Strange issue with W211 E320 CDI

[w124coupe]

One for the technically savvy on here to ponder on and any ideas gratefully received.

A colleague has an 06 320CDI (V6) E-class which has a strange intermittent problem (verified by us as his passengers).

The car has good days when its smooth running and powerful, with clean gearchanges and good economy (41.x MPG on a run).

It then has moody days with jerky 1-2-3 (and 3-4 when pressing on) and 2-1 changes and 15+% worse economy on the same route (34.x MPG on the same run). Usually clears after a fuel stop or some other "engine off" stop.

Needless to say no stored codes and it has behaved when taken to dealer for him to "demonstrate the fault they can't reproduce".

Any ideas where to start looking for something that might cause this?

MAF has been swapped with another to no effect (on either car).

 

[BlackC55]

It may need a software update. I take it it is a 7 speed box.

 

[w124coupe]

Hi, yes its a mid 06 model with the 7g.

Up to date as of last service in April this year.

 

[davidjpowell]

My car has a jerky 2 -1. Only did a couple of times, but the dealer drained the oil which they said was burnt, MB replaced the gearbox. Hopefully your dealer checked the oil though.

David

 

[w124coupe]

Hi, not sure they did - I will ask him.

 

[Brian WH]

I had this problem with my E320CDI. The dealer finally had an updated software programme, which he then used and reset the ECU to read the gearbox changes better. They then took it for a run and let the gearbox/ECU adapt to the new settings. All Ok after that.