Mercedes E320CDi help required

[Bigdw]

Hi Everybody
Can anybody help, my E320cdi W210 has developed a problem, when driving at 60 MPH or higher if i take my foot off the accelerator pedal to let the car slow down, the rev counter jumps up a couple of hundred revs just for Half a second, which makes the car jump, the revs then drop back to normal, it does this nearly every time i take my foot off the gas at high speed, the engine does not sound lumpy at any revs and it accelerates smoothly with no loss of power and is not smokey, the only other thing i have noticed is that from a standing start when putting my foot on the accelerator the take up on the gear box/diff goes with a light thud as if theres a flat spot when just above idle speed, though the revs at idle and thoughout the accelerator range seem even. there is no surging anywhere in the rev range, just the blip when taking my foot off the gas at high speed.
Any help much appreciated

 

[BlackC55]

This does sound like a gearbox problem.

Needs to be plugged in firstly.

 

[Bigdw]

Hi BlackC55 I assume you mean its dropping a gear when the fault occurs, because it changes gear very smoothly and doesent feel like its doing that, more like a flick on the accelerator pedal

 

[Mercgaz]

Same with me 03 plate e270, seems hap po en around 20mph mark, rev counter hunts slightly on occasion.

 

[Bigdw]

Hi Mergaz
going to get the fault codes read on mine this week, im starting to think throttle Position sensor, I assume it works on a potentiometer principle, we use pots for speed control where i work and they occasionally become worn and the drive speed jumps at low frequency