Replaced Water Pump,
Join Date: Aug 2009
Location: New Zealand
My 156 2.0 TS used to do this too. But hasn't since I cleaned very connector on every sensor I could find, and the connectors on the intake and variator actuators leads, as well as the 2 x multi-pin conectors to the throttle body. No more jerking or snatching... I used a special electrical/electronic contact cleaner recommended by one of our electronics engineers at work. He said solvents like WD-40, RP7, etc, were to agressive and left an oily reside.
As the sensors generally signal by way of minute changes in resistance, light corrosion and dirt at the connector can upset the values recieved by the ECU.
Another thing which worked on my 190E 2.3-16 was using Valvoline fuel injector in the gas tank great for unclogging the injectors. The Merc (which was a Bosch CIS-E so was mechanically metered continuous injection) would be rough and jerky just above idle on small throttle opening. If the spray pattern is not properly atomised due to fuel reside deposit build up (usually caused by fuel on the tip of the injector evaporating off a hot shut off engine), this will be most noticeable at low rpm/light throttle. The injector cleaner will do no harm, but use it sparingly. I usually put a bottle in the tank once a year.
Darryl in New Zealand
Last edited by KiwiAlfa156; 04-10-09 at 09:22.