I have a Benz C280,97 model,the problem recently, is that if u engage the gear  on drive,its an auto transmission,you have to rev the car to between 3000 to 4000 rpm before it shifts from gear 1 to gear 2.But after that it changes smoothly until u step on the brake and cycle continues again

Also when trying to speed up by pressing hard on the gas pedal,the car starts misfiring,by shooting from the exhaust.There is no rough idle,but i think the slow running is not good enough.

Then finally,it consumes fuel,but before these problems the fuel consumption is averagely ok,but now its excessive.

I have done the following,
Replacement of old plugs with new once eventhough they still ok.
Replacement of fuel filter
Replacement of transmission oil,but the transmission oil filter was not change,but the problems still persit.

Please i need you help all the gurus in the house.

Best regards.

You auto transmission might be skipping the first selection (1->2), and what you think is the first selection is actually 1->3. This would keep your engine at inefficient revs and cause the increased fuel consumption. So have someone take a look at your auto transmission system.

Its a Mercedes. You have to be very watchful so your mechanic does not make you spend so much on parts replacements. You should concentrate on checking first before buying.

One quick check here; when the car is in Park position and you step on the accelerator to rev. the car, does it misfire? (while in Park and stationary)

If it misfires - then

1. Check your idle control sensor (valve),
2. Check your air-intake sensor (Its the circuit thing on the air intake - big hose) - and very importantly, the air filter.
3. Dont let them talk you into changing any injector manifold - have them clean it thoroughly.

If you sort out the misfiring while the car is in Park and stationary, then you can test it while moving to see IF it shifts smoothly.

Please let us know how this works out; most importantly IF it misfires in Park.

@Onwan,when the car is park and i rev it up to 4000 rpm,it does not misfire.It only misfires when its on drive.

Thanks.

Sorry for the delayed response - Ive been in meetings.

It appears a fuel line/injector issue. I am assuming you do not have any smoke issues, but even with that you will need to have them service and clean through your injector - the whole injector assembly.

Also (Based on a recent discovery on nairaland.com); check the fuel hose line and your fuel pump for pressure. Please do this and let us know.

@Onwan, Thanks a lot onwan for your inputs,i will do as you suggest over the weekend and keep you informed .happy weekend.

Best Regards