im new here so first off i would like to say hi to you all
i have a 2000 ml 270 cdi
it loses power very intermitantly and will not rev above 3000rpm(seems like get home safe mode)this mainly happens going up any kind of gradiant.if i turn ignition off and restart engine it will be fine for a while .i have read as many threads as i can find on this and they all seem to point to the maf. so i changed this and the problem still persists. i changed it again for a pierburgh one that was fitted originally by merc.however this problem still persists.im sure some one out there must have the answer please please help it drivin me crazy
br
ml270
ps i have also had it on diagnostics but it shows nothing to be at fault

 

I had a similar issue with my ML270. It happened rarely, but was very frustrating when it did. On the diagnostic front I found an error related to the inlet port flap position. By way of explanation, many of the CDI engines have "flaps" - like butterfly valves in the inlet manifolds. The purpose is to promote swirling of the air-charge to the cylinders and improve combustion.
On the 270CDI, these flaps are connected together by a rod, which is actuated by a motor at one end- with feedback to the CDI ECU. The flaps and the actuating rod are right underneath the inlet manifold -in front of and about 6 inches above the starter motor. A more inacessible place you can barely imagine. Anyway, the flaps are attached to the actuating rod by ball/socket connections -whch can become slack. In my case the rod had become un-plugged from the front 2 flaps and was sitting off -line a bit. This was important because there is not enough clearance for the rod to operate it's full stroke - it butts up against another fitting/bracket. That screws up what the ECU set up for the appropriate fuel mixture/engine loading. Your car feels gutless. I found if you re-started sometimes the actuating rod would clear the bracket and everything would be well.
If you want to have a good look, jack up on the NSF, remove the wheel, then take off the inner wing plastic shield (watch the clip out of sight near the sill)
Get a good light and a mirror and look up underneath the inlet manifold.
Whatever you do with the flaps, be gentle. You can just stretch a hand up there to plug the flaps back into the rod. Check the other (rear) end of the rod is attached to the actuating motor (above/ in front of the starter) There is a dog-leg lever connection here. I had nothing actually broken, just loose and un-plugged.
If you break anything permanently - you will probably need a new inlet manifold. (about £600 I think - no parts available separately ) and a huge amount of dismantling to replace it. I've a copy of WIS which explains most of the function & procedures. See attached screenshot -may explain the layout. Let us know what you find.

Regards, Graeme