Running lean p0171 p0174
Thread Starter
Junior Member
Joined: Dec 2020
Posts: 53
Likes: 4
From: Oslo, Norway
W212 E350, W208 CLK320
Running lean p0171 p0174
Hello
I have a 2009 w212 E350.
This weekend the check engine light started illuminating and when I checked the codes I got P0171 (system too lean bank1) and P0174 (system too lean bank 2). I also got P2000 on another app. Went to two mechanics I know and one said it most probably was the lambda sensor (oxygen sensor) and the other said it could be build up of carbon or bad fuel causing it, and deleted the codes and told me to come back if the engine light comes back on. The only thing I have noticed is that when I drive at higher speeds and when the RPM is around 1500 to 2000, sometimes the RPM is a little choppy. Barely noticeable, but you can see the RPM gauge jump a tiny bit up and down. My car has been like this way before the check engine light came on. What are your thoughts about this? Where should I start?
I have a 2009 w212 E350.
This weekend the check engine light started illuminating and when I checked the codes I got P0171 (system too lean bank1) and P0174 (system too lean bank 2). I also got P2000 on another app. Went to two mechanics I know and one said it most probably was the lambda sensor (oxygen sensor) and the other said it could be build up of carbon or bad fuel causing it, and deleted the codes and told me to come back if the engine light comes back on. The only thing I have noticed is that when I drive at higher speeds and when the RPM is around 1500 to 2000, sometimes the RPM is a little choppy. Barely noticeable, but you can see the RPM gauge jump a tiny bit up and down. My car has been like this way before the check engine light came on. What are your thoughts about this? Where should I start?
Last edited by Andreas B; Mar 6, 2023 at 08:59 AM.
Thread Starter
Junior Member
Joined: Dec 2020
Posts: 53
Likes: 4
From: Oslo, Norway
W212 E350, W208 CLK320
It has not come back yet. I have not been driving much since I was there earlier. Will post here if the check engine light come back on. If anyone has any ideas about the RPM while driving at higher speeds it will be highly appreciated!
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Joined: Apr 2019
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From: Silicon Valley
W212 MY'14 M276-3.5NA @75kMi
both banks LEAN...
This is something comon to both banks at the same time, so not the pair of primary O2/Lambda sensors!
Take a look at your fuel pressure values. Is the pressure smooth regardless of demand or does it drop under load? Suspect pump and filter according to findings.
What is your current odometer?
Take a look at your fuel pressure values. Is the pressure smooth regardless of demand or does it drop under load? Suspect pump and filter according to findings.
What is your current odometer?
Last edited by CaliBenzDriver; Mar 6, 2023 at 03:02 PM.
Out Of Control!!
Joined: Apr 2019
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From: Silicon Valley
W212 MY'14 M276-3.5NA @75kMi
Easy does K.I.S.S....
- >
The low pressure pump is known to be questionable at feeding volume to HPFP. Needless to say, I am not familiar with your M272 engine! In particular: does it uses a 3-Phase PWM low pressure Pump.
Pressure must remain nearly stable and not fall flat down under acceleration demand.
Triple check the low pressure supply before suspecting $4k HPFP.
+++ never say never !!
There are M272 CGI engine after 2006...
Last edited by CaliBenzDriver; Mar 6, 2023 at 08:35 PM. Reason: directly injected past '06
Thread Starter
Junior Member
Joined: Dec 2020
Posts: 53
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From: Oslo, Norway
W212 E350, W208 CLK320
Well, it came back. Then I got a message on the display to check oil level. It was at the minimum mark! Filled it up and the light disappeared. Now I got a major leak somewhere, but my garage floor is dry and I don't smell any burnt oil or see excessive smoke from the tailpipe. I checked a little and it could be a common problem with the M272; Bad PCV and/or Cam plugs. I've also read that the P0171 and P0174 codes could come from a bad PCV. I already have the parts, and I tried to change them myself, but damn it is waaaay too little space to work there. When I watched a couple of DIY videos on YouTube on the same engine, they had way more room to navigate around than on my engine, and they had no problem what so ever to get to the parts and change them. Why is that? Being the same engine and all.. Also, they had their dipstick in the front of the engine while mine is in the back. A little clumsy place to have it but ok..
Last edited by Andreas B; Mar 31, 2023 at 08:18 AM.
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From: MA
2008 E350 4Matic, 2011 E350 4matic
So did you change both the breather cover and the oil separator? Yeah, there's just less room on the W212, you just have to use shorter sockets to get at everything. It was probably the excess oil going out the oil separator/breather cover. Or you have an oil pan leak. Because of the cover, you might not notice it. Also check the 3 plugs in the back and the oil cooler next to the oil filter. Also would be good preventative maintenance to change the two upstream O2 sensors. You can also get a scanner and scan for pending codes, could be the intake manifold getting ready to go. That's what happens when you have a bad oil separator/breather cover, oil ends up getting on the flaps of the intake manifold and gums them up.
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Joined: Apr 2019
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From: Silicon Valley
W212 MY'14 M276-3.5NA @75kMi
vaporized oil coats O2/Lambda
Well, it came back. Then I got a message on the display to check oil level. It was at the minimum mark! Filled it up and the light disappeared. Now I got a major leak somewhere, but my garage floor is dry and I don't smell any burnt oil or see excessive smoke from the tailpipe. I checked a little and it could be a common problem with the M272; Bad PCV and/or Cam plugs. I've also read that the P0171 and P0174 codes could come from a bad PCV. I already have the parts, and I tried to change them myself, but damn it is waaaay too little space to work there. When I watched a couple of DIY videos on YouTube on the same engine, they had way more room to navigate around than on my engine, and they had no problem what so ever to get to the parts and change them. Why is that? Being the same engine and all.. Also, they had their dipstick in the front of the engine while mine is in the back. A little clumsy place to have it but ok..
Oil gets flash vaporized by the burning hot cylinder walls.
I bet your engine features the "managed oil pump" solenoid design... Below 3500rpm the cylinders are purposely not sprayed to "save gasoline".
Go ahead and remove the intake plenum to get more engine top access and empty the oil out. Plenum is part of the oil separation and storage...
Even a new PCV kit may not help the oil consumption issue.
Engine drinks quarts from factory new condition. At later mileage you get more blow-by from worn out cylinders and stuck rings, carbon deposits.
> Adding up... 1+2
You can suspect contaminated O2/Lambda sensors. The carbon residues from the burnt oil plug up the exhaust sensors. They become unable to snif your combustion gases...
Therefore replace "upstream only on both bank 1+2" to help your engine recover some responsiveness
What engine oil are you using currently ? ?
Last edited by CaliBenzDriver; Apr 1, 2023 at 07:19 PM.
Thread Starter
Junior Member
Joined: Dec 2020
Posts: 53
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From: Oslo, Norway
W212 E350, W208 CLK320
Thanks for answers. I just cannot change the parts myself, it is too freaking tight. Ended up bleeding on my right hand because it scratched against the firewall all the time. The oil I am using is 5W-30. I am going to need help to change the parts and I will consider changing the 02 sensors too.
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Joined: Feb 2014
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From: MA
2008 E350 4Matic, 2011 E350 4matic
Thanks for answers. I just cannot change the parts myself, it is too freaking tight. Ended up bleeding on my right hand because it scratched against the firewall all the time. The oil I am using is 5W-30. I am going to need help to change the parts and I will consider changing the 02 sensors too.
Out Of Control!!
Joined: Apr 2019
Posts: 12,031
Likes: 6,841
From: Silicon Valley
W212 MY'14 M276-3.5NA @75kMi
Thanks for answers. I just cannot change the parts myself, it is too freaking tight. Ended up bleeding on my right hand because it scratched against the firewall all the time. The oil I am using is 5W-30. I am going to need help to change the parts and I will consider changing the 02 sensors too.
Last edited by CaliBenzDriver; Apr 3, 2023 at 02:41 PM.
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2008 E350 4Matic, 2011 E350 4matic
https://operatingfluids.mercedes-ben...sheet/229.5/en
Last edited by cetialpha5; Apr 4, 2023 at 04:45 AM.
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From: Silicon Valley
W212 MY'14 M276-3.5NA @75kMi
sticky oil
Technically if it's on the list, it should still be ok, depends on the environment. But Mobil 1 0w40 or Castrol 0w40 is usually pretty popular. Lots of times people grab random oil that's not 229.5.
https://operatingfluids.mercedes-ben...sheet/226.5/en
https://operatingfluids.mercedes-ben...sheet/226.5/en
Thinner W30 oil vaporizes faster out of crankcase
All good ... better than dry oil change
I am two finger away from thinking AMSOIL pure PAO base may be worth looking into... what about packages
AMSOIL heroes anyone?
Last edited by CaliBenzDriver; Apr 3, 2023 at 05:57 PM.
MBWorld Fanatic!
Joined: Feb 2014
Posts: 6,190
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From: MA
2008 E350 4Matic, 2011 E350 4matic
We can trust the MB oil spec... the furthest away from it, the worse the oil. Stick with compliance is not bad.
Thinner W30 oil vaporizes faster out of crankcase
All good ... better than dry oil change
I am two finger away from thinking AMSOIL pure PAO base may be worth looking into... what about packages
AMSOIL heroes anyone?
Thinner W30 oil vaporizes faster out of crankcase
All good ... better than dry oil change
I am two finger away from thinking AMSOIL pure PAO base may be worth looking into... what about packages
AMSOIL heroes anyone?
Thread Starter
Junior Member
Joined: Dec 2020
Posts: 53
Likes: 4
From: Oslo, Norway
W212 E350, W208 CLK320
So should I change the oil? I never had the problem with excess oil consumption until recently. I'm not an expert on engine oil, however I live in Norway where it can get very cold in the winter. Should I change to 5W40? I forgot to say that I use MOBIL 1 oil if that makes any difference. The car is running perfect: No weird smells, no rough idles, no excess smoke from the tailpipe, smooth driving both on highway and at slower speeds, feels responsive when I want it to. The only thing I have noticed is that when I kicked down the pedal once when driving at higher speeds (110km) I saw a good amount of exhaust from the tailpipe. I have a friend who literally has read Mercedes manuals as a kid and if he got the time I will get my car to his shop as soon as possible to change the PCV and CAM plugs, and also check oil cooler and the stuff you guys has written about. I appreciate your answers!
MBWorld Fanatic!
Joined: Feb 2014
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From: MA
2008 E350 4Matic, 2011 E350 4matic
How many miles on the oil? Mobil 1 does have a Mobil 1 FS 5w30 on the approved list. Others would not be. You just have to look on the back of the bottle and see what approvals the oil has. Should be a section that mentions Mercedes and it should say 229.5. If it doesn't, then it's not on the approved list and the only Mobil 1 5w30 on the approved list is Mobil 1 FS 5w30 and if that's not what you're using, it's not on the approved list. I would probably say if it's over 5k, then change it, between 2.5-5k, more of a toss up.
Out Of Control!!
Joined: Apr 2019
Posts: 12,031
Likes: 6,841
From: Silicon Valley
W212 MY'14 M276-3.5NA @75kMi
oil cloud issue....
.../...
The only thing I have noticed is that when I kicked down the pedal once when driving at higher speeds (110km) I saw a good amount of exhaust from the tailpipe.
I have a friend who literally has read Mercedes manuals as a kid and if he got the time I will get my car to his shop as soon as possible to change the PCV and CAM plugs, and also check oil cooler and the stuff you guys has written about. I appreciate your answers!
The only thing I have noticed is that when I kicked down the pedal once when driving at higher speeds (110km) I saw a good amount of exhaust from the tailpipe.
I have a friend who literally has read Mercedes manuals as a kid and if he got the time I will get my car to his shop as soon as possible to change the PCV and CAM plugs, and also check oil cooler and the stuff you guys has written about. I appreciate your answers!
PCV may help if it has failed.
Try switching thicker engine oil: 40 instead of 30.
