My 1997 S420, 70k miles, stalls when hot. Also will drop RPM on highway, but usually picks up and keeps running. Off highway will drop RPM and just die. Feathering the throttle helps some, but not always. Cruise control will catch falling RPM with a large jolt (seemingly not a good situation for transmission etc.). Recently replaced fuel pump relay for similar problem and intermittent no-start condition, worked for two weeks. New plugs and fuel filter at 60K. No engine codes at all.
The previous problem was motor would sometimes no-start, but frequently stall when warm (55-60C) such as after sitting for an hour, but would perform okay when fully hot. Now the stalling is when hot. Ran fuel injector cleaner/MB Carbon remover (no effect).
So far two dealers stumped. I suspect fuel pressure regulator.
The previous problem was motor would sometimes no-start, but frequently stall when warm (55-60C) such as after sitting for an hour, but would perform okay when fully hot. Now the stalling is when hot. Ran fuel injector cleaner/MB Carbon remover (no effect).
So far two dealers stumped. I suspect fuel pressure regulator.