Just took delivery of a 2000 CLK430 whose former owner apparently liked to drive it more than service it ( don't ask!). It has 40,000 miles. When sitting in traffic or at a stop light, it sometimes idles roughly and feels like it's going to stall. When the pedal is applied to accelerate, it stumbles and then runs fine. Air filters have just been replaced. At first, I thought it might be the fuel filer (which I'll change, anyway), but that should make things worse at higher speed and surely on hard accel (which it doesn't).

I'm guessing throttle body or MFS or...??

Any suggsetions?

Thanks,

Frank