190D Slightly surging

[kamil]

My 1985 190D 5 Speed (160K) seems to be slightly surging from the sound that comes from the engine. The RPM needle does not move at all but if you listen carefully you can make out the noise. I made sure all the accessories in the car were turned off so that is definitely not a culprit.

Anybody have any idea as to what it might be ? The car does run fine and starts perfectly.

Thank You

[Gilly]

My idea is that some models, on the injection pump have whats called a rack dampener, kind of smooths out the rack which controls the pistons in the pump. If it has it, I bet it's your problem.
Easy to adust.
Gilly

[sailor15015]

My 85 300D has the same surging problems occasionally while idling. The tach doesn't move but the oil pressure needle will move up and down slightly in time with the noise. Will adjusting the rack dampener fix this? If I raise the idle with the pedal ever so slightly it clears it up and the wobbling that comes with it.

[t walgamuth]

i dont know about the other thing mentioned above but my first thought was an air leak into the fuel lines.

[kamil]

I don't have air in the filter though so an air leak is probably not possible... but you never know