Car not running properly

[bentara]

Hi,
I have a 2007 RS4 avant,blue 24k miles.
It has started not pulling/revving cleanly through the gears.
Driving normally its fine but when driven hard it starts hesitating/flat spotting from about 5000 rpm.
Its not misfiring or going off cylinders(i think)
I could have sworn it was a fuel filter but have put new one on,no different.
Has anyone came across this problem ?
I wonder if its fuel quality,never been able to find super unleaded to put in it but then i have done 5k miles since i got it on ordinary unleaded and it has been going fine.

[RS4KILLA]

airbox?

[neckarsulm]

wouldn't cause a misfire, tried 3 now with iffy flaps and all drive OK, owners knew no better.
Something makes me think intake manifold flap position sensors
Is StevieB still around as he told me his did this when he bought it and Audi replaced a sensor, could be intake manifold flap position sensor.
Needs a VAG COM scan for a start and then the hard bit starts!

[Terry1948]

It could be a vacuum issue so the power flap and the manifold flaps are opening and closing when vacuum builds and drops off.

[neckarsulm]

This is a corker of a thread, 2 cars, 2 new engines, both still hesitating! Fixed in the end...

http://www.rs246.com/index.php?name=PNp ... e&start=45

[approved]

i did the exhaust mod and mine did this...i put it back and it worked perfectly...

i obviously didnt do it right and caused some vacuum issue..

[neckarsulm]

i did the exhaust mod and mine did this...i put it back and it worked perfectly...

i obviously didnt do it right and caused some vacuum issue

indeed!
the vacuum that operates the exhaust flaps also operates the intake air changeover flap aka power flap and the intake manifold flaps.
If you disconnect the pipes from the exhaust valves but don't block them off then the vacuum pressure in the system bleeds out and is insufficient to operate the manifold flaps and the power flap.

[bentara]

Thanks for the replies there.
I thought a bit before buying this car with no warranty,hopefully im not in for expensive engine repair at 24k miles !
I tried it up the road again,goes flat at 5k revs and does not light up at 6k as it should do.
When i got back to house and had it idling when i stab the throttle quickly on and off it makes a suction sound,dont remember hearing that before.
Its the same sound that you get when you have the air filter off an engine,(in your youth)
Is there any point in taking this car to a dealer to be charged a lot of money and find nothing or go to a decent rolling road.

[neckarsulm]

Sounds like a vac leak.
Where are you based?

[bentara]

Im in N Ireland,have a dealer 4 miles away think they are £100 per hour or there abouts.

[neckarsulm]

Buy VAG COM sharpish then!

[scaghead]

Thanks for the replies there.
I thought a bit before buying this car with no warranty,hopefully im not in for expensive engine repair at 24k miles !
I tried it up the road again,goes flat at 5k revs and does not light up at 6k as it should do.
When i got back to house and had it idling when i stab the throttle quickly on and off it makes a suction sound,dont remember hearing that before.
Its the same sound that you get when you have the air filter off an engine,(in your youth)
Is there any point in taking this car to a dealer to be charged a lot of money and find nothing or go to a decent rolling road.

defo think it is something air/vacuum related .dont panic just yet like neckurslum said get it vag-commed..

[bentara]

Sorry,What is VAG COM ??

[Terry1948]

First check to see if your cars had the exhaust vac pipes disconnected if it has make sure they have been properley sealed. Vag com or VCDS as it is now called is software that allows you to interrogate the car and make changes to how it functions. It is a good investment even if you only use it to perform scans and change your headlamps to tourist mode.

[PetrolDave]

Sorry,What is VAG COM ??

Software for you PC and a lead to connect it to you car which lets you read and reset the fault codes on any VAG car. It can save you loads of money since you can diagnose many faults yourself without paying £100 an hour to a dealer.