i have a 1999 clk320.when driving slowly everything is ok.as soon as you open the throttle the car does not want to know,it coughs and splutters and has a lack of power.pull over,apply the brake and it feels like it wants to stall.switch the car off and back on and all goes back to normal,until you press hard on the gas.took car to local dealer and they told me the 2 o2 sensors needed replacing which they went ahead and did.unfortunatly the same problem exists.can anybody please help and shed some light on the problem....

 

the first 3 things that come to mind are..sounds like airmass or clogged cats or bad gas.

 

the car is still in the specialists.they tell me no fault code are showing,just the message left bank shut down.they have checked the cats and seem to be fine.i think they did an air mass test.will check tomorrow.bad gas seems interesting.checked the web and found hundreds of cases.the symptoms people sufffered seem very similar to mine.what is the easiest way to check for bad gas.will check with specialists tomorrow to see if they have gone down this route.thanks very much.