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Pete, Mercedes Mechanic
Category: Mercedes
Satisfied Customers: 29113
Experience:  Over 15 years experience as a Mercedes dealer technician
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I have a 1995 S420 runs 20 minutes and

Customer Question

I have a 1995 S420 runs for about 20 minutes and sputters out as if its loosing fuel. I've replaced plugs, wires, engine wiring harness, fuel pressure reg., throttle position sensor, crank position sensor, fuel and fuel pump. I was told that this type of vehicle has a type of (engine shut-down) sensor that will auto shut the engine down if the "thermostat" is bad. Is this true and/or where do you believe the problem could be?
Submitted: 1 year ago.
Category: Mercedes
Expert:  Pete replied 1 year ago.

Hi my name is ***** ***** I will be happy to assist with this today.In some cases I may need more info to assist better.I apologize for any delay.

If you have a failing mass air flow sensor this can act up after a bit of time of running as I have seen before on this model here and can send an incorrect air flow reading signal and cause this issue here.I had a problem one of these S classes around this year that did the same thing and spent weeks trying to locate the fault and then swapped in a new mass air flow sensor as I was out of ideas and it corrected the fault here.

If more help is needed, use the reply tab to continue our conversation. If no further assistance is needed, kindly rate my service.You can rate at any time and we can continue to work on your question as this will not close out your question.Keep in mind in some cases it can be difficult to fully diagnose or help repair your vehicle without seeing it and I work on delivering the best possible answer from what I see to work with.

Thanks Pete