My W140 has had this problem for a while now...it's not bad but gets worse as the weather gets warm. I'd like to get it taken care of. Also a friend with a twin 300SD says he has the same problem.

The engine will pulsate or rock at idle ever so slightly, just enough to make the car rock just a tad bit. It almost seems like it's matched to the pulsation of the lift pump. The condition seemed to be reduced (maybe) when I replaced the pump valve o-rings and seal washers but it's still there a little bit.

In the summer it's worse when the AC is on and engine heat is higher IIRC.

Off-idle there's no problem of the sort but I'd like to get it sorted out.

Any suggestions as to what the cause is? I searched through the forum but found nothing similar that I could draw from.

Forgot to mention the lift pump has been overhauled and IP has good pressure.

Thanks
Steve A

__________________
Steve A
92 W140 OM603
97 VW Jetta TDI
90 Passat variant TDI 6 speed MT
94 Chevy K1500 6.5TD
05 E320 CDI
+ others