MattNuge

I just swapped the motor in my 98 4Runner with a 99 motor (3.4L V6). I ran into an issue with high idle. After getting some advice and doing some research, I decided to clean my IAC valve, boy what a difference. The valve was smothered in carbon build up, not allow the solenoid to operate properly. With about 30 minutes of effort, the new motor purrs like a kitten (almost like brand new). Here's the write up, probably well worth doing on a periodic basis. Please add anything that you think I missed.

1) Disconnect and label throttle cables.

2) Remove air intake tube to access 4 throttle body bolts.

3) Unbolt the 4 bolts holding the throttle body to the intake.

4) Label and remove hoses connected to the IAC. There should be 3, 2 coolant hoses and 1 air supply to the IAC. (Putting a shop rag under the throttle body might help the mess since you'll get a little coolant spillage). There will also be 2 electrical plugs you need to remove.

5) As you remove the throttle body from the intake, examine the gasket between the throttle body and the intake, may need to be replaced.

6) There are 4 screws holding the IAC valve to the throttle body (IAC valve has a light green solenoid on it). Unscrew the screws, being carefully not the strip the screws (they're on a bit tight, I stripped one but a pair of vice grips worked out nice).

7) Remove electric solenoid from IAC valve (light green part) by scraping and picking out the RTV from the 2 screws attaching the solenoid.

8) Now clean the IAC valve. Spray carb or intake cleaner into the holes, removing as much carbon build up as you can. You should also rotate the valve by turning the shaft on the solenoid. If you have heavy build up, let the carb/intake cleaner sit a little and use a Q-tip.

9) Once clean, liberally spray a lubricant onto the valve, allowing it to rotate freely. (I just used WD-40)

10) Reinstall all parts in reverse order. You should add a little bit of RTV to the surface of the solenoid to the throttle body to prevent air leakage. As well, you should RTV the screws attaching the solenoid to the throttle body.

11) Your motor should run like a charm now. Start the motor and let the motor warm up. FYI, it may take a little extra time for your motor to adjust to the new idle. After driving for about 30 minutes, my motor was as good as new.