Panting Benz!

I have a 1999 Benz C280 Sport with 187k miles on it.

I have one problem I can not seem to find a solution to. When I am driving in the city and hit brakes at a stop light or such - the car pants! The rpm goes up and down around 5rpm. A few seconds later the car is back to normal. But when the car is panting if I try to accelerate the car hesitates for a couple of split seconds before resuming ride.

I have been to mechanic multiple times for it and the problem has not gone away. The recent visit he replaced the fuel pump (the car was hesitating and mileage had dropped bad). The panting problem is still there.

Please would be grateful for any tips or suggestions. I am trying to decide if its time to let the car go (sell or trade in) or its worth keeping it (I really like the car otherwise).

You have a leaking power brake booster. Remove and replace your mechanic before you do anything else. The mechanic should have keyed in on this problem within the first 10 seconds like I did.

The symptoms point to a leaking brake booster.
Any mechanic worth his salt should be able to diagnose this very easily.

Thank you missleman and VDCdriver. I will get brake booster checked and update on the progress. Really appreciate your insights. Thank you again.

Missleman, VDCDriver

You guys were right on the money. It was the brake booster! I would never have in a million years guess a deteriorating brake booster could cause the engine to rev erratically. Thank you both very much for taking time to help me out. You guys rock!