My 1996 Mercedes C280 will occassionally lose acceleration, pick back up, and lose it again
Unfortunately, my mechanic cannot reproduce the problem. I will be driving at normal speed. I stop for a stop sign or light, and when I accelerate it tops out at maybe 20 mph and then slows down to 5-10 mph, speeds ups to 20 mph, etc. The accelerator is held at a constant depression. If I put the car in Neutral, the engine cycles through the same loss and pickup of power. If I stop the car, and let it sit for a few minutes, it typically does not reoccur on that trip. It is not easily repeatable, but the 3-times it has happend to me seem to have the same pattern: I drive the car for about 30', I park for about 15' (i.e., the engine is still warm), I start driving again and it occurs. I have had several refills between incidents so I don't think it is bad fuel. My mechanic's only guess is the fuel pump, but they are hesitant to replace it without knowing for sure due to the expense. I am trying to get the problem to occur again so that I can drive it (slowly!) to the mechanic to experience it first hand. Thanks for any ideas.
A bit more info. My mechanic actually identified several other possible culprits including the Mass Airflow sensor, but without knowing did not want to just start replacing parts willi-nillie. They had the car for this last week, tried to reproduce the problem, to no avail.
I would check the ECT (Engine coolant temperature) sensor. Also check of vacuum leaks. For some reason when my car had a vacuum leak it ran worse at times like you describe. When it was restarted at a temperature in between cold and operating temperature.
Thank you Andrew. I know my mechanic checked for vacuum leaks but he didn't mention the ECT as a possible culprit - I will mention this to him!
I would first get the codes read off the ecu, it should be throwing a code, and that would lead you in the right direction into solving the problem. It sound to me like you have a failing throttle actuator. These cars have a drive by wire set up. The accelerator pedal is not connected directly to the throttle body, but instead to a module that sends a signal to the computer which in turn controls the opening and closing of the throttle through an electric motor. It's all electrical and prone to failure.
I was unaware the car was throttle by wire. If so that is a definate possibility. Thanks Lorne
Hi Lorne, thank you. That is useful information that I was not aware of!
my 96 Mercedes i just bought is having this SAME problem, but this happens to me Once or Twice per week. i noticed either the ASR or ASD light comes on as soon as i stop at a light or stop sign, then i cant accelerate at all ,if so hardly. I Read that the ASR and ASD are Anti Skid protection by the cars CPU. I ALSO read that you can Remove or Disable it. and being i dont live in the heavy rain or snow it shouldnt matter... Does anyone know how i go about disabling the ASR/ASD?????
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