Audi A4 B7 2.0 tfsi Quattro - Engine revving up and down when idling. Help please.....

[Doddawidd]

Hi all, been on this forum a few times looking and finally joined up.

i have a A4 2.0 tfsi Quattro avant, s-line special edition, 2006. Having some problems and don't have an Audi dealer near me, so any help appreciated.

Driving home from a short break a few weeks ago, the engine management light came on. At the same time, I also noticed that when stopped at a junction, or roundabout, the car idling engine speed would change from the usual 800rpm to around 14-1500, for a few seconds, then come back down again, sometimes to 1000, sometimes to 800, completely random. Also, when I take my foot off the accelerator to change gear, it takes maybe 3-4 seconds for the engine speed to decrease back to normal, so it sounds like I'm slipping the clutch all the time.

When I got home, I took it to the local garage who put it on the computer. He said there were a load of alarms in, but couldn't decipher what had exactly had caused it, so reset the fault codes to see if it would come back in again.

Ran it again and after a few days, the engine management light came on again, so I immediately dropped off at the garage. There were two fault codes standing;

Idle control system: engine revs higher than expected (didn't catch the fault number)
also, an alarm regarding a clutch switch fault.

The garage has ordered a new clutch switch, 19 quid, and should be here In a couple of days, so I'm running the car again. They reset the engine management light and hasn't come back in for a week now.

The engine revving itself up and down and the failure for engine speed to come back to normal is really annoying.

I also noticed today, a kind of flapping noise coming from somewhere when up above 60mph? It seemed to be coming from below the car?

On reading through this forum, I've kind of leaned towards a diverter valve issue? Sorry but I'm a spark to trade so not 100% familiar with engines.

appreciate any pointers that anyone can give me on this one.

Thanks all, much appreciated

[the newb]

Mine was doing a similar thing with the fluctuating idle, my problem was the pcv valve. An easy way to test was with the engine running to loosen the oil filler cap and if quite a bit of suction then it's the pcv valve that needs replacing.... Another thing that affected my idle was the exhaust sleeve was corroded and leaking air, didn't sound like it was blown but must of been bad enough for it to affect oxygen sensors (exhaust sleeve near the front) that's about as much as I know mate hopefully something simple like that

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[the newb]

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[Doddawidd]

Cheers mate. Will pass the info on to the local mechanic. Will hopefully point him in the right direction

cheers again

[the newb]

Any joy finding what the problem is/was?

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[Doddawidd]

Hello again mate. The mechanic replaced the clutch switch yesterday and reset the engine management light. The old switch had failed, as had thought.

ive been running it for around 60 miles today and the engine management light hasn't come back on. However, the idling issue is still there. When the engine is cold, then it's fine, it's only after you've run the car for 10-20 minutes that the fluctuations start. Really annoying.

once I get home on Friday, then I'll pass on the info you've given me and see what we can look at next. Will keep you posted.


cheers

[Doddawidd]

Guys, just to let you know....

Got a fix for this problem and it was indeed the PCV valve. The part itself was around 40quid plus the mechanics' time tifit. Car is running smooth again, no engine warning lights, no engine revving up and down. Brilliant.

Thanks for your help guys

Cheers