I just recently purchased a 1996 Toyota T100 3.4l with a manual trans that had a high idle of about 2000 RPMs

I just bought a new IAC valve thinking it would fix the problem but it worked the same as the old one.
I tested the old IAC with a 12v battery and saw a slight opening when I closed it so I thought that must have been the problem. I use the old IAC while waiting for the new one and found that if I just took off the electromagnet motor thing that the valve must have been able to close enough because the idle dropped to about 600-800 RPMs.

I dont have any codes that directly suggest these issues but I do have a P0135 code which is for an 02 sensor.

I wasted almost a whole can of carb cleaner looking for a vacuum leak with no results.

I tried to test the TPS by unplugging it and saw no change in RPMs. I also hooked up a multimeter up and saw resistance change on it when it turned and wasn't too sure what I was supposed to see but it looks brand new.

Also I needed to replace the battery it came with with a deep cycle boat battery because I had one at my house I don't think this would be a problem but I just wanted to see.

Thank You

 

Did you try cleaning the MAF sensor and then resetting the ECU?

I guess if you've been spraying the carb cleaner near the throttle body and there were no RPM changes, I guess that would exclude the butterfly shaft sleeve bearings being out of tolerance.

 

Iv cleaned the MAF sensor by spraying carb cleaner down into the two little wires and drying it with an air compressor despite them seeming pretty clean to begin with. Is there a way to test the wires going to the IAC to see if it is being controlled correctly?

 

I don't think there is a test method to track the actual opening angle of the IAC valve. The only method I know of is the testing of the voltage being sent to the IAC.

If you have the high idle and you disconnect the IAC motor...what happens?

 

With it disconnected it drops to about 1500 which is how Iv been driving it lately. There is no check engine light with it disconnected and the idle also rises quite a bit when I turn the wheel but that is probably something the IAC would correct if it was plugged in right?

 

The idle is supposed to raise when you use the power steering. You need to check the power to the IAC, and check the resistance of the wiring too and from the IAC and the ECM. If a new IAC didn't fix the problem, you need to inspect what controls it. Also, fix the o2 sensor issue. I don't see how it could be affecting it, but you should still eliminate it as a possible cause.

 

I just test the resistance in the wires leading to the ECM and the ground and everything seem to be working. I was really hoping to find the problem there but no luck with that

 

you should do a compression test to eliminate it being a head gasket problem

 

And make sure the butterfly isn't simply sticking in the throttle body and not allowing it to close completely.

 

The truck still idles high and i am pretty sure the butterfly valve is closing enough. I realized that while im driving when i pulse the brake pedal down quick the RPMs pulse down as well. Im thinking possibly something with vacuum can cause this. Also iv been looking for the MAP ( Manifold Absolute Pressure) sensor and cant really find it.
Thank You

 

AFAIK, you'll not find a MAP Sensor since the 5vz-fe 3.4l has a MAF meter in it's stock configuration.
What leads you to look for a MAP sensor?

 

I thought MAP because I think it might be vacuum related. I just wanted to rule it out as a possiblity, guess I just did. when I usually start the truck it idles at about 1100 but rises as i drive and use the power steering

 

I too am having the exact same issues with my 97 4 runner, removed the throttle body yesterday and cleaned the IAC it was pretty gummed up seeing that I have 422000 miles on it. Cleaned the throttle body and checked to see if I could see light thru the body, I was tight. Reassembled and started the engine and it still idles at 1700. Checked for any vacuum leaks found none. Also checked to see if the linkage would make any difference when I pulled it. Nothing

 

.......

 

Its an unsolved thread sooo....

Tuneup done? Last timing belt service?

 

...........

 

Doesnt seem to be^^

Folks still come here for troubleshooting help. Maybe not for the OP. Least anyone can do is offer some direction instead of nothing.

 

I'm having the same issue, down to the same rpms. So i'd be interested in the assistance as well. And I just installed a new IAC.