'99 EJ25 Idle Adjustment

[westone]

Okay, according to my mechanic, the idle on the EJ25 in my '99 Outback is controlled by the computer, and there is no adjustment. However, after repairing a blown cylinder head gasket and having both heads machined and valves done, my '99 Outback was idling at about 600 RPM, where it had previously idled around 800rpm, and at 600 the car was shaking somewhat.

My mechanic found on Alldata.com information on how to adjust the idle on this engine, and turned it up to 1000rpm. It smoothed out, but after a day or two set a P0507 code - RPM higher than expected for condition.

It is Saturday and mechanic is having a well deserved day off. I have been unable to find any info on the net about the idle on this engine. Is anyone familiar with what it takes to move the idle on this car? I'd like to try to adjust it down to about 800 and see how it goes.

Thanks,
Bill

[porcupine73]

woah woah woah this does not sound right. There is no idle adjustment, yes it is controlled by the ECU. I don't know what he would have seen on all data to make him think that; alldata has the oem service info. However some people think it wise to adjust the idle air control valve in some manner......subaru's suggestion is if someone has done that to replace the idle air control valve. The wiser choice would have been to clean the iacv with seafoam or somethign like that; they usually get carbon build up after time nad then even when fully oepn they can't passe nough air to idle at the right rpm. The code you got means that even when the ECU closes the idle air contorl valve as far as it deems possible/practicable and the idle is still above the setpoint.

[westone]

Well I won't argue with that. But the car is running strong now, getting better MPG than it ever has, and it is no longer setting a misfire code, which it was before. Only problem is it won't pass inspection until this issue is cleared up.

[porcupine73]

Hm yah I don't know, I found an article I think the tech saw which could be misread to imply they are saying to adjust the throttle cable so that the throttle is open slightly all the time. That could definitely cause the problem you are having.

[johnson]

Originally posted by porcupine73
Hm yah I don't know, I found an article I think the tech saw which could be misread to imply they are saying to adjust the throttle cable so that the throttle is open slightly all the time. That could definitely cause the problem you are having.

That's hilarious, talk about "beating the system."

[westone]

I spoke to my mechanic yesterday, and yes he did adjust the IAC valve. Because of the P0507 code, we adjusted it again just about 1/16" back toward the original position. That has the idle running between 725 and 900rpm, depending on the conditions. When at operating temp it is usually 725 with no A/C running.

It has only been a few drive cycles so far, but no CEL yet.

[porcupine73]

Ok, I hope it works out. There is no adjustment that is supposed to be made by hoomans; the whole point of the idle air control valve is that the engine computer makes the adjustments by controlling how much the valve is open and thus how much air is let into the intake at idle.

[westone]

I'll keep you posted if any further codes are set.

The original problem was it was idling too low and setting a misfire code. When we turned the idle up, the misfire code went away. But then the 0507 code appeared. I think we have resolved, but time will tell.

[johnson]

I wonder how the mechanic is "adjusting" the IAC valve since there is no means to adjust it?

[porcupine73]

Some of them do have some screws I think but those are for calibration when manufacturered and aren't supposed to be touched after that. My guess is the IACV is all coked and carboned up and can't pass enough air even when fully open to allow idling and maybe the tech has adjusted the throttle or cruise cable to hold the throttle open slightly at idle.

ref1: http://endwrench.com/images/pdfs/LegNoTurboSum04.pdf
These valves are pre-set. Never try to adjust them in attempt to repair a vehicle. If you find yourself working on a driveability concern and this valve shows signs of tampering, the valve must be replaced. There are no procedures to return it to the factory settings.

ref2: http://endwrench.com/images/pdfs/DTCInfo.pdf