Cleaning your Idle Air Control (IAC) Valve

[MTL_4runner]

I figured I would start a thread on this subject since cleaning my own had caused me some minor headaches in getting my 4runner back up and on the road quickly. The IAC (idle air control) valve is basically what controls the idle speed on modern fuel injected motors. Gone are the days of just turning up the "idle screw" if your engine is idling a bit low. So critical to having a good idle quality is to make sure you keep both the throttle body (TB) and the IAC clean. I've attached a few different types of TBs for different engines to make sure I cover the different models available in the 96-04 Tacomas and 96-02 4runners.

[Seanz0rz]

cleaned out mine, runs significantly better at idle!

cant wait for the writeup to see if i did it properly!

[wizzells]

I noticed after cleaning my throttle body, installing a True Flow intake and filter, yanking the airbox elbow out, and pulling the EFI fuse, that my idle was hanging up when the engine was warm. It was sitting between 1000-1100 at first. It slowly started to creep down after that and took about 50 miles of driving before returning to normal - 700 RPM or so when hot. I figure this is probably due to the cleaning and the EFI reset that was performed and shouldn't be anything to worry about.

[MTL_4runner]

I'll go through the steps for an IAC on a 96-02 5VZ motor (which will be very similar to a 3RZ and 2RZ IAC), but the 02 and up 5VZ and other motors like the 1GR-FE , 1UZ-FE and 2UZ-FE will differ considerably since they use a throttle-by-wire system than also integrates the IAC valve within the assembly. If someone comes up with a good writeup for those later, feel free to add it to this thread.

Steps:

1) The first thing you need to do is to remove the intake tube to give you access to the throttle body itself.

2) Next you'll need to remove the throttle body from the intake. There are 2 coolant hoses, an IAC air supply hose, the connector for the TPS & IAC and finally the 4 bolts holding the throttle body to the intake.

3) You need to remove the IAC valve from the throttle body. There are 4 screws (see pic below) which attach the IAC and you need to be very careful not to strip these out. If you do, you can drill the heads off the screws, remove the IAC valve and then use pliers or vice-grips to remove the remainder of each screw. Obviously you'll need to get new screws from the dealer in such a circumstance.

4) You'll want to remove the electric solenoid portion of the valve (see pic below). You do this by picking out the RTV on the screw heads and then removing the 2 screws holding the solenoid body (ie the light green part) to the IAC body.

5) Now you're finally ready to clean the IAC valve itself. You'll want to spray carb or intake cleaner into the metering holes of the IAC (see pic below). You'll then want to rotate the valve by turing the shaft of the solenoid (ie the part which would have protruded into the light green solenoid portion you removed in the previous step). If the carbon buildup is heavy you may need to let this sit longer or use a small toothbrush, Q-Tip or other instrument to aid in the cleaning process.

6) Once the valve is clean and rototates freely, you should liberally spray in a light oil lubricant like PB blaster, WD40 or similar and let that sit for at least an hour. Once you've done that, dump out any excess.

7) You can skip this step but I think this is critical to ensure you have a well functioning IAC to reinstall. The best way to do this is to use a 12V battery (I actually comadeered the one out of my son's electric car for bench testing) and hook it up to make sure the valve was opening and closing properly per the FSM (see attached pic below). If it is still stuck or doesn't respond, the valve is either still sticking (in which case return to step 5 or the solenoid is bad and you'll need to replace the part).

8) At this point you should now be ready to reinstall the IAC valve. The install is obvously the reverse of the install but be sure to add a tiny bit of RTV to the mating surface of the solenoid (light green part) before you reinstall the 2 screws again, but be sure not to add enough that any might fall inside or get stuck to the rotating portion of the valve. Failure to RTV can create air leaks which can aggravate a poor idle situation. Then you should add more RTV to the 2 screws attaching the solenoid to the valve body. The rubber IAC and metal throttle body gaskets can be reused, but if there is any question of sealing, a new one can be purchased at the dealer fairly inexpensively. If you live in a rust belt, I also suggest adding RTV to the 4 screws which attach the IAC valve to the throttle body.

9) Start the truck again and allow it to come up to temperature. The truck should slowly start learning the new setting and the idle should return right where it should have (about 700-750 RPM). After about 1 hour of driving the engine should be smooth again but may take longer depending on the environmental conditions.

If the truck's idle is still high when you reinstall everything, don't panic, it may need time to relearn the idle setting again. If you find that you continue to have problems with your IAC valve you can always get a new IAC if yours isn't going back to normal after a few days. Anyone that's interested, the P/N is 22270-62050 and they're about $230 new from the dealer.