Engine not accelerating past 40mph

[Oteda]

I was driving quite casually for a while in my W221, and then when I finally got some space I decided to accelerate at around the 40 mark and noticed no power was felt, the rev meter almost stayed at 2 revs if not lower and the car slowly accelerated. I even put my foot down to the floor and this made no difference. Tried it in manual, same thing.

Parked up and switched the engine off, after a while I started again and the problem had disappeared. Accelerating as normal. Any idea what it could be? I have a health check booked in next week and will see to it then, at the mo its driving fine.

 

[Harrythedog]

You've gone into limp mode. Switching the engine off then on again sometime resets the problem. Could be a number of things causing this and a STAR diagnosis will determine what it is.

 

[Deleted member 37751]

Sounds like the MAF.

 

[Oteda]

So thats limp mode, thanks a lot. I did some research on signs and symptoms of a faulty MAF, and it does seem like that is what it is. My car hesitates to accelerate by about 2 seconds, and sometimes I feel a slight chug at 40mph. I have a health check up at Merc on saturday I will look into all of this. Anybody know a good mechanic in London who can just clean it for me would be appreciated.

 

[ucr]

Must be the cheapest S Class in the world to run

 

[artyman]

Silly question, but had you activated the speed limiter by mistake.

 

[hestonmob]

had a similar problem with my c240 just wouldn't respond. it turned out to be the air mass sensor.

 

[Oteda]

No I hadn't. But I do believe it is the air mass sensor. My car was parked up for a while before I bought it and since the incident I gave it a good blast and its running better. I will look into getting the MAF cleaned and hopefully not replaced. Thanks for all your help guys.

 

[cuprastu]

Another vote for the maf sensor, my car wouldn't go above 80, nor accelerate from a standing start very well, cleaned maf and everything back to normal, in fact the idle was smoother after cleaning.

 

[BlackC55]

Your best bet is to get it plugged in first. I take it its a diesel? If it is I doubt a MAF fault as they are fairly relaible.

Inlet port shut off is my guess.