auto 220e revving/ jerking in drive at a stop

[liammoser99]

Hi, I have just come into possession of a 1993 Mercedes 220e automatic and have noticed that when in drive and I brake to a complete stop with the brake fully depressed the car is revving/jerking forward. My knowledge of cars is very limited and this is my first automatic car so not sure what the problem could be but am pretty sure it's not normal. I appologise if I have also put this in the wrong section.

Many thanks in advance, liam

 

[Doug1234]

Air leak on the induction side ,basically I would expect the engine is able to draw air from the servo and this causes engine revs to rise.

On a petrol engine you regulate airflow to control engine revs ,so somewhere along the line the engine is getting air from the servo when the brake pedal is pressed.

Someone else will be able to elaborate on it better than I can explain but putting gearbox in neutral and pressing the brake pedal with the engine ticking over should cause the revs to rise and fall.

 

[liammoser99]

Thanks for the reply. Will this cause any long term damage if not fixed and Is this an easily fixed problem/relitively cheap or are there different scenearios that can cause the air to leak?? I will be getting it looked at next week but I like to have a basic idea of what the problem could be before taking it to a mechanic and being taken advantage of due to my woeful knowledge of cars. Thanks

 

[television]

If the RPM at idle is too high then hard to hold the when stopped. on the inlet manifold you have the head lamp raising and lowering, and the gear box modulator connections, if the box pipes are off the gear changes will be very hard and idle high

 

[Peter C1974]

The throttle body may require cleaning.

One of my previous W124s, an automatic E200, would jerk forward just as I was about to come to a standstill - is this similar to what you are experiencing?

Remove the plastic pipe that extends over the top of the engine (from left to right), spray lots of carb cleaner into the throttle body, which is the silver object with a butterly valve to the right of the engine. If the valve is gummed up with black deposits the butterfly valve does not operate properly causing the symptoms I experienced. 10 minute job and a common fault affecting many W124s.