cts5555

Hi guys

2000 sti 6 with Apexi Power FC installed years ago with no issues to date, left the car for a long weekend away and now the car wont idle, it drives fine and the MafV is normal ( 1200mv or so at idle and 4500mv at 1.2bar ). The car will try to idle but the revs drop very low before cutting out. If i unplug the IACV it has no effect on the idle speed. I have removed the valve and cleaned the piston, with the valve removed if i turn on the ignition the pistonj doesnt move at all where i would expect it to fully retract it will move in and out by hand but doesnt extend udner its own spring pressure? I suspect the solenoid/valve is knackered but would just like some info from a tech guy or someone who has experienced this problem before.

And, where am i likely to find a replacement?

Thanks guys

Splitpin

The ISCV on these is a stepper motor that screws the piston in and out, so it won't/shouldn't move much if you just play with it by hand. It's not like a solenoid where power pushes it one way and a spring pulls it back

Can't comment on what the Apexi ECU does (or doesn't do) when the ignition is turned on - but if it behaves in a similar manner to the OE units than it sounds odd to hear that it doesn't even twitch.

Have you tried starting the engine with the ISCV removed (but still plugged in), and something blocking the empty port on the throttle body? If the valve is still working then you should, under those circumstances, see the plunger immediately wind out as the ECU tries to reduce the amount of idle air.

If you don't see that, then either the stepper's gone, there's a wiring issue between there and the ECU, or the driver transistors in the ECU have failed. Likeliest of those three is the stepper. Subaru dealer will charge you silly money for one, Import Car Parts are likely to be cheaper. Other than that, try breaker/eBay etc. Any 99/00MY JDM/UK ISCV will fit yours.

scoobiewrx555

Grade A Subaru for a used replacement ISCV. They test everything before putting it on the shelf. Their service is excellent, prices are good, and they send normally by next day/1st class delivery.

cts5555

Thanks guys.

I think the piston may have actually snapped off, since you mention it is a stepper motor type not piston type, it freely moves forward and backward by hand, i can even fully remove the piston without force releasing the spring.

Either way, i believe this is the cause of the problem so will search for a replacment. Thanks for the quick and informative replies.

cts5555

SOLVED - Changed Idle Control Valve and now idles solid, wherever i set idle speed at with the PFC. Hunted for a few mins when first fitted, but now solid, i guess the stepper motor needs to 'zero' itself or something. Blip throttle and doesnt drop below set idle speed.

Thanks again guys.