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Hi guys,


As part of the general work on my project GC8 (thread below) - I'm trying to resolve an issue the car seems to have at idle.

Essentially, it runs beautifully from cold, and when driven (any throttle application improves the situation). However when warmed up, the idle will drop to the point when it's struggling to run.

This can manifest as the car stalling when the clutch is depressed during driving.

As a test I've tried unplugging the MAF, this makes things worse. No check engine light is shown.


To complicate matters as you might see from the build thread, the chassis is a phase 1, the engine/harness/dash/etc is later model (V6) STI.

To me it seems like a sensor issue of some sort, possible air temp? I'm still trying to work my way around EJ20s.


Any help gratefully received!


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Does it still run when unplugging the maf? Not very scientific but if it stalls it's good,

Proper way is to test it with a multi meter,

Could be one of many things, iacv maf throttle sensor, map sensor split hose etc, I'd start with the cheap options checking for leaks then move onto looking at the rest of it,

Is the fueling correct ? From cold they have an auto choke, maybe when warm it's not getting the right mix ?

Sent from my SM-G930F using Tapatalk

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It still runs with the MAF unplugged - but (even) more lumpy.


I'll try cleaning the IACV, this looks like a simple first job. 

To answer your other question, idle is high and the exhaust smells super-rich from cold.



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Standard on the cold idle & richness once warm should drop to about 750-800rpm

What colour label have you on the maf ?

May be worth seeing if you can borrow one of the same type to test, I'd hedge a bet it's that on its way out,

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Would appear to be label-less! :-


The car did have a new (second hand however) MAF fitted before it came off the road, but this was 3 years ago - and I don't know the provenance of the one fitted.



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