally the lowest I can get the rpms is 1600. I turn the idle screw until it damn near is out and I still can't get it any lower... So...something isn't right. Please help with a starting point at least. Thanks.

Does the IAC actually move? Maybe the thing is seized in a high-idle position.

Maybe the wire harness is broken, so the IAC never gets power to adjust the idle speed, and it's currently in a high-idle position.

hunter4ever12 · #4 05-08-2016, 12:23 AM

Quote:

Originally Posted by Schurkey

The IAC is not a sensor.

Does the IAC actually move? Maybe the thing is seized in a high-idle position.

Maybe the wire harness is broken, so the IAC never gets power to adjust the idle speed, and it's currently in a high-idle position.

I know it's not a sensor... Sorry I miss typed that... Anyway the IAC is literally brand new so I don't think it's faulty because it's doing the same thing as the old one was... Wiring harness is good and doesn't have any cracks or looks like it's been smashed or anything... Although it does appear that the previous owner did replace the plug for the IAC. It's got a new plug wired in. It appears he did it correctly by soldering the wires together then heat shrinking them(although I can't confirm that)

Schurkey · #5 05-08-2016, 01:52 AM

Quote:

Originally Posted by hunter4ever12

I know it's not a sensor... Sorry I miss typed that... Anyway the IAC is literally brand new so I don't think it's faulty because it's doing the same thing as the old one was... Wiring harness is good and doesn't have any cracks or looks like it's been smashed or anything... Although it does appear that the previous owner did replace the plug for the IAC. It's got a new plug wired in. It appears he did it correctly by soldering the wires together then heat shrinking them(although I can't confirm that)

So what happens to the idle speed when you plug the IAC passage with one of those rubber stoppers like a Thexton 368, or similar?

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