MAF related woes (not a Clio!)

[ForceIndia]

Car is a 2011 c220cdi estate, 140k miles. MSL remap and dpf delete. EML light came on a few weeks ago, drops into limp mode.

Took it into MSL, suspect a faulty MAF or air leak. Changed the MAF, no improvement, back to MSL for further diagnostics. Advised there's a rocker cover leak, and losing boost from here. Booked in for the rocker cover to be replaced, but the fault still remains.

Chap at MSL suggested the airbox could be the problem (possibly not sealing to the MAF sensor). They've also carried out a smoke test, and can find no leaks. I would of thought that the airbox suggestion would show on a smoke test?

Additionally, since collecting after the rocker cover was done, I now have 2 injector related codes showing on carsoft scanner (these have never come up before). So in total, 3 codes

P010100 Mass air flow sensor 1 has a malfunction
P0263C0- teach in of the operating parameters for cyl 1 has a malfunction
P0269C0- teach in of the operating parameters for cyl 3 has a malfunction

Data wise, wasn't sure if this temperature reading would be correct
B19/11 (Temp sensor upstream of turbocharger) -11 degrees C

Airflow rate from MAF is 16.21g/s at idle, rises to 94g/s @3k rpm (stationary)

Any suggestions as to what's going on would be much appreciated, or what to do next. Feels a bit whack a mole at the moment, changing parts in case they're the issue, rather than knowing what the issue is.

 

[G Hut]

May help i hope, I had a 2012 250CDI and light came on at 60k.... took garage ages to find as suspected the MAF but all was okay and showed leak. They had to get a smoke machine to pressure the intake and revealed a tiny hole burnt through on the plastic inlet manifold.... this turned out to be caused by broken mount stud. If I can find the thread on the merc forum i will post as seems few people have had this broken stud and burnt manifold issue. Manifold wasn't expensive as was subsidised by merc so clearly an issue as an indy did my work

 

[Bluebeard]

As above, may not be the issue but…

my dads current Merc was doing something very similar. Properly random MAF issue and subsequent EML and properly random limp mode. Absolutely no pattern and could go weeks without issue then it would act a t**t for a week solid. Then every other day. Then no problem for 5 days… you get the idea.

It was the loom that went to the MAF plug in the end! £40 to a local auto electrician and he’s never had the issue since.