Rapid idling on a R32

[Richo64]

I was wondering if anyone else has had this problem. I have a 2007 Mk5 R32. Lately, the idling revs for no reason jumps from the normal value of about 600 to about 1000. It's not related to the aircon, and when it occurs, I find the gear changes are altered in so far as I can't change from 5th to 6th until about 65km/hr (usually can change at a lower speed). I thought it may be related to the engine cooling fan, but it has now happened once soon after a cold start. I had it looked at with my last service with no fault found. I was hoping someone else could shed some light on this before I go back to the service dept.
Thanks.

[bazzle]

Can you do a VCDS (VagCom) interrogation on it?

Bazzle

[Richo64]

Was already done by the service dept. Found nothing.. said everything was ok.

[CatonaPC©]

I'll have a shot in the dark here. It's a faulty sender unit on the flap on the airbox intake unit. If that's jittery, it can tell the ECU the engine is still cold and rev the engine. That would explain also why your gearbox won't change up.

As I said, it's a long shot.

[POLARBEAR666]

Sounds like the R32 is having a heart attack due to being grossly obese compared to its mk5 siblings.

[Richo64]

Thanks Rick... interesting thought.
And yes POLARBEAR666, your disclaimer seems quite accurate.

The more ideas the better... hopefully this can give the guys at VW something to work with.

[Maverick]

Thanks Rick... interesting thought.
And yes POLARBEAR666, your disclaimer seems quite accurate.

Lower capacity all round with the 1.4's.

The more ideas the better... hopefully this can give the guys at VW something to work with.

How long does the problem occur for? Does it last until you turn the car off or does it only occur for a period of time (random or fixed)? Does switching the car off and on stop the problem?

[CatonaPC©]

If you ask me, I wouldn't mind having an obese R32!

[Richo64]

Seems to be random, usually after I've been driving for at least 25 min, I'm not sure if it stops after stopping the engine & restarting. It lasts about 1 min, then revs settle down to about 700, which is still a little higher than normal. I do a lot of motorway driving, but when stuck in the traffic in Sydney it's a real pain.

[POLARBEAR666]

Check the fuel filter.

If you have crap in the filter it can move around and sometimes clog it enough to cause a bit of idle issues.

Does it ever feel like it cuts out a little sometimes at higher revs?

[Richo64]

Thanks for the replies.
The fuel filter was changed at the last service... unfortunately didn't help. When it idles fast I have turned off the engine, then restated... seems to fix it for a while....

It may be a sensor as described by CatonaPC©.

[Richo64]

Just some follow up in case anyone else has this problem. It was the alternator... apparently was on the way out. Had a new one fitted & all is sweet.

[gregozedobe]

Thanks for letting us know what the problem was. I guess this is one of the "cons" of having smart cars - if there is a problem with the voltage supply (or earths) on any of the electronic brains then all sorts of weird stuff can happen.