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For the past week ive been going out to the rs6 every other day to find it dies as soon as i start it up when the revs drop back down. Its had 4 fuel trim faults and a random multiple misfire for a couple of weeks (no eml) but it does run rough when i start it from cold and hold revs on. As soon as its warm it runs sweet with no problems and ticks over lovely..

Any ideas?

I would be starting with sensors , first I'd be looking at the engine coolant temp sensor and checking it hadn't sh*t the bed .

Did you change the plugs and coil packs like you said you were going to?

Post up your fault codes.

The fault codes are as follows;

17538/P1130 - Fuel Trim; Bank 2 (Mult): System too Lean
17546/P1138 - Fuel Trim: Bank 2 (Add): System too Lean
17544/P1136/004406 - Fuel Trim: Bank 1 (Add): System too Lean
16814/P0430/001072 - Catalyst System; Bank 2: Efficiency Below Threshold
16684/P0300/000768 - Random/Multiple Cylinder Misfire Detected
16690/P0306/000774 - Cylinder 6 Misfire Detected
16691/P0307/000775 - Cylinder 7 Misfire Detected

Prior to getting these codes i also had the fuel trim bank 1 (mult) system too lean code and misfires on cylinders 4-8.
I cleared them and these come straight back up although i dont normally get the catalyst fault.

My original thought was maybe an air leak but as said once its been run for 10 minutes it ticks over lovely if it was an airleak wouldn't the constant rough idle stay there?

Definitely sound like an air leak. It's much worse at idle, but can smooth out when the engine is warmed up and needs less fuel - the trim can just about balance it out at warm idle.

Have a look in measuring block 32 and tell us what the 4 values are. Don't clear your codes before doing this.

Surely with a air leak the idle would stay high due to the extra unregulated air going in ? .

It doesn't. The engine reduces the fuel to keep the idle down.

Just come out and started the car up and its idling smooth. Seems to be a lot worse at really cold temps?

Yes, that's generally when idle problems are worse.

Shoppinit wrote:It doesn't. The engine reduces the fuel to keep the idle down.

So it uses fuel ratio to control idle speed rather than a traditional air bypass idle valve ?

The secondary air pump is also used for the first 10 minutes or so. Is that mapped out or removed? If not then I'd unplug it and see if it behaves differently.

Ajc wrote:

Shoppinit wrote:It doesn't. The engine reduces the fuel to keep the idle down.

So it uses fuel ratio to control idle speed rather than a traditional air bypass idle valve ?

Yes. No idle valve.

Just come out and started the car up and its idling smooth. Seems to be a lot worse at really cold temps?

Shoppinit wrote:

Ajc wrote:

Shoppinit wrote:It doesn't. The engine reduces the fuel to keep the idle down.

So it uses fuel ratio to control idle speed rather than a traditional air bypass idle valve ?

Yes. No idle valve.

I'm obviously more old school than even I thought .

crazymatty125 wrote:Just come out and started the car up and its idling smooth. Seems to be a lot worse at really cold temps?

have you checked the coolant temp sensor ? if its reading incorrectly then obviously fueling will be effected. Are the maf's seated correctly?