94 3.0 intermittent high idle

[kuene]

94, manual, 3.0, 4x4.


I've had an intermittent (around half the time) high idle (1500-200) for the last year that I've owned this truck. I've cleaned the IAC, it looks good. Can't find any obvious leaks, but haven't looked hard yet. My logic could be flawed, but it would seem like a leak would cause it to always idle high, and this happens/doesn't happen randomly. I notice that when I'm experiencing a high idle, and I temporarily unplug the harness to IAC, the idle returns to normal. First thought I had was to replace the IAC. However, I've also seen a thread or two on here stating that a bad alternator with improper voltage will cause the computer to increase the revs. Before I start replacing things - anybody have an idea if my particular symptoms are more like a bad IAC, bad PCV, a vacuum leak, a bad alternator, or something else entirely? Any suggestion on what else to to check for before diagnosis? Thank you.

 

[superj]

is there any instructions on what the resistance should be on the iac to see if its good?

 

[kuene]

That's a good question - i don't know but will google. I suppose would be easy to test with multimeter across the connector.