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Haha, it's the fumes from to high fuel pressure. To my defence i only had the car for a brief amount of time.
It's the gdi version with the pump on the camshaft. I've seen the pump on my car with my eyes.
I think all blue efficiency car in eu has those.
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I think my last post is more sober. What do you think about the values for low and high side?
I do not have experience with Gen 1 GDI ur engine is using. That HP pump is crazy expensive at like Euro 3,000 ish.
M276 uses Gen 2 GDI, with simple cheap HP pump.
Your HP pump is similar to M271.8 , but you seems to be running a higher pressure than 120 BAR peak an M271.8 is using.
Looking at M276 GDI gen 2 fuel pressure strategy, I bet your Gen 1 is of the same strategy, at higher load, the pressure is reduced.
This pressure behaviour is not explained in WIS, I logged it all the time and I realized it is the strategy.
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I would look into your fuel hoses .......... and also your intake system for vacuum leak or flaps issue.
M272 intake system is fragile and kinda troublesome with age.
The flaps failure or partial failure can produce hiccups at speed.
.
Below fuel hose may kink and reduce flow.
Last edited by S-Prihadi; Jun 29, 2025 at 03:47 AM.
Would be lovely if someone could check the normal pressure values and how the regulator works. The regulator is very expensive as well. Looks lik a sensor with fuel going in it.
Still waiting on my smoke machine to check for vaccum leaks.
Will check fuel lines today.
Regarding the manifold I have the newer style with only one vacuum actuator and not much more. Does the flaps in those fail just as the old ones?
I have very little experience with M272 port fuel injection and its intake manifold system, only once I seen and mess with it, member's Tesna car.
But I know it is prone to breaking the flaps, usually the link from vacuum actuator to the internal flap.
If your is single flap , you must check if the flap is for lower rpm or the higher rpm one ?
If it is for low RPM, I would think your will suffer the same issue as M272 port injection low rpm flaps.
Low RPM flaps will work more than high RPM one for sure.
M272 should have smooth running monitoring...
You can use that while driving and see what's up with each cylinder behaviour.
By right if say the flap is the issue, all 6 cylinders would be effected.
If only a few cylinders seems out out of whack, you can shift your focus to component not shared by all 6 cylinders.
I will check the smooth running test and get back to you.
Don't know anything about the flap. Found very little info about this newer style setup. The only thing I know is that the vaccum actuator visually looks ok and I can feel the flap moving when I move the arm. This doesn't mean it is working though.
My smooth operation do not behave like in the video. It's all over the place for all cylinders. The are no cylinder that stand out tough. All are mostly around +/- 00,xx. Some times one individual goes -0,7 or up to 1,5. Did a couple of kickdowns. Saw numbers high as 8.xx but went away quickly and returning to bouncing around +/- 0,xx.
Checked fuel lines from tank to engine. No kinks or damage. Looks more or less like new. Everything fuel related on engine visually looks good. Waiting on smoke machine for vacuum hoses and service kit Inc spark plugs.
My smooth operation do not behave like in the video. It's all over the place for all cylinders. The are no cylinder that stand out tough. All are mostly around +/- 00,xx. Some times one individual goes -0,7 or up to 1,5. Did a couple of kickdowns. Saw numbers high as 8.xx but went away quickly and returning to bouncing around +/- 0,xx.
Non of the cylinders ever show 0.
What do you make of it?
There won't be a pure zero value, no way.
The value is acceleration of the crankshaft. So it is to be used best with maintained RPM and not while in kick down mode.
Find attached information on Smooth Running.
Well as document stated and you should read it slowly, anything above 3.0 meter per second is no good.
However DTC will only be registered when and if enough time/duration the instability occured and sometimes in more than 1 drive cycle.
They have their own logic.
M272 is still using older DAS software by the look of the interface, its data logging is not so good like M276 Xentry , but OK.
I think Xentry can do graph mode, easier to see the hill and valley.
See if you can find graph mode ?
Still have not done the smooth cylinder test. Checked fuel tank for dirt with inspection camera. Found nothing.
Smoke tested the vacuum system. No leaks. Did smoke test EVAP as well. Smoke gave trough around right rear wheel but that's just a vent I'm guessing.
Something I was thinking about, I wrote in my original post that when I disconnected the battery the car was fine for some time then the problem came back. About a week or so I disconnected the battery and the car has been fine. Like something freaks out after adaptation. What could it be?
The high rail pressure code is gone and have not come back.
I once had a drifted high pressure fuel sensor. At zero BAR it read 7 BAR.
No performance effect, I discovered it accidentally when depressurizing the fuel system and yet I am seeing 7 BAR.
No DTC.
Still have not been able to check anything but got a new code today " 0470 the effcieny of the nox storage catalytic converter bank 2 is not sufficient".
Does this help us anything? I think the Mercedes specialist replaced bank 2 nox sensor but I'm not totally sure.
Got new code today for nox sensor malfunction bank 2. Same bank as the catalyst code.
I can see high NOx value at bank 2 compared to bank 1.
Booked in at Mercedes to replace but they don't have time for another month. Let's hope the nox sensor cures the issue.
The high rail pressure code never came back.
Question, read in another thread someone saying our cars have wide band front O2. Is this correct? Voltage for my front O2 seams like narrow band being between 0.1-1v.
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