Air leak-Vacuum issue PCV-Mystery part?

Calin Lapugean

Registered User
Feb 17, 2018
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Hi all

New to the forum so please be gentle :thumbs up:

I'll try do describe the issue the best I can.

The car is a A4 2.0T 58 plate with 110k on (had it since 55k and sweet as a nut until now)

The issue started with one day the Engine Management light coming on. The engine felt absolutely fine at the beginning. Idle OK, no oil consumption (other than than the normal ) Pull ok, no funny noises from the engine bay. As I am using the car for work and couldn't go in to have it properly checked for few weeks I ask for advise (local garage over phone) and was advises that if the EML is no flashing and if the car feels fine it probably is just a sensor (O2 etc..) and should be fine driving it.

About 1 week later I noticed a whistle / air leak noise but only when outside of the car. Tried to figure out where from but couldn't place it. As I was away with work planned taking it to my garage in 2 days when back. Engine still felt OK when driving but started running a bit rough on idle (the RPM needle was still sitting solid at 1 line below 1k but every 1-2 seconds felt like a misfire). However it wasn't doing it all the time. Pulling up at the traffic light was noticing it 1-2 out of 5 times. The air leak noise was also intermittent with the engine running sweet when no noise.

2 Days later the engine started running a lot worst on idle with big(ish) shakes more or less all the time and whistle all the time and the engine started revving itself on idle (up to sometimes 1800 revs and then dropped down sitting slightly under the normal). Looked into it and found out about the faulty PCV issue. Checked and the engine was running under vacuum (was not able to remove the oil cap on idle) and after taking the engine cover off I checked and the whistle was coming from the small tube at the top of the PCV.

IMG 0655 copy

So went ahead and got the PCV replaced (above is the new one) and the whistle straight away stopped, had the codes cleared and the engine stopped revving itself. So though problem solved. Also only after the fix I realised the pickup at low revs was also affected during the fault as the car was seemingly faster after.

About 4 days later the EML came back on again. I could again hear a whistle when outside of the car so straight away went to check the PCV suspecting faulty OOTB part but the whistle was not coming from there any more but for the life of me I could not place it. Had a look at all hoses but no joy. Checked for vacuum and there didn't seem to be any as I was able to undo the oil cap. After few days though it started shaking on idle again and there was vacuum again. Had the error codes checked again and same. Air/Fuel imbalance. Engine pick up at low revs has suffered again

After a very long inspection I found where the whistle was coming from this time around.

IMG 4957 IMG 0655

After checking it out I figured I could easily press it in and would just pop back in place.

Feb 17 2018 12 54 43

Instantly the whistle disappeared, engine was no shaking any more and the power at low revs came back to normal. Cleared the codes and was all good for all 50miles then EML came back on, whistle was back with the engine lacking in power at low revs again. Checked and it was in the same popped out position.

I tried looking into what that exactly is and couldn't find a straight answer so was hoping one of you could help. :bye: Looking for something that you haven't got an exact name for is rather tricky..... From what I gathered it's to do with the intake manifold swirl flaps but can't figure out what's the normal operation (is it meant to open to release pressure at some point but then close back and that's what faulty, or is it never meant to open and whatever was supposed to keep it in place has failed?)

Any thoughts on this would be great as it's driving me crazy and can't imagine it's doing the engine any good.

Sorry about the long post but wanted to be giving you all the facts :respekt:

Thank you

After some more research. it seems it's part of the linkage for the Intake Manifold Runner Flaps where the wear and tear on the plastic part is causing to pop out from the pressure. Supposedly they do not sell the part separate so a new manifold would be required. Feels rather silly of them not to when the repair would have been significantly cheaper.

A Runner Flap Delete kit might be a 2nd option as you can pick one up for £50.00 and it's meant to give some 5-10BHP and the kit would solve the issue as the part gets replaced by a plug. Have heard mixed reviews though with some complaining about increased oil consumption and cold start issues without a remap.

Anyone experienced with one? worth it or shall I fork the cost of a new manifold?

More on the "popping" issues in the below vid (around 3 mins into). Thought it could help someone.

Thank you


As I have not got that engine, I might just be talking through a hole in my head, but is there not an aftermarket supplier for a repair kit?