1996 C4 2.6 .. Wierd electrical & engine behaviour??

[Yerfdog101]

Hi,

I hope you can help me, my A6 has started exhibiting some unusual traits. On a cold morning I will start the car & the engine will shoot up to 3000rpm , then as soon as the revs drop to 1600 it boost back up again to say 2k. The engine continues in this way until it is switched off.... which gives for a bumpy ride!!. Then when you fire it back up on a warm engine... it is fine.

Also on the odd occasion when starting the car the electric sunroof has decided to slide fully back without any provocation. I have then needed to wind it back manually by overriding the motor to get it to reset!....

I am wondering is maybe some damp is getting into the ECU electrics or could a dodgy battery cause these issues???