I rarely work on diesels but since you said that your air filter was very dirty, I would remove the Mass Air Flow insert and spray clean it with CRC Mass Air Flow Cleaner. Not knowing where you are from, I do not know its' availability, but try and get this product, it works very well. If not use an electronics spray cleaner.Hi
I have a late 2003 ML270 CDI. The car drives fine and accelerates strongly from standing.
I have noticed however that at 70 mph cruising on the motorway if I accelerate gently I get a pulsing or surging acceleration. The rev counter echoes this pulsing by moving up and down.
This is not a violent pulse and up to that speed the car drives perfectly. I have changed the air filter thinking that may be causing it, and although extremely dirty the problem has not been fixed.
All thought appreciated.