H. I bought a gc8 2000 GT with 200400km 2 weeks ago.
The car idle rough and the car shakes, but only when the engine is warm.
Previous owner said it began after he had a engine wash? Idling speed is fine for a while, then it settles down 550 to 400rpm and stays there, sometimes it dies out.

I try to clean maf and icv, but didnt improve.
So I bought a new icv from ebay but didnt improve either.
Cant find any vacuum leaks.
Disconnected battery for 20min to restart ecu.
There are no fault code.

Car spec. Sti panel filter, 3 inch exhaust, decat. Car pulls good, no other problems than the idle.
I have a ecuExplorer log when it idle.

I have never worked on a subaru.

 

I would buy a new maf first and foremost. A failed maf will throw a fault code but a failing one will not and a failing one still has the potential to "end" your engine!

 

as above i had a skyline that done this and it was the maf sensor

 

Okey, so I'm thinking about to buy maf and ecu coolant temperature switch from ebay.
I have heard much bad things about ebay parts. But its 12mnth warranty, so it must be good. The ecu temp sensor supposed to have something with idle too.
I noticed the radiator fan does not run when standstill, even in working temperature. Normal?

 

could be engine temp sensor if you definetly know the fans are ok.