Rb20 High Reving On Idle, How Do I Stop This?

[45LDE]

ok i got a rb20 that revs at 2000rpm on idle and wont come down.

Iv swaped the AAC unit over with another one still no change and adjusted the screw no change.

however if i unplug the AAC unit the revs will drop down, but in about 1min later it goes back up too 2000rpm again.

Iv checked for vac leaks and there are none.

any ideas???

Cheers

Steve.

[4drftn]

i have a very similar problem with my rb25, mine gets alot worse in cold wheather. would like to see a solution.

[Kwyjibo]

Check the IAC(Idle Air Control) valve, it is a valve that shuts as the car warms up, lets less air in and hence eventually lowers idle. One of the main ways you can see if this is the problem is if the idle doesn't lower as the engine warms up. Problem is this is based on a spring mechanism that often breaks. The IAC valve is very annoying to get to, it is in between the intake manifold, and the plenum, but I managed to get to it just by removing the crossover pipe. It is shaped like a square, with a pipe sticking out the top and bottom. I just undid the 4 screws on mine, opened it up and reattached the spring to the plate which closes up the hole.

An easy way of checking this is the problem is by blocking the hose going into it.

Someone took pictures of this in their thread but I am unable to find that now. Its an annoying job but it took heaps less time than pulling apart AFM, AAC valve and everything else that might affect idle.

Edited July 27, 2008 by Kwyjibo