Hi

Can someone please help me ? My ml 270 cdi 2003 has just started to loose power (sound familiar!) – but not all of the time. When you drive off in the morning the car works fine if you put your foot down you can feel the car accelerate and hear the turbo kick in with the engine revving past 4000 rpm. However, after about 20 min when the car has warmed up it suddenly looses power feeling very sluggish not revving beyond 2500 rpm even with your foot to the floor (like going into limp home mode but without a warning light). This makes it slow to go uphill or overtaking when you need the power.

I have been looking at similar problems that people have reported and come to the conclusion that it might be a faulty MAF sensor or possibly the fuel filter. I have tried unplugging the MAF sensor but this does not appear to make any difference.

Can someone please advise if I’m on the right track and should I try cleaning the MAF sensor with isopropanol or just replace it? If this fails what should I do next?

Any advice would be very much-appreciated

Thanks

 

Update:

After crawling home last night I decided to try cleaning the MAF sensor. I removed the MAF sensor (Pierburg A6110940048) from it’s housing and soaked the end of it in isopropyl alcohol for a few minutes (this released some dirty oily grime from the sensor) then sprayed the sensor with electrical contract cleaner, before replacing back in the car. I then took the car for a quick test drive around the block. The result was amazing the car felt like new the acceleration was much better than I can remember.

This morning I took the car on a 30 mile trip the power, acceleration, turbo performance was great to start with then after about 25 miles the power dropped off feeling sluggish not revving beyond 2500 rpm again.

Any ideas what to try next? Do you think the MAF is faulty and needs a more thorough clean or replacing? Or do you think that the MAF is nothing to do with the problem? Could it be the CAT? How would I tell? Could anyone explain to me if it is the cat why the problem is not there all of the time and why it does not effect the tick over (when the cat blocked on my E-class the engine would stall at tick over)? Someone suggested changing the fuel filter and or fuel pre-filters – where are the pre-filters?

Thanks

 

I have just replaced the mass air flow sensor then taken the car on a 6 mile test drive. What a difference the new sensor made - never had so much power! Who would have thought a small sensor would make such a difference!

 

ML430 I had both sensors replaced, spark plug wires replaced...the car runs fine then hit a bump and the car becomes non-responsive to the accelerator