Cold Starting

[gripper]

My V6 has recently developed a fault when starting from overnight or a period of approx 4 hours parked up ! Any ideas
Doesn't quite sound right on initial start up but always starts yet a minute or 100 yrds down the road she wants to stall revs drop with power but doesn't cut out.
A blip of the the throttle or a few seconds later and all is right as rain
No other running probs apart from this. No codes showing ! I figure its something to do with the cold start system but struggle to understand what is involved !

[UrS4boy]

Have to suspect a failing fuel pump, starting with its internal check valve allowing fuel to drain back into the fuel tank over night and then not being able to provide enough fuel while running. Suggest replacing it. I presume your V6 is an AAH or ABC in a CQ. If so, the OE fuel pump PN is 8A0906091G (same as the C4 UrS4/S6).

Here is some Fuel Pump info including how to test it, relay it (to increase the volts it receives) and replace it (C4 UrS example but B4 will be similar). (watch for the hyperlinks in the post to lead you to more info)

http://forums.quattroworld.com/s4s6/msgs/22623.phtml

[mcandmar]

That sounds a bit like a vacume leak. I've had it on S2's where there is a vacume leak and the ECU has a hard time working out how to regulate the idle valve. Usually what happens is you start the car from cold, drive down the road, then as soon as you clutch in to let it idle the revs drop below 800rpms and it stumbles before the ECU opens the idle valve to recover. Add in load from the power steering pump and it can sometimes stall. Does that sound like what your describing? Or does it do it when on steady throttle driving?

[gripper]

Have to suspect a failing fuel pump

I think you may be right
Spoke to someone today about the problem and he said fuel starvation !
Would the pump be in more or less in the same location as a S2 ?
I thought I read it somewhere that it was inside the tank accessible from an inspection hole under the carpet in the boot ?

[gripper]

Right got it ! Thanks for the info

Not cheap are they

[Rusty]

I've got a spare S2 pump you can try and see if it solves the issue. Not sure if it fits though...

[mcandmar]

V6 coupe uses the same pump alright, i ran my S2 on one for a while when the original died.

[gripper]

I've got a spare S2 pump you can try and see if it solves the issue. Not sure if it fits though...

Thanks Andy your a star
I will pm you my mob number over the next few days and we can arrange a meet.
I'll bring that door pull over as well although I still have not found the other side !

Thanks for everyone's help, love this forum,its better than having a Haynes manual