hesitation when accelerating 97e320
 

hi there, i have been experiencing some strange behaviour from my 97 e320, it only has 65000 km on it. when cruising and then trying to accelerate hard, for instance going to wide open throttle when merging, the car seems to lose power as the revs approach 4000, and then right at 4000 there is a hesitation that almost feels like hitting a rev limiter. the acceleration tails off before this occurs, almost like the throttle is only 1/3 way open instead of wide open. if i accelerate from a standstill, the engine will rev to red line, but there is a loss of power. the car is very low mileage and has been babied... major service was performed a couple years ago, but the car has only been driven about 15000 km since then, if that. (under 10k miles). does anyone have any idea what the problem might be? the engine feels completely normal in everday driving shifting at 3000rpm and below, no loss of power or anything.

bump

Does this happen in consistently the same gear? Do the problems you describe, for example, always happen under full throttle in second gear and first is fine, or does it not matter what gear the car is in?

Sounds like a classic Air Mass Meter failure. I bet if you run adaptation values for fuel trim the compensation will be over 1.10...

Check your plugs - make sure they are F8DC4 Bosch and that they are gapped to 0.032". The engine will misfire on heavy load if the plugs are not right and they are old (increased gap due to electrode wear). Just went through a similar episode with my '94 wagon.

It's the AMM, get a new one. I went through this a few weeks ago. While you're in there, take out your airbox assy and ducting, scrub it, let it dry, put it back together, and change your air filter. Good as new.

Phil @ fastlane got me one in a day.

hi there, thank you for the replies. it does seem to only happen under wide open throttle, and often seems to be when u floor the accelerator and the transmission shifts down 2 or more gears. say if i was merging onto a highway from 35mph and then wanted to accelerate hard up to 70mph. the spark plugs were changed 2 years ago by the benz dealer, and ive only driven about 10 000 miles since then. should they still be ok? how much is a air mass meter? is it difficult to replace on your own? would anyone be able to direct me to a place where i could see instructions on the procedure? there is no check engine light, and if u keep the throttle at 3/4 the engine will rev up fine. thank you again.

Like they said it is probably an air mass meter. It is easier to change than the air filter.