Engine hunting at a steady 30mph

[Bingy]

My W203 facelift c220 cdi

when driving along at a steady 30mph the engine hunts and the revs go up and down slightly.
Tickover is fine , Acceleration is fine as well as kickdown, it is just at a steady 30 or 40 mph the revs go up and down and you can feel the car in sequence with it.

 

[Bingy]

Does anyone have any info that might help?

Also meant to say it is a 2004 (54) plate

 

[Bingy]

Has nobody any idea of what this might be?

 

[paul73mt]

I have this I think, some have said the valve body in the gearbox could be faulty but an Indy has said to be its the actuator / Variable veins on the turbo sticking. Mine seems to do it when you gently push the go pedal when your going up an incline. Been in to Mercedes twice now and still say nothing wrong, once under warranty and again with my extended warranty.

 

[paul73mt]

Well just an update had a MB tech come out with me and 'felt' the problem waiting to have no4 injector changed so hopefully that was the problem

 

[whitenemesis]

Did he use STAR and read the codes?

 

[paul73mt]

Did he use STAR and read the codes?

no codes and the other 3 times it had gone in there were no codes so they didn't do nothing else. This time as the tech felt the problem expected an injector and side that there are 3 engine running tests within star