legacycentral bbs

From all the reading i have done, it seems that in order to adjust the idle you need to turn the solenoid on top of the IAC and NOT the throttle stop screw on the throttle body. On my '91 EJ22 (installed in a VW camper) the IAC solenoid has only one possible position. In other words, there are no slots for the two screws (that hold the solenoid to the valve) to allow the repositioning of the solenoid on top of the IAC.

How do you adjust the idle with out these slots AND NOT TOUCH THE THROTTLE STOP SCREW?????

Many thanks for the help.

You shouldn't have to adjust it. Did you clean the valve? There should be a few-year-old thread or two on it. I can't remember the procedure myself as I haven't done it in years, but I think you just take it apart and blast it with some carb cleaner.

Check for vacuum leaks (if you haven't already) as well. They cause idle problems more often than anything IMO.

Actually I should have mentioned that I was originally trying to fix a cyclical idle problem by shooting carb cleaner in the intake of the IAC. I did remove the solenoid part of the IAC to actuate the shaft up and down while I blasted its innards.

The engine is recently rebuilt and all vacuum hoses are brand new, so vacuum leaks are most likely not the problem.

If the idle is indeed unadjustable and fully controlled by the ECU, will it learn to idle as I drive it more?

It might. As long as everything is in good shape, it should, but as with anything, there's no guarantee. Does it die or is it idling really high or is it just hunting, but drivable?

evolutionmovement wrote:It might. As long as everything is in good shape, it should, but as with anything, there's no guarantee. Does it die or is it idling really high or is it just hunting, but drivable?

It idles smoothly at 1000-1125rpms and is quite drivable now that the cyclical idle is gone.

FYI - For some reason, when I was cleaning the IAC, I did slightly stretch the spring (between the solenoid and IAC housing) that pushes the solenoid plunger back up into the solenoid. Maybe this has caused the higher idle? Why I did this, I have no idea.

Does your TB have a bypass adjustment screw on the top of it?

http://main.experiencetherave.com/subaru/images/TB/

If it does, you may want to adjust that.

Also, the IAC valve for the MT motor isn't as good as the IAC valve for the AT motors, so as you mentioned, something may have been stretched when you took it apart.

Legacy777 wrote:Does your TB have a bypass adjustment screw on the top of it?

http://main.experiencetherave.com/subaru/images/TB/

If it does, you may want to adjust that.

Also, the IAC valve for the MT motor isn't as good as the IAC valve for the AT motors, so as you mentioned, something may have been stretched when you took it apart.

There is a place for the screw, but no screw. By the looks of it, it "casted" shut at the bottom.

Rhinoculips wrote:

Legacy777 wrote:Does your TB have a bypass adjustment screw on the top of it?

http://main.experiencetherave.com/subaru/images/TB/

If it does, you may want to adjust that.

Also, the IAC valve for the MT motor isn't as good as the IAC valve for the AT motors, so as you mentioned, something may have been stretched when you took it apart.

There is a place for the screw, but no screw. By the looks of it, it "casted" shut at the bottom.

Ok, just checking. I fought a high idle problem because I cleaned the TB, and that adjustment screw was set a certain way.

Also, the IAC valve for the MT motor isn't as good as the IAC valve for the AT motors

Interesting.What is the difference?

The IAC valve on the MT ECU's only have one PWM signal sent to the IAC valve to I believe close it. There's a spring in there to cause it to open.

On the AT cars there are two PWM signals sent to the IAC valve. One to open the valve, one to close. This provides more precise control of the IAC valve and air entering the engine.

Legacy777 wrote:The IAC valve on the MT ECU's only have one PWM signal sent to the IAC valve to I believe close it. There's a spring in there to cause it to open.

On the AT cars there are two PWM signals sent to the IAC valve. One to open the valve, one to close. This provides more precise control of the IAC valve and air entering the engine.

Can a IAC valve from an automatic be used in a manual? The wiring harness has three wires with female connectors going to the IAC, BUT the solenoid on the IAC only has TWO male blades. Why would there be three wires going to the IAC and the IAC solenoid appears to only need two??????

my 92 na mt has a 3 wire iac. no spring. and adjustment slots. currently dead center.

I'm pretty sure I read in the haynes book that you should never have to adjust the idle because it's all controlled by the ECU.

Rhinoculips wrote:Can a IAC valve from an automatic be used in a manual? The wiring harness has three wires with female connectors going to the IAC, BUT the solenoid on the IAC only has TWO male blades. Why would there be three wires going to the IAC and the IAC solenoid appears to only need two??????

Depends on the ECU. The three wire IAC valves were used on the JECS ECU's. The 90-91 MT's used Hitachi ECU's, and I'm 99% sure you can't use the three wire IAC valve with them.

The three wire and two wire are completely different designs. One is a rotary design (3-wire) and one is a blade design with spring return.