Hi all. My 92 jimmy 4.3 vortec, idles fast, but smooth. Changed the IAC, and checked for leaks in the injector. I put a volt meter on the IAC leads. The four lead connector has 2 grounds and 2 hots. Both hots read a steady 12v from cold start to op. temp. I was expecting one to start out high and go down, while the other went up. Could be I'm just lost.

Here's the question. What controls the IAC? Is there a relay in line? If so, where did they hide this one?

Only had it about a month, already getting used to it.

Thank you,
Jason

when I was having a problem with my 93 Jimmy's rough idle, I started having a stiff break pedal and bad breaks. I pulled the vacuum causing a huge vacuum leak and it also had a very fast idle. So I would check to see if you have a vacuum leak somewhere.

when I was having a problem with my 93 Jimmy's rough idle, I started having a stiff break pedal and bad breaks. I pulled the vacuum causing a huge vacuum leak and it also had a very fast idle. So I would check to see if you have a vacuum leak somewhere.


go back and change your TPS (throttle position sensor) you may need a torx screwdriver T-20 easy and simple.....

Hi all. My 92 jimmy 4.3 vortec, idles fast, but smooth. Changed the IAC, and checked for leaks in the injector. I put a volt meter on the IAC leads. The four lead connector has 2 grounds and 2 hots. Both hots read a steady 12v from cold start to op. temp. I was expecting one to start out high and go down, while the other went up. Could be I'm just lost.

Here's the question. What controls the IAC? Is there a relay in line? If so, where did they hide this one?

Only had it about a month, already getting used to it.

Thank you,
Jason


check your IAC that is the motor that controls the idle with the relay for the A/C the relay may be bad......you meant the IAC and not the IAT right?

vacuum leak.

Check all vacuum lines going to and from the engine.

OK, sorry it took so long to get back. Been trying a few things. All the vacuum lines I could find are connected and in good shape. Judging by how fast the idle is, and how much it sped up when I pulled the big vac line to the brakes, it must have one BIG leak. Tried hosing things down with carb cleaner. It slowed when I soaked the upper front of the engine. Now I'm thinking it could be the gasket on the lower part of the intake, or the EGR gasket.

I'll post later and let everyone know how this works out.

I should remember, check the basics first.

Good luck, I know to check the free stuff first. Rather changing high priced sensors.

Still has to be a vacuum leak, unless you damaged your IAC valve.