W204 MAF related limp mode

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Warrenfrs

New Member
Joined
Oct 27, 2020
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13
Location
Midlands
Car
Seat leon
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.
 
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.
Msl strikes again, sounds like lots of guess work to me considering they're calling themselves specialists lol when they replaced your cam cover more than likely they didn't store injectors upright as per working instructions of WIS. So injectors maybe able to be restored by actuating them. Have they done smoke test properly?
 
Msl strikes again, sounds like lots of guess work to me considering they're calling themselves specialists lol when they replaced your cam cover more than likely they didn't store injectors upright as per working instructions of WIS. So injectors maybe able to be restored by actuating them. Have they done smoke test properly?
I wouldn’t know re. the smoke test chap. Tbh msl have looked after the car for the last 40k miles and I’ve had no issues with them, so I would assume it was performed correctly.

I really just want the car running correctly again!
 
I wouldn’t know re. the smoke test chap. Tbh msl have looked after the car for the last 40k miles and I’ve had no issues with them, so I would assume it was performed correctly.

I really just want the car running correctly again!
Yeah but doing servicing for 40k miles any muppet can do, well if the wiring to the air mass sensor checks out, egr and vacuum system work as it should then I can only see the air mass sensor being at fault
 
Surely air box is upstream from the MAF?If that wasn't sealing you'll get unfiltered air, but it would still pass through the MAF. Leaks downstream of the MAF are a problem.

What's the relationship between a rocker cover and a boost leak?
 
Does anyone happen to know what the airflow rate should be on a functioning car?
 
Something I posted on the other forum

You can calculate an approx figure

Volume of theoretical air per second in cm3 is

Cyl vol[cm3] x RPM x no. of cyl/ (2 x 60)

Convert that volume to a mass assuming

Density of air @15degC in g/cm3 is 1.225 x10^-3

For a 2 litre at 800 rpm

500 x 800 x 4 / (2 x 60) = 13333.33 cm3/s

Multiply by density

1.225 x 10^-3 x 133333.33 = 16.33 g/s

That's theoretical, so assuming the engine has a volumetric efficiency of 90% gives

16.33 x 0.9 = 14.7 g/s

EGR will reduce this. So if active maybe reduce this by upto 50%.
You really need to make sure EGR is closed when checking.

This works when you have no boost, so idle or high idle.
 
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Yeah but doing servicing for 40k miles any muppet can do, well if the wiring to the air mass sensor checks out, egr and vacuum system work as it should then I can only see the air mass sensor being at fault
New unit from Merc fitted, and no change. So it’s definitely not the sensor unfortunately.
 
New unit from Merc fitted, and no change. So it’s definitely not the sensor unfortunately.
Have you reset adaptions via xentry or a scanner that has that function?
 

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