Thread: GTI-R idle surge issue

Hey guys,

I'm helping a friend who got a GTI-R and he's having issues with idle and engine is running rough in general. Idle keeps bouncing between 1000-2000rpm, it runs rough and if you accelerate up to some level the rpms get stuck at really high rpms (as shown in the video bellow).

I've uploaded a video to show the issue.



What we have tried so far:

- cleaned MAF sensor
- checked vacuum lines (still not 100% sure its good)

Appreciate any input!

Checked TPS today which seems fine, 0.45v without throttle and over 4v with gas pedal floored.

It seems that there are several vacuum lines behind the intake plenum which need to be checked

Also, a RHD to LHD conversion was done it seems that they messed up with most vacuum lines so I was wondering, Is there some kind of map o guide to all the stock lines so we can check everything??

OK, found the vacuum routing map.



I'll be re-testing the vacuum piping.

Take of the throttle bodies and shine alight from the back side and look for a halo if you got halo's of light coming through that a problem that needs to be addressed, throttle blades should be 100% sealed the IACV is the sole supply of air when throttle is closed contrary to popular belief that there should be a small gap is wrong EFI engines, there is a dry sealant/lubricant for this actually, most people have a gap and have compensated for hi idle via the idle adjustment screw to compensate for this gap that grows as wear incurs until it because to much of an air leak that even closing the idle adjustment screws does not bring the idle down anymore. Its called Molykote D-321R but its expensive.

the issue has been resolved, it was a huge vacuum leak. But nonetheless it's a great idea to shine light to look for vacuum leaks.

Thanks for the reply

Mind telling where was the vac leak specifically

I don't really know because we disassembled everything from the intake manifold to the air filter, but there were some cracked vacuum hoses behind the intake plenum, specifically the ones that come out of the vacuum concentrator (you can see it in the picture in my post above, behind the plenum, the one that is closer to the oil pump, it has a pink hose going to it).