Thread: Revving on Idle

Hi all,

Don't often comment on here but use this site a hell of a lot for help and ideas, but this time I really need your help. My Car 58 S3, as of last night decided to start revving whilst on idle, I found a clip on youtube which is doing exactly what mine is, can any one shed some light onto this? Had a service about two months ago, at 38K.

Erratic idle 8P Audi S3 + Fix - YouTube

Thanks you for any help, just want to see if it's something I can do or is it going to be a trip to audi for them to pull my pants down! BTW I know how to drive a car I have no idea of fixing one so please go gentle!

Cheers

Lucas

Probably not what you want to hear but first step is always VCDS to check for faults logged before you then look for an air leak somewhere on the induction side.?

Has to go to Audi then for that?

Hi Lucas, it doesn't have to go to Audi for a diagnostics check. Lots of members all over the UK have VCDS, have a look at the VCDS Users Map and see if there is anyone local to you who can plug your car in to see what's wrong, for the cost of a few tins. Depending on what's up - as Paddy says, it could just be a split vacuum hose - you may not even have to resort to taking it to Audi at all. xx

***VCDS Users Map***

bet i know what this is! had this on one at work.
under the airbox engine cover. bolted to the front of the rocker cover with 4x 20 torx is an engine breather valve. there is two pipes clipped on to it. one from the engine breather under the inlet manifold. and one directly from the inlet manifold.
the one i looked at last week.... the valve had gone faulty allowing the crankcase to be subjected to the full vacuum in the inlet manifold.

it had fault codes; misfire detected on all 4 cylinders, mixture too lean and induction system air leak.

i replaced the valve unit (£29 from tps) took 10 mins. cleared codes. idled perfect again.

if its idle hunting its more than likely the air flow meter but it looks from the vid its trying to stabilise so maybe a vacume issue

simple test.... without having to strip anything, with it idling can you remove the oil cap? normally you can quite easily.
but..... i suspect in your case... you can twist it to undo it but at that point does it feel held down by vacuum?

Thanks all I will try your tip Murran, it is strange as its only happening one in three journeys, on the way to work this morning it was fine yet last night coming home from the gym it was revving, which is horrible when you drop to second to slow down and because the revs are holding it at 2000rpm its driving like an automatic!!
My friend works at Seat so I took it to him last night to plug it in and he said no errors, but typical it wasn't revving to show him.

Just heard back from my mate at Seat and he said that their was an error code and it said it was the Throttle Body, I really know nothing about cars, what is it and how much! lol

What about the throttle body???.

If it needs realignment you can do this on VCDS. I drive through Swindon once a week on my way to Cheltenham but not due to go again till end of next week.

Can he tell you what error code?

Where abouts you from then Warren, do you have VCDS?

Originally Posted by LucasS3

Where abouts you from then Warren, do you have VCDS?

You have PM

Cheers Warren. Will keep you all updated on what it is and what is done to fix the problem.

Murran you were absolutly right, tried to pull the Oil cap off could hardly move it then a big intake of air as I freed it. Right so is this something I can do easily enough what you explained? And where would I get the part from?

you can get the part from the dealer. or tps directly. Trade Parts Specialists. i dont know the part number of the bit you need tho. youd have to explain what it is and where it fits. im sure theyd know from a brief description......
reguarding doing the job. the only difficult bit is pulling the top engine cover off. theres an intake pipe on the top left (theres two spring clips holding it on) and you'll need to unplug the airmass sensor (the plug near the pipe youve unclipped)
the engine cover is mounted on rubbers doofers that pull off/push on. get hold of the cover at one corner and pull it up, then do the other corner. the rubbers can get a good grip tho. so dont be scared of giving it a good yank! (a tiny smear of oil in the doofers when you put it back on, likewise the seal on the inlet pipe.)
you can now see what your changing. the valve unit. its black plastic with a round disc/valve with two pipes clipped to the unit its on the side of the rocker cover facing you almost on top of the inlet manifold.
to unclip the pipes you pinch the clippy bit at each side to release the pipes. and like i said theres 4x t20 torx screws holding it to the rocker cover.
fit the new one, make sure the rubber gasket to the rocker cover is still inplace and try not to drop the screws! the one on the right is slightly hidden/awquard.

Can the PCV cause vacuum issues?

the pcv valve is the valve the unit.

You are all being a great help I will give this ago, Warren hold off for now I will see if this works what Murran is describing, for the sake of £50 its worth ago.

Great to see the guys all helping each other out as usual. This site is full of love!! xx

Update, Murran, you were right I got the Valve & Gasket from Audi then took it to a friend who fitted the part in 10 mins like you said, the hardest thing was getting the bloody engine cover off, nightmare, be easier next time as greased up now!! But fixed the problem right away, no more revving on idle, case closed.... A big thanks

thats brilliant! did you delete the fault codes after?
can you now remove the oil cap easily with it ticking over? does it upset the idle when you remove it?

No fault codes funnily enough! The funny thing is it really is a 10 min job, but my god how hard is it to get the engine cover off!!! Drove it round the block after he fitted the new valve and was great, checked the oil cap after there was a little suction but the mechanic said that was normal, but it was 100% easier to undo than before the new valve. I certainly owe you a beer, you saved me a lot of money.

Spot on mate, glad its been resolved. Good skills Murran!

strange that it had no codes.
the one i did at work had misfire detected cyl 1,2,3+4. a weak misture code and a unmetered/air leak code.

wierd!

Originally Posted by murran

bet i know what this is! had this on one at work.
under the airbox engine cover. bolted to the front of the rocker cover with 4x 20 torx is an engine breather valve. there is two pipes clipped on to it. one from the engine breather under the inlet manifold. and one directly from the inlet manifold.
the one i looked at last week.... the valve had gone faulty allowing the crankcase to be subjected to the full vacuum in the inlet manifold.

it had fault codes; misfire detected on all 4 cylinders, mixture too lean and induction system air leak.

i replaced the valve unit (£29 from tps) took 10 mins. cleared codes. idled perfect again.

Hi Murran, Suffering the same issue with mine! can i do this oil cap check with the engine cold??

thanks in advance!!

right just been out to try it cause im impatient and you are spot on! was a suction going on then as i pulled it out it let out a burst of air!! the idle was affected by this too. Going to call TPS now. Anyone got a part number for this valve!? i also need a new cam follower so can kill two birds with one stone!!