Tip auto box problem

[Steve Taxi]

Hi, my w reg c220 cdi w220 has recently developed a fault with its auto box, its ok when first setting off if I am gentle with it but as soon as I accelerate hard it starts to play up, after that it wont work right until switch it off and start again, heres the symptoms...from a standstill full throttle it changes up all 5 gears by the time its doing 40mph and wont change back down even at full throttle, also it reaches 80mph 3000rpm in top and wont go any more, it changes up and down the box manually ok but wont rev above 3k rpm, switch it off and its ok again until I floor it and the problem comes back, it wont kick down at all once its in top gear, heres hoping one of you techies will have seen this before or its a trip to the dealer, regards Steve.

 

[jberks]

I understand that if the diesels go into default mode, they won't rev above 3k.
It could be that your gearbox is fine and you have an engine management sensor fault.

 

[Steve Taxi]

Thanks just been reading some old posts and it might be the MAF sensor

 

[Steve Taxi]

Sorted...I just removed the MAF to clean it and found the air filter element had disintegrated and was blocking the ducting and obviously affecting the MAF readings, a genuine filter as well, theres a lesson if your gearbox is playing up check the air filter!!!! cheers Steve.

 

[MW]

How old was the filer? I have always thought that modern practice of high milage was in sharp contrast to 20-30 years ago when annual replacement was common. Can't think it a good idea.

 

[Steve Taxi]

The filter had been in for 50k miles 7 months, yes it should have been changed before this happened but it got forgotten, I assume it was blocked and the suction had pulled it apart.

 

[Newby]

I know you're sorted now, but if it helps anyone else, this problem is not confined to diesels. My S500 W220 did exactly the same and had to have a new air mass sensor. Cheers..... Brian

 

[tamrsoft]

Why not change the air filter when you do the oil/filter service, I do. They are cheap enough and will ensure maintained fuel efficiency as well as ensuring that expensive problems don't result from the type of failure described above (which could have damaged the MAF)