Surging idle on cold EJ22 - any ideas?

silverbullet · Initiate Jedi Joined: 03 Sep 2009 Posts: 25

Without digging up some very old posts and red herring faults - and to cut to the chase - my early EJ22 (c.1990, brown label plastic maf and fault lamp inside ecu) had always suffered from a fast idle that would creep upwards to c.1300 when hot, occasionally dropping back and going lumpy at 800 rpm. Very odd.
I recently fitted an RJES VSS as the loom had a tail for it - you can guess who the original "convertors" may have been - but the idle persisted in being high, a good 1100 rpm when cold.
Emissions were always within limits for a 1990 T3 bus at MOT.
The AT/MT wire has now been earthed, it dropped the idle by about 50 rpm.
The throttle body stop clearance has been checked to factory data and the 4-wire pot checked for correct idle position and switching, so in desperation I loosened the two screws on the ISCV and backed it off to get the idle down to ~850 which is acceptable.
But...now when cold, if the throttle is blipped e.g right after starting to drop it off of the fast idle, the rpm seems to dip and bounce like a worn-out damper a couple of times before settling

Have I done the wrong thing or has anyone ever experienced this fault?
Engine has RJES exhaust, no inlet or breather system air leaks (it did have a split crankcase hose in the past) and currently has a nasty cheapo cone filter.

Help!

Joel · Posted: Fri Sep 21, 2012 4:34 am Post subject:

Have you tried cleaning out the IACV?

they gum up with crap over the years and the bouncy idle is exactly what they do.
Mine used to do it periodically, I'm a lazy ass though and just spray the Subaru upper engine cleaner down the hose rather than pull the valve off and clean it properly but heres a great thread on nasioc about it

http://forums.nasioc.com/forums/showthread.php?t=781242

That's the later style but the idea is the same.
_________________
1974 1303 Germanlook Suba-Beetle
Subaru EJ254, BoostR 17", 4 Wheel discs, Topline suspension and A/C

silverbullet · Initiate Jedi Joined: 03 Sep 2009 Posts: 25

Thanks. The ISCV is clean as a whistle. (This one has the putty-coloured stepper motor mounted vertically, below and to the left of the throttle body)
I lifted the stepper motor off to check for magnetic particles or contamination and to remove corrosion in the manifold counterbore that was preventing the motor from being adjusted.
A gentle scrape and a smear of silicone grease did the job.

I can rotate the valve spindle by using the magnetic flux from a small screwdriver, so definitely isn't stuck or gummed up!

Could it be that I need to drive the bus for good distance so that the ecu can "re-learn" after all the changes? I have been told by an experienced Impreza tuner that the ecu's can take a while to settle down, sometimes an hour's driving in varied conditions is necessary.

PS No fault codes other than purge valve.

Joel · Posted: Fri Sep 21, 2012 11:38 pm Post subject:

It would pay to get some miles on it first to see if it sorts itself out if you're confident all is well with the IACV.

Mine once or twice now has done similar if I've had the engine out for a few weeks or no power to the ECU.

The idle wouldl hunt up and down by about 500rpm at times usually only when hot though.
I used to give it a shot of the subi upper engine cleaner down the hose but it may have just stopped the hunting of it's own accord once the ECU got its bearings back.
_________________
1974 1303 Germanlook Suba-Beetle
Subaru EJ254, BoostR 17", 4 Wheel discs, Topline suspension and A/C

silverbullet · Initiate Jedi Joined: 03 Sep 2009 Posts: 25

Maybe I'll disconnect the battery for 48 hrs to let the ecu re-set, then go out for a good drive. Was hoping to get it settled before the autumn set in here, but the late summer has rapidly gone downhill. Might have to garage it until the spring at this rate Sad

leadfootmik · Wannabe Joined: 29 Jun 2012 Posts: 2

had very similar to this with my ej22.early one like yours also by i guess tsr?.
the cure was an unhappy MAF due to a cone filter with no real protection from moisture ingress.

idle from cold was low,when warm would hunt up and down and sometimes it would even stall when slowing down.

silverbullet · Initiate Jedi Joined: 03 Sep 2009 Posts: 25

Thanks for that info. Funnily enough I had to move it the other day (road test still pending) and with the change in weather here in the UK, preventing it from stalling was a real challenge.
Before I adjusted the ISCV it was never a problem, but it has always had the crappy cone filter.
There must be condensation on the MAF sensor; that cone is going in the bin tonight!
I have a big cylinder filter housing from an old Rover SD1 Vitesse V8, that'll be big enough and I can connect the VW (diesel) intake pipe to keep it quiet Happy