At WOT in 3rd/4th/5th the car has started accelerating in a very strange way. Up to 3.5Kish it pulls fine but then the engine starts to accelerate very quickly, up to around 5K, then falls back down a few hundred revs, then climbs steadily again - VERY weird watching the rev counter go down yet still accelerating.

It's not just the dash as the engine is making acceleration like noises. Has anyone any ideas? It only seems to do it on full boost, but I've cleaned the controller, reset ECU etc. and still the same problem.

Help!

 

Hi KRM
The way you have written it, sound like clutch slip.
The engine pulls/revs up quick from 3500 then as the speed of the car/transmission catches up the revs, they seem to drop but still you are accelerating.... This is just the pressure plate over coming the slip... sounds like new clutch time.

Len
S4You.co.uk

 

Hmmm, never thought of that, makes sense though. Would it also happen if I held the revs at say 4K then booted it? Any other way of testing without taking the clutch out?

 

Maximum torque is around the revs you've indicated, add to that some load from a higher gear and you have the perfect ingredients for clutch slip. To check for sure, you should find it worse in 5th, and also if you're driving up a hill...