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Matt
Matt, Mechanical Engineer
Category: Mercedes
Satisfied Customers: 22160
Experience:  BEng hons Mech engineering, in auto industry 22 years
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I have a mercedes 280 e class and I have a problem. If at night

Customer Question

I have a mercedes 280 e class and I have a problem. If at night I drive about 45 miles at speeds of up to 80 miles/hour mostly on motorway and dual carriageway and I then come to a roundabout where I stop. When I try to pull away I appear to have no power. If I switch off the engine and restart it the car returns to normal. What is the problem and should it be dealt with immediately and the approximately cost.
Submitted: 3 years ago.
Category: Mercedes
Expert:  Matt replied 3 years ago.
Hello

This sounds like an electrical actuator or sensor at fault .Usually when you can cycle the ignition key on / off and then restart the engine and the fault is gone temporarily this indicates that this is an electrical component causing this issue.

This could be a wiring issue as things tend to expand when hot and its possible a poor or partial electrical connection is being pushed apart on one of the major sensors so check the connection plug and wiring to the following;
Airflow meter
Crank position sensor
Cam position sensor
O2 sensor
Throttle position sensor


Also worth checking the connections to the fuel pump for the same reason - unplug each in turn and give them a good squirt of switch / contact cleaner - Not WD40

and also unplug and inspect the main power relays and fuses for signs of overheating or corroded terminals - so the ones for the ECU and the fuel pump

And also unplug the wiring loom connections in the engine bay one at time and inspect for corroded or recessed pins.
Also replace the spark plugs if any of them fail this checklist:

http://www.ngksparkplugs.com/tech_support/spark_plugs/faqs/faqread.asp


Also its worth checking that the electric pump that feeds the injectors is working correctly, it should run for a few seconds then switch off when you first turn the ignition on. If the connections to this are corroded or damaged then the pump could stop at any time. 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 voltage at the pump and check its getting 12V