Air Idle Control Valve EJ25 SOHC

[stubbie]

My AICV seems to be playing up and seems to be slow to operate. My ECU is showing two fault codes one for the Vehicle speed sensor and one for the AICV.
The symptoms im getting are -
1) That the engine will occasionally continue to rev for a period after I have taken my foot off the accelerator to change gear.
2) The engine will occasionally stall when I take my foot off the accelerator / when I have stopped, normally when engine is warm.
3) The engine overrevs on starting (most recent problem)
4) On one occasion the engine sounded like it was only running on 3 cylinders when idling, but this seems to have sorted itself out and has not happened since.

On the basis of the above I have ordered a second hand unit from the states (part number A33661R02) after my local subaru dealer quoted £419.56 for a replacement!!

I have removed the existing AICV to give it a clean, but everything looked to be fine. I have reset the ECU overnight by disconnecting the battery but on start up the AICV fault along with vehicle speed sensor fault code reappears.

The AICV appears to be a simple solenoid that is driven in or out to stem air flow, but I have read that these are factory set, is this true??? what does the ECU measure to determine ACV position?

Are there any other problems that could be causing the above faults.

Where can I locate a factory manual that covers the 1999 EJ25 sohc engine?

[big red bus]

Would have said you need to sort out a vehicle speed signal first. Do you have a speed sensor giving the ecu a reading . This vehicle speed sensor gives lots of silly problems like this and on a later engine like you have I think you need to sort that out. You may well find that this cures the other prob as well. Rjes does speed sensors that fit where the orig cruise control on the back of the dash.

[stubbie]

Thanks big red bus,
The RJES speed sensor is fitted behind the dash, I'm not sure where this plugs into the ECU as I didnt install it.
Like you said I was told that the engine wouldnt run properly without the sensor fitted. I seem also to remember seeing it posted somwhere that the vehicle speed signal fault was pretty much a standing alarm even if the RJES sensor had been fitted?
Have posted the same problem on the RJES forum but no replies there.

[syncroandy]

Hi Stubbie, I had similar behaviour with mine, which reduced noticeably after I refitted the PAS pump. I had been considering removing and cleaning the IAC, but I'll not bother now. I'm sure its worth a go though.

I don't see how the VSS could be involved, as the high revs at idle is at 0mph. My RJ VSS sender went pop, and it made no difference to the motor. Runs fine without IME.

[silverbullet]

Your symptoms are similar to the problems that my early EJ22 sohc is giving. I'm not getting the over-revving with a closed throttle (like your gear changes) but have had it sounding like it's only on 3. The idle creeps up when hot to about 1300.
Mine was installed by previous owner so I still don't quite know what I've got or how well it was done (not very) but...
it wasn't installed with an O2 (lambda) sensor fitted. Just bought one today and will let you know if it fixes anything.
I too looked at the IACV and sprayed it etc. made no difference - DON'T seperate the stepper motor from the valve body without scribing round it first! The "duty cycle" is factory set at manufacture.
Check for split breather or purge hoses - I had the main one on top of the crankcase split that only opened up when hot and gave a code 49. Took ages to find.

[jamesc76]

On mine i had a funny running problem which turned out to be a a spark plug sailing every know and again!! Might be worth changing them out ?

[stubbie]

The AICV arrived and has been fitted, I took it for a spin and everything is sounding and running a lot better, no over revving during start up or whilst changing gear. I will reset ECU overnight and see how it goes.

[stubbie]

Overreving bewteen gear changes has come back to haunt me, so new IACV did not fix problem, I have fitted a new RJES VSS and this seems to make the problem worse. I'm going to reset the ECU to see if the new VSS still brings up a fault code.

[stubbie]

Reset ECU overnight and have taken new VSS for a test drive, the over revving symptoms are still there, however when I checked the ECU afterwards the fault light was clear, no VSS fault and no IACV fault... so what is the cause of the over revving?

[stubbie]

The AICV arrived and has been fitted, I took it for a spin and everything is sounding and running a lot better, no over revving during start up or whilst changing gear. I will reset ECU overnight and see how it goes.

Please note that the over revving symptoms came back after I had taken the van for an extended (20 mile) test drive, it's amost like the throttle is being held open for a period of time after I let the throttle up to change gear. The cable is completely free so it's not mechanical.....

[silverbullet]

Appreciate this may not be super helpful, but have you bounced it off rjes on the vwkd forum. It's his baby and views it more than here or the brickyard.

[Jon Bisson GSY]

Hi,
I have been having a slow dance with a AICV fault for a year or so. I tried cleaning it to no avail and as the other regular fault I get is the Lambda senser I don't get more than mildly annoyed by the red light on the dash. One day I will get a new valve (where did you get yours from) and a lambda sensor (any suggestions?)
One thing I did do is make friends with my local scooby dealer and had him stick the diagnostic on the loom. Interestingly he could adjust the tickover (a bit) and also do a full clean down of all errors, as he said the ECU will hold old errors even if you disconnect it overnight.
Jon

[Pepperami]

I bought my Lambda sensor off of ebay. Can't remember the name of the company though.

[stubbie]

Hi Jon,
I purchased the AICV off ebay, from an American parts dealer dealer, search for legacy AICV and one should pop up.

[silverbullet]

Appreciate that this is getting a bit old but here goes...

BEAL (UK) LTD workshop supplies in Church St, Morley, Leeds 0113 253 8888 ring for a catalogue, good old-fashioned mail order.
Lambda sensor 2 wire £9.75!!! You won't get cheaper and the quality's good.

Does anyone know the procedure for clearing the Subaru ecu's memory of old fault codes? There's supposed to be a "join 2 wires together" method but no-one's telling...
Can't work it out from the info I've got (Downloaded manual from torrent site) as it's a dealer service book. rjes was "non-commital" about it last time I asked