[Mk2] [Turbo] Advice/Experience wanted - Rev 2--> 3 Swap won't idle / poor idle

[Danbob]

My engine is all back together and has done 500 miles of running in, but still won't idle right. Would like to hear other peoples experiences especially where a solution has been found.

Background
ST205 head
Rev 3 Turbo harness
ST205 ECU
HKS 264 cams
CT27 turbo

Running sweetly through rev range, only has a problem at idle.

will idle at 1000k no problem using throttle, but will not control idle by itself.
needs a dab of throttle to start up, happier idling cold than warm


Will hunt between 400rpm and 900rpm continuously, stalls if you come to a stop when engine warm and when clutch or brake pressed, anything that upsets the delicate idle.


Have checked and confirmed that TPS is set correctly.
Confirmed throttle plate set screw is set correctly
Checked for major vac leaks (of course could be some hiding)

Would make sense to remove IAC and clean/test that, but I'm suspicious that it's more likely to be something electrical

Anybody else had this with a gen 2 --> 3 swap?
Anybody experienced similar symptoms and found a fix?


Cheers
Dan

[pbmr2]

hunting is a classic air leak. had this myself, turned out to be a leak on the idle control valve where it had cracked.

seen it a number of times and it's alway a combo of idle valve any/or intake side air leak.

Not had it on a swap as not done that swap, but have seen it on ren 1, 3 and 3.
pocket money on an air leak. if that leak is caused by the idle valve or the valve being gummed up plus trying to compensate for an air leak, not sure.

[Danbob]

Yeah that does make sense, I hate searching for vac leaks, guess I'm my head I've been trying to put it off.

Will break out the boost leak tester and rule that out first!

Cheers

[killerferret666]

Got exactly this after a swap, so at least I know what to look for now.

DanBob did you find the problem?