My 2012 c250 sedan started to lose power, seems like going into limp mode here and there (after 1st gear or so, would be very sluggish). Can has 135k miles and well taken care of. Lately there have been a number of problems, last one was a thermostat issue that we just fixed 2 months ago, which followed a coolant leak that we also got plugged. Then there was a exhaust gas leak about 5 months ago that ended up getting into the car cabin via the air conditioning. These were all fixed by the dealer.

Took it to the dealer, they claim the turbo needs replacement (>$5k), without guarantee that this will fix it. Asked for the code and was told the diagnostic code was 29291, but that does not sound to me like any code I've seen before. Looked around and nothing comes up.

Dealer claims the turbo is not generating pressure and needs to be replaced. Note that there was also a very strong gasoline smell, I've read elsewhere that it could be the high pressure fuel pump.

Been talking to an independent shop which says they think this is very rare to have the turbo changed, and they suspect something else is at play, but can't tell unless they look at it.

I'm. torn between trashing the car (quoted turbo repair probably puts it at par with kbb value and may not be worth it), or towing it to the independent shop for an eval.

Any thoughts?

 

I'm not an expert with the M271EVO (250) engine, but from what I've read online, the car going into limp mode usually comes down to the high pressure fuel pump.
Now in all cases, you need to get the car properly scanned to have all the codes analyzed and then we'll know for sure.

This engine suffers from 3 common problems if you research the forum here: high pressure fuel pump failure, timing chain stretching, and turbo failure.

Do some more research and see if you can relate the symptoms you're facing with the posts here.

 

Thanks, that's what I expected from other searches, that the most likely item was the high pressure fuel pump, and was rather surprised to hear from the dealer about the turbo. Thanks for listing the most common problems, I think the timing chain was changed a while back for a major service, but I'll check with the records. I'm afraid that if we fix the turbo, the high pressure fuel pump will be the very next repair.
Personally, I'm thinking this is hardly worth it, the kbb value in good condition is virtually the same as the quoted turbo repair.

Thanks for the feedback.

 

I think you misheard the code or they got it wrong - perhaps they meant P029921?

If so that is a boost error code, and you should first check the turbo intake pipe for cracks and also the blowoff valve for correct operation. I would rule both of those out as they're inexpensive compared to a turbo replacement. It sounds like you need to take it to a MB specialist shop rather than a dealer. Someone needs to actually diagnose this rather than the dealer just wanting to throw parts at it at your (significant) expense.

Part number for blowoff valve: 000-153-11-59