one thing i was thinking about. ive heard people say that they get idle problems after switching to different weight oils. like from a 10w 30 to a 20w 50...



so im thinking thats from different oil pressure. i dont know... but heres how i have my oil cooler i put it. but the thing is. i have it feeding the bottom and returning out the top. maybe this would cause added pressure along with running a 20w 50 oil??? this is kind of far fetched. but i pretty much tried everything... im open to ideas here...

 

and im just gonna throw in a few pics of the car cause im bored and i want to drive it... although it drives just fine and i cant find anything else wrong with it. i would rather not drive it with the bouncing idle.

 

Did you convert that to Right Hand Drive? (That is cool).



I'd suspect (I know you don't want to believe this)... You have a air leak somewhere. Assuming you have tested that BOV.



I had simular problems, When and bout a rubber quick pipe coupler at the local hardware store, and a 3" pipe cap and Air Compressor fitting.



Hook all that together to your INTAKE side of your turbo. Drop your Air Compressor regulator down to 5 PSI. You'll hear and feel all the leaks in your system. I have a broken throttle body gasket and loose clamps to my Intercooler, even though they seemed tight.



It was the best $10 I'd ever spent at the hardware store.



This isn't mine... but this is kinda what it looks like, Though I tapped my Air Compressor fitting on the end. I just drilled a hole and ran the threaded piece into the plastic.

 

well to better access the manifold and TB with the water hose. i removed the intercooler, BOV, and stok piping. and ran a different set of pipes coming out of the turbo to the TB. no openings, no BOV. then let the hose run water all over the motor. even tried spraying at the fuel rails to see if there were leaks there... nothing



but its worth a shot making a pressure tester. and if i put a gauge on there and let it sit. i could just see if the gauge goes down. that would let me know there was a leak if i couldnt find it on my own...





im down to thinking something electrical

 

and yes i converted it over...

 

did you check your cromets for air leak? i have also found the oil injectors causing a vacuum leak.

 

loosen the pivot arm on the secondarys on the throttle body and let the plates relax. sounds stupid but that fixed my idle surge.

 

i was going to say that... if the secondaries are opened, it will surge like that



another thing to think about, is that the S5 ecu is weird, it does unexpected things.



so the idle is supposed to be 750+/- 100rpm. the ecu has like a target BAC valve duty, that with the right idle setting will land the idle right at 750.



if it is within 100rpms or so the ecu can figure this out.



if its further off, then the ecu does strange things, like surging.



but id put a stock non tampered with TB in there, and see if that helps

 

i thought about swapping in an unported oe just to see. but i sold the extra one i had a day efore i got this car running...

 

thats the problem for sure then