It's the usual chestnut - poor idling - Hunting, idle speed drops to low, engine stalls etc. It tends to do it when the engine is hot. I think this problem is also giving me the violent hiccuping as I let the clutch up, unless I keep the revs high by slipping the clutch.

The car has a new O2 sensor, MAF and plugs
I've thoroughly cleaned the ISCV with brake cleaner
If I unplug the MAF, the engine doesn't stall, although it runs much rougher
I can't find any inlet pipe air leaks or pipe damage
The HT leads look to be in good order.

Don't know what else to do....There are no error codes.

I have a Blitz dump valve. I've seen comments they can give problems. Should I change it? Perhaps I should buy a new ISCV? Bet they aren't cheap though and they might not fix the problem. Perhaps I should ditch the Pipercross induction kit and install the standard airbox (better for the MAF?).

Getting fed up with these cars. Not enjoying ownership at present.

Oh yeah, it's an STi 4 Type R.

Anyone any advice or words of encouragement?

David

 

If the Dump Valve is a single piston one it can give very bad idle i suggest try changing that to a standard one or one that is definatly twin-piston or that you know works fine on a Impreza.

If thats not the problem try removing the induction kit and fitting a standard air box, if this caused the MAF to break then it could have done it instantly to the new maf.

 

How do I know if the dump valve is a single piston?

Thanks

David

 

I have a blitz dump valve fitted to my m/y94 wrx. They are single piston and mine also has idleing issues. The fault is cured when the original recuiculating dump valve is fitted.