E250 Cabriolet intermittent limp mode

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GFGF7292

New Member
Joined
Sep 17, 2020
Messages
1
Location
Northern Ireland
Car
E250cdi Cabriolet Sport 125
Hi guys, sorry for the long post but any help/tips/ideas would be appreciated.

My January 2012 E250 CDI has developed a rather annoying problem. After some time of driving the car suddenly loses kickdown/boost and will not rev over 3000RPM. There are no lights on the dash, and it builds speed very very slowly (right up to 90MPH) but there is no pull in the car whatsoever. Turn the ignition off, and on again and it pulls like a train until it starts to do the same again.
I took it to a Mercedes specialist who said it was the timing chain (was doing the dreaded 4 second tick on startup) so he replaced this at a cost of £900. Drove the car home and on the way it went into limp mode again. I turned it off, started and it drove fine the whole way home.
I took it to another guy (Ex Mercedes Tech) who plugged it onto the STAR machine, and it showed a vacuum leak and MAF sensor. The leak was coming from the water pump, so we replaced the water pump, MAF sensor and Air filter. No joy, the car is still doing this day and daily.

My guy said it is probably just a tiny pin hole vacuum leak, so he is bringing it back in next week..but any advice would be appreciated. This is so frustrating especially when I love the car so much.
Thanks in advance
 
I would ask him to do a smoke test to find the vacuum leak, he should have the gear to do it, MAF sensor as well he should be able to to replace with a known good one or read yours with STAR or other obd equipment, it may only need a clean with a proprietary MAF cleaner.
 

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