Mercedes Repair Questions? Ask a Mechanic for Answers ASAP
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1st simple thing to try is cleaning out the throttle body as they can stick if clogged up with carbon and fuel deposits
if thats OK then check over the throttle wiring for any damage and corroded connections
you can also do a check by removing the inlet pipe so you can see the throttle and then switch on the ignition and have your assistant slowly push down on the throttle
the throttle blade should move smoothly with no jerking or sudden movement
if there is any of the above then replace the throttle
and if thats OK then it could be a lack of fuel pressure from the electrical pump at the tank.
If the connections to the pump are corroded or damaged then the pump could stop at any time or could not be running at full speed. Check that its relay switches in and out and the relay contacts are clean and bright – replace the relay if in any doubt and do the same for the fuse,
Ideally measure the pressure at the injectors and if this is low check the pump as described and also consider changing the fuel filter as if this partially blocked this too will reduce pressure.