Sadgrandad

93 WRX

1) Can anyone explain (as if to Mickey Mouse) how the idle air solenoid works and what its function is, please?

2) When I take the cap off mine, the spindle/plunger thing can only be turned through about 90 degrees and lifted or depressed a few mm, is this normal?

3) I keep getting an intermittent e/c 23 (i.a. solenoid) but it often only lights for a few seconds and seems to go off when I depress the clutch. The light does not seem related to any immediate change in performance. If there is a fault, should the light stay on or should it come on next time the car is started?

Pleeeeeeeeeeeeeeeeeease heeeeeeeeeeeeelp!

Jolly Green Monster

iTrader: (4)

I can only help with the CEL..

It will come on when it detects a fault and store it in the memory.. if the fault goes away it will switch off the light but keep it in the history..

That is my experiance of it anyway..

Touch wood not had a problem with idle controller..

you could just buy a secondhand one from www.gradea-subaru.co.uk

JGM

dnb

Probably needs some of the air pipes cleaning. I'm afraid you'll have to search, as I can't remember the details.

Sadgrandad

Thanks guys. Am I right in thinking that the idle air solenoid doesn't just control air for idling?
Rod

dr_ming

The idle air solenoid is a electrically operated valve that partly bypasses the throttle butterfly valve to maintain a constant idle speed (and also sometimes to provide an increased idle during warm-up, athough this may also be done by a separate valve).

For small thottle openings, it may have some effect of the normal engine running, but not much. This depends on the control strategy. To reduce wear on the valve, some systems turn off the drive to the idle air control solenoid as soon as they detect the thottle has opened. For large throttle openings, it will have no effect on engine running. Even if it were jammed open, you would see a much higher than normal idling speed, but the difference in air mass for wide throttle openings would be insignificant.

These valves usually operate with a PWM (pulse-width modulated) drive signal, operating frequency between 100Hz and 1kHz. Basically, the larger the duty cycle (on time vs. off time) the more the valve is opened. Usual faults are blocked (oily) pipes, or sticking/worn actuator (so valve is sluggish to open/close). In this instance, dissasembly and a good douse in WD40 usually helps.

The physical travel of the plunger/actuator is usually small (a few mm) - it doesn't need to let much air through to make a considerable difference to idle speed.


[Edited by dr_ming - 11/10/2003 12:34:34 PM]