legacycentral bbs

I still dont understand how cleaning it would cause a problem. I have taken a used IAC completly apart (with a dremel) before and see no reason for it to get stuck from cleaning.

I think it was coincidence and I argue that cleaning the IAC is one of the best things you could do to a high mileage engine. With my own two hands I have done 5 this way and every time there was a drastic and imidiately noticable improvement.

i know this post is VERY old, but that just justifies the point of searching for posts instead of posting new ones.
im having a few of the same problems.

ive got the 2.5 heads so my TB is upside down from what i hear (work was done by kelly). Sometimes it will idle like its about to die, other time it will idle at about 2k. when we put the plate in the the TB it started idling alot higher than normal, so we loosened the cable for the throttle... that didnt seem to do anything.. so we started loosening the screw (which i just read NOT to)... still nothing. so i guess the next thing is to try cleaning the IAC valve, if that doesnt work i will just replace it. How do i know where to set the screw at though so it is back to where its supposed to be? its turned way down atm. thanks guys

Which screw specifically are you talking about? The set stop screw on the throttle body?

There's really no adjustment procedure for that screw.....so I'm not sure what to say other then to take a guess at setting it.

ya the screw on the throttle body which i believe adjusts the idle?

That screw really is not designed to adjust the idle. That screw provides adjustment from the factory to properly calibrate the airflow past the throttle plate.

With regards the throttle body idle stop screw.... They are set in the factory, but it's not rocket science to reset it either by trial and error or by using a scan tool such as ssm or evoscan.

There is one good reason to adgust your throttle stop screw... to compensate for the loss of vacuum that is inevitable in worn motors. That loss of vacuum is incidently, in my experiance, the cause of the flooding that sometimes occurs when a subaru(or any other make of slightly worn motor) is started and moved a short distance, then floods when it is attempted to restart it.

The basic aim in adjusting the set screw is to position the IAC valve in the approximate centre of it's travel at the target idle revs.

If you can do live scans as you adjust the set screw then it is as simple as setting the iac duty cycle to about thrity-five to fourty percent while the motor is idling.

If you can't read the ecu then trial and error can be just as good on your own car if you don't mind trying things for a day or so before making the next adjustment. The aim is the same still.... to get the iac valve in the centre of it's travel at target idle revs. If you adjust the set screw too far out the iac valve has to be wide open to keep the idle going and it will be prone to cutting out if a load comes on. If the screw is too far in the iac valve will be nearly closed all the time and will be slow to pick up the revs with almost the same symptoms as having the screw too far out. Th trial is to establish which way is too far in each direction, then set it to the centre position, then, over a few start up and warming cycles fine tune the adjustmentby turning the screw a very tiny amount of a turn and testing that in all conditions.

Remember, you are not expecting the revs to change(apart from a momentary change) when you adjust the screw, you should be able to adjust it so every start up is smooth and idles is correct at all times.... within the limits of the wear in the motor, if the revs do change(permanantly) when you adjust the screw, you have gone too far or there is something else wrong.

ooo damn, so ya probably shouldnt have touched it.

Does anyone know where that coolant hose that comes off the IAC to the right side of the large hose goes to? When I was disconnecting stuff to do my HG I must of forgot to take a picture of that area now I can't figure out what line goes to it..

The side closest to the TB goes to the TB, and the other side goes into the coolant crossover piping.

yep got it finally, thanks!