Dragonflyer

My wagon is 2008 R350 4Matic with 88k miles & serial number outside of balance shaft problems.

Symptoms: engine starts and runs smooth but surges when coming to a stop and throws P0016.

Preceding: timing chain replaced 18 months prior with new guides, chain tensioner & sensor wheels, balance shaft sprocket checked ok but the chain tensioner that came with the kit was probably not installed correctly resulting in rattling noise upon engine start. That rattle has gone away after I recently installed new tensioner but resulted in code P0016 generated as soon as engine warms up. I tried two new magnets and swapped all but one (behind the steering reservoir) cam sensors with the same and only code P0016 coming back (no P0017). With bank 1 intake magnet out, I tried actuating the VVT valve stem by hand and it felt smooth, same as the the valve on the opposite bank with which I was swapping the magnets. All sensor wheel marks (with exception of one behind steering reservoir which I din't want to remove at this time) are dead center at 40 degrees. I am using a generic code reader and do not have the ability to see DTC codes like 1208.

Asking for help before throwing more money at it.

Cheers!

PS: originally posted on W251 forum here

CaliBenzDriver

I went ahead and followed the link you have referenced.
I think your issue is a bad Intake VVT Phaser caused by worned out lock-pin.
This allows intake camshafts to get out of time with exhaust camshaft when oil pressure is minimal... hence correlation fault.

Go ahead and read this thread because I think you two share the same path.

Dragonflyer

Thanks CaliBenzDriver! Definitely will give it two full rotations while observing Bank 1 intake phaser.

Got further input from Mother Nature with all this rain and cold weather we've had in the South Bay and experienced a new condition this morning when starting cold: the engine surged from low, almost dying, to high idle a few times before settling into a normal idle and, once warmed up, threw out codes P0170 and P0173 relating to mixture being too lean, along with the now usual P0016. Hm...

Also thank you for leading me to the other member's thread with the Bidens in his ECM. Will be posting updates soon.

CaliBenzDriver

Okay, that's interesting condition. Perhaps you have a low fuel pump output or low alternator output in addition to your VVT Phasers being unlocked.

The other member has similar issue to your unlocked VVT Phaser in addition to tensioner and stretched long chain for Bank2 at driver side. Bank1 (cylinder 1,2,3) being on passenger side.

The rotation test can ve made super easy. No need to remove CPS! Simply rotate crank manually and listen for tic when VVT launches forward every two turns for each camshaft

Dragonflyer

Checked voltage with engine running: 13.5-14.3V and that's with cabin heat fan and heated seats on.

Dragonflyer

Had a chance to view all four phasers as I cranked and cranked and cranked and cranked and no, none of them skipped or behaved abnormally. All four dead center at 305 degrees and all four are secure. Installed four new magnets and sensors and, this time, got code P0017 thrown in addition to P0016. Engine surging upon decellerating is now even more pronounced and I am convinced it is the camshaft gear heads skipping. Question now is it only the two intake, since they are the only ones driven by a timing chain, or all four?

CaliBenzDriver

​​​​​​It looks like only intakes have VVT Phaser gear because your engine has only one long chain timing both banks. The exhausts camshafts are gear driven by the intake timing gears, not the intake camshafts.
Your ECU complains the position of exhaust relative to intake as seen by CPS is wrong. That i think means your intake VVT gears are floating around unlocked, at least one of the two.

Dragonflyer

Thanks CaliBenzDriver, I guess I referred to disks with timing circles, of which there are four, one for each camshaft. There is a VT valve at each camshaft, so theoretically, if one head is misbehaving, it is the Bank 1 intake. But if one is doing that, all four may be getting close, so I should replace all four?

CaliBenzDriver

The exhaust camshafts are gear driven by the intake...but their VVT Phasers are fully independent just as if driven by chain.

Let's recap troubleshooting, we know:

• the VVT pins are not unlocked : ok
• the CPS and solenoids : ok
• the tensioner, long chain, balance shaft : ok
• Alternator output : ok

That's a lot of good!
Then what else can cause correlation codes only at idle ???

If the VVT sensor ring was shifted it would at any RPM!

You've carefully tested the VVT circle marks are lined up giving us proof of perfect timing.

I just realize lining up the circles doe not test the worned lock pins. I still think based on your specifics, these VVT pins are your issue until tested perfectly.
This is tested by manually rotating crank AND observing VVT position slide forward 1/2 inch. Concentrate on Bank1 Intake VVT.
I am sure you can dig videos on that testing.

Today I have to deal with one of my own door lock module - So I am going to concentrate on that while you focus on "M272 VVT lock pin testing".

Dragonflyer

As I understand it: the timing chain drives the intake phaser and exhaust phaser is driven by the zero-backlash gear which meshes with intake gear. The cams are driven by phasers through a valve which uses oil pressure to modulate cam position with respect to that of phaser. What I am not sure of is the pinning of disks with timing circles: are they pinned to phaser gears, which are driven by timing chain or to camshafts, whose position is varied by a valve, which is actuated by solenoids. If I understood you correctly, those disks are pinned to camshafts, not gears.

During my observation, I did not notice those disks lurch forward, they pretty much moved according to me rotating the crank as if they were pinned to gear heads.

For a number of years, I've been noticing the car's tendency to jerk upon applying brakes as if brakes were grabbing, especially at low speed. I suspected transmission, so I serviced it last year and installed a new filter but it did not get better. I have new rotors and brakes and bled the brake system but this "grabbing" feel keeps getting worse. Sometimes, when almost at a stop, the engines surges as if transmission is slipping out of gear. Now that I better understand the concept of VVT I could theorize that a sudden change in camshaft position with relation to the gear it is driven by could result in such surge. When I was installing the new timing chain I took a good look at crankshaft gear, balance shaft gear and phaser gears. I had a new crankshaft gear to install but did not because, when I compared the two, there was hardly any difference in gearteeh shape. The balance gear also looked good. But the phaser gear teeth that mate with the chain did look sharp and pointy indicating wear. I did not replace them and I did not take them apart to look inside.

Have fun with that door lock module!

CaliBenzDriver

I do hear a snap in your video... it sounds like the camshaft rushing forward die to worned out lock pin... (VVT RIP??)

The VVT Phaser is driven by ECU through the "magnet" controling oil input qty based on input by CPS eyeing the camshaft.

When oul pressure is too low the lock pin extends to lock the Camshaft to input shaft - When that fails the camshaft gains 1/2 inch of travel freedom. The CPS reports a position that the ECU dislikes enough to set a code.

If you can confirm the lock pin is useless, go ahead and replace both Intake VVT Phasers. Exhaust are less involved at low RPM (save 'em!).

In the meantime for all of us, make sure you use good oil viscosity that last past 2500.Miles. VVT are powered by oil pressure that is closely related to viscosity... so I use serious Motul or PenzOil because oil specs are self-certified: they are compatible with whatever they label they buy.

Dragonflyer

<<Exhaust are less involved at low RPM (save 'em!)>> that was just the advice I was looking for

I use Liqui Moly Molygen 5W-40.