ML 270 kick down not working

[Farsight]

Have a 2001 ML 270 - recently started losing power when driving to point where can only slowly get 2000rpm from it. Kick down doesn't work etc. Seems to correct itself when cold but soon reappears - dealer is absolutely no help except a big bill for plugging in diagnostics as problem persists
Any suggests would be gratefully accepted

 

[jberks]

1) forget the dealer
2) Find a good indie and let them sort it.
Loss of power could be anything, from the turbo to a sensor. The diagnostic should have shown something. Did they say anything?

 

[Carvoeiro]

The most likely cause is the air mass sensor. Has this been replaced ?
If no, get it done and it should solve the problem.
If yes, you need to check your exhaust for restriction

 

[Carvoeiro]

There is a lot of detail about the air mass sensor at:

http://forums.mbnz.org/forums/

 

[jberks]

I agree that the MAS is a strong contender. I've replaced one myself after similar problems, but it can also be wastegate, cat, loose turbo pipe etc. The point is that the MAS is quite expensive and it may not help. I've always felt that a proper diagnostic and fault code extraction is the best way with these things, (with the exception of the brake light switch as its only a tenner). Otherwise, you're as well putting £150 on red - you may hit it right, or you may lose your money and end up forking out for a diag anyway.
However in this case, the dealer has done a diagnostic, only as it was 10 days ago and Farsight hasn't come back with the codes so I assume he's sorted.

 

[Carvoeiro]

My car is a 2001 CDI270. with now 150k km.
It started , as usual , that the engine would loose power and no kick down, no gear change.I did all what needed to be done i.e. replace the air mass sensor, change the air filter etc. However the problem continued. The only thing which helped was to stop the engine and restart. Than I started to have a 'hissing' noise coming from the rear when accelerating after having stopped and restarted the engine, mainly when going uphill. Checked for air and fuel line leaks, nothing found.

And the low power problem got worst. It happened now also at low speed. I just needed to go a bit uphill and promply there was the power loss. Each time the only way to continue to drive was stop and restart.

All this made me thinking that the problem might be not on the intake side of the engine but at the exhaust. I did notice that a slight rattle came from the middle exhaust pot. I decided to cut the exhaust open and sure enough, there I found the exhaust filter was completely loose in the pot. The filter has the shape of a approx. 5 inch diam ball and made of some very light fiber material. The filter itself looked very clean, almost like new but there were several round marks with the diameter of the exhaust pipe. You are already guessing what happened. The filter ball was floating around in the pot and ocasionally blocked off the the exhaust outlet causing restriction to the exhaust gas flow (and the hissing noise). Therefore when stopping the engine, the ball would drop down and the engine would run for a while until the next time the ball would get again in the way of the exhaust gas flow. So I decided to throw away that filter ball and welded the pot together again. Now the car goes like a rocket and no more power losses.
I got a bit concerned with the consequences of the MOT inspection but recently the inspection did not reveal any increase in emissions. The emission of the car are treated by the cat which is just after the turbo. The filter in the middle pot is just an additional filter which really has not done anything, just trouble.