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His is a later model, 260bhp. Apparently whilst a twin turbo version is mooted in the internet I cannot confirm it's existence.
Seems bonkers to have two air filters and two MAFs when you've only got one turbo though.
I did read an article that said at low load they throttle one intake more than the other to increase turbulence. If @doomanic was measuring at idle this might be what he's seeing.
That was at idle.
https://www.google.co.uk/aclk?sa=l&ai=DChcSEwjznKrqvfn9AhWQrdUKHb1wDrwYABBNGgJ3cw&sig=AOD64_0PHoSX949QMSfEisFS0lXDeNRn1w&adurl&ctype=5&ved=0CAIQz7YHKCZqFwoTCIDb1Iu--f0CFQAAAAAdAAAAABA M" alt="om642" />
How the hell did you try to post that image? 🙂
MAF readings are still wildly different when driving. Time to get the spanners out and locate a part number.
Even at speed or hard throttle? Very interesting.
I recommend Autodoc for CLS parts and compare with Mercedes. Euro Car parts don't have much for this car, and GSF are a bit rubbish. Autodoc will take a few days to post though. And the usual advice, don't by cheapo knock-off parts. Looks like OEM MAFs are made by Bosch, Pieburg or Hitachi, but sometimes the aftermarket same branded ones are either slightly different the actual ones suppled to the manufacturer, so check Merc first - I reckon it's worth a small premium for slightly higher peace of mind - but perhaps not a large premium!
Also you could try a clean first with MAF cleaner. Spray only though don't touch anything.
I dunno if this has already been suggested but ....
Turn the aircon off ??? it's really bloody thirsty in my old Mondeo
Or if it a MAF issue or an air filter issue.
I’d repeat the test on the driveway with both air filters out or swap the 2 filters with each other, see if the MAF readings equalise (filters out) or swap, or stay the same.
Might also be worth trying some EGR cleaner spray, it should clean the MAFs too
Wynn's Diesel EGR Cleaner Spray Cleans Air Intake MAF Sensor Inlet Valves & Turbo https://amzn.eu/d/gz2viHo
I have bought some MAF cleaner spray for mine, just to see. I think they get dirty over time. When you think about how they work, it's clear that a slow accumulation of crud would gradually affect readings slightly year after year.
One thread I read suggested that the OP's engine and car are particularly susceptible to dirty air filters for some reason - not sure how that would vary by car but that's what was said. Air filters would have to be hugely clogged to make that much of a difference though, I'd have thought.
I cleaned my MAF. The difference is amazing..
..ly small. As you'd expect. It has made it slightly smoother I think, and it has affected the gear changes. When the car changes gear it has to adjust the throttle exactly to create a smooth change and if the sensors are slightly out the torque might not quite be what it's expecting so it gets slightly jerky or the transmission slows the changes down to avoid the jerk. Shifts were better after cleaning and with less of no break in power delivery.
No worries mate, here’s a post I did with loads of setup info etc on a Vito Facebook group
Cheers for that group link, they seem a knowledgeable and helpful bunch.
Hadn't realised yours is a 447, mines a face lift 639. App works well with my old elm scanner but doesn't give any dpf info, I'll have a play with the settings and see what happens.
Just a heads up to the OP and anyone on here who has a similar year, Mercedes C, E, or CLS.
Mine went in for its MOT last week and failed as the rear sub frame was corroded both sides, this is a warranty issue as an anti corrosion coating was incorrectly applied by Mercedes, the corrosion guarantee is twenty years so I'd get checking your rear sub frames as they'll go at some point. Mercedes are fixing these ( and mine) free of charge as it's a recognised common issue but I may be waiting for some time as the part is on back order, so carless for a while as Mercedes won't supply a courtesy car except when it's actually in for repair.
Yes, I read about this a couple of weeks ago. It has been serviced by a Merc specialist twice now, and looked at briefly by me, and mine doesn't look bad. But yeah it's not well publicised so good shout.
I don't suppose you have a pic of what to look for do you? Some garages send you pics.
What years are affected?
The garage I had my car serviced and MOTd at ( Stuttgart in Ponty) send their MOTs to the local KwikFit who said the rear sub frame was corroded and had holes both sides, so I took it to Mercedes Cardiff Gate and they inspected and photographed it and got back to me saying they'd repair free of charge ( £2K otherwise), although it was also looked at at the garage I bought it from who, unsurprisingly, said it wasn't too bad.
I don't have any pics unfortunately, Stuttgart said Mercedes will only repair when it reaches the point where it fails an MOT but I'd keep an eye on it, it'll go at some point.
Doomanic Mk2 CLS ran from 2011-2018, it also affects similar year E and C class models.
Hm, I live within walking distance of the Cardiff Gate place, I might ask them to take a look.
(may not apply but when cleaning MAFs, make sure you actually clean the maf. Lots of times people will spray around the housing or whatever but the actual key part is sometimes quite tucked away. I suspect of people who've cleaned it on my car, probably about half totally missed it)
I sprayed into the hole in the white plastic piece in the middle of the airflow. Looks like a Venturi effect sucking air into a little channel with the actual sensor in it.
The quality of the Bluetooth adapter can make a difference. I’ve got a cheap Ebay ELM one and it doesn’t play well with the app.
It’s still the same engine in the 447 as the 639, not sure if the electronics have changed though.
I've had the engine cover off today so I have a part number to search for. Yay.
The prices seem to range from €88 for a LÖWE from Germany to £250 for a MEAT & DORIA from Autodoc.
A complete batwing is £900...
Or £178 on eBay...
The nearside MAF and surrounding area is covered in dirt and oil, while the offside is clean. As the dipstick is right there it's possible it's spill from the last oil change. I'd post a pic if the forum wasn't so effing ackward.
Hmm, a possible source of contamination.
I tried to search for a sensor for your car on Autodoc, but it didn't come up with a brand I recognised for the car.
Definitely give Merc a ring and ask for their price.
Here's the Bosch part number; 0281002955
I’d post a pic if the forum wasn’t so effing ackward.
I can post it if you WhatsApp it too me.
Check your PCV diaphragm, they do go hard and could be the reason for the gunk
https://forums.mbclub.co.uk/threads/w211-om642-turbo-intake.260524/
Its on the other side of the engine. PCV is offside up near the front shock mount .
Worth checking as failure leads to even more crankcase gas going through the turbine and intercooler.
You need 4 x flat blades, like a junior haksaw blade to lift the tongues over the wedges and it pops open
This is also a reason for the earlier than recommend air filters change. Blocked filter will cause more neg pressure and potentialy increase the pcv blow by.
20 min job to remove, clean, replace.
Looking at those mafs, it appears they are individually replacable. But im not 100% sure, as there's 5 years between ours they might have changed the batwing desigb do the electrics can be removed
The pictures of parts on Autodoc look like they are individual components not integral to the batwing.
They are available to buy separately, just not sure how easy they are to remove from the flexible fitting. I had a brief try yesterday and they seem seem pretty firmly attached and there doesn't appear to be a clamp to undo.
Hm, strange, on mine the MAF housing is bolted to the air filter box and there's a jubilee clip holding on the hose that goes to the turbo. Apparently not on yours though:
If I were you I'd remove the batwing, spray loads of MAF cleaner in the hole in the sensor itself then refit and hope. Also, given the potential cost, you need to find out what the normal readings should be. However, if they both go into the same turbo, then there's no way they should be different as far as I can see.
If they are available separately there ought to be a way to remove. I'd probably do what that guy does and have a go at it. If you break it, then you still need a new batwing anyway.
The air filters are different. One has a black plastic matrix and blanked off area. Christ knows why. Emissions or to create a suction, turbulence, or some other reason
Hmm, I see. I read that each bank could throttle differently to create more turbulence, but then I assumed that didn't apply since I thought each cylinder bank would have its own throttle body.
But if the air filters are different, to add turbulence upstream of the combined airflow, then that's different. That said it seems weird to do that before the turbo as it's hard to imagine how the flow characteristics would be preserved after having been mashed through a turbo - but I guess they know better than I do 🙂
That said, if it's useful, why doesn't every car have two filters? Mine has two ducts at the front, just one is blanked off.
I haven’t read the whole thread so forgive me if this has been covered but have you checked the brakes. A slightly dragging brake will kill your fuel economy. Take it for a run then coast to a stop and feel the callipers and alloys for any excessive heat generated. Can you get the wheels off the ground and check to see how freely they are turning?
I haven’t read the whole thread
I haven't read your whole post, but unless it's something about MAFs it was probably covered in my first post...
Any update....... I'm intrigued!
No updates just yet. I was hoping to get a comparison reading from another 350D but unfortunately the owner's page on FB didn't offer up any volunteers.