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Can anyone hazard a guess as to what might be causing a problem that has just returned to my RS2.

To cut a long story short the car cuts out when decelerating for a junction/roundabout etc. I had this problem about 10k miles agao and we tried a few things, new alternator, new battery and cleared out the throttle body. The throttle body clean seemed to do the trick and I haven't had a problem since.

Having just driven 1,000 miles to France and back with no problems I drove the car last night to find that this problem had returned.

Any ideas????

does it start straight away whilst still slowing down? does it cut out when the revs are high using the engine to slow you down or when its at idle with the clutch in, say changing down?

It tends to cut out when the car's speed is <15 mph, never when the car's revs are high

The problem seems to occur at low revs, i.e. when changing down at low speed or when the clutch has been dipped prior to stopping at light/roundabout junction etc

The battery light then flashes and the power steering is lost

have you checked for boost leaks ?

Ignition switch possibly Tom ? http://www.s2forum.com/forum/showthread.php?t=53999

I had a similar problem, it was worse while the car was warming up too. It was as if the engine tried to catch idle as the revs dropped but didn't quite make it. I got rather used to blipping the throttle every time I stopped for lights, or bumping it in 2nd as i coasted up to them

I'm honestly not sure what cured it as I had a full engine rebuild and it's no longer an issue. I did spend some time cleaning the throttle body, which was rather gunked up, and ISV as well; I also found some minor air leaks around the injectors and breather system when it all went back together that were giving me a rough idle (not enough to stall it but it often felt like it would) and once solved the idle became solid again.

I did drive the Audi briefly a couple of nights back and did notice fluctuating revs on idle...I'm sure it did the same the last time I had the problem and when the the throttle body was cleaned out all was fine again but that can't have been more than 5-7k miles ago.

If it is the same problem and this is the root cause then how can I stop the throttle body clogging up with such regularity? Surely the problem must be one stage back...i.e. what is being fed into the throttle body? Can someone help?

Clean out the ISV. If problem still persists them perhaps a new ISV?
Crap fuel will cause this as deposits are left in the ISV.

Idle Stabilisation Valve...that's a new one on me, I'll look into that, thanks

Could possibly also be related to the fuel level running low due to incorrect message from my fuel gauge/on borad computer....picking up crap from the tank maybe? As we all know the RS2 is a thirsty girl and it doesn't take long to empty!!

Did a bit of surfing and found this thread....

http://20v.org/engprob.htm

I'll let you know if this tackled the problem as soon as I fiond the time to check this out.

Tom