We have an 86 300E we just bought that has been sitting for two years. Changed the fuel pump and filter, drained the bad gas, changed the fuel pump relay, and checked all the fuses. At first it would start and run ok when cold and then start to stumble when throttle was increased. Plugs were changed and after a day of starting it up and letting it idle for a while while we checked out other stuff it started stumbling at idle and when cold. Today it hardly starts even when cold. Our first two Mercedes Benz were a 230C and a 250 so all this injection and electronics are new to us.

Hope somebody can offer some suggestions.

 

Hi billsfan60,

Have you tried to clean the engine idler? If it still persist Replace it...+ Clean up the throttle body as well