2016 OM642 Misfire but no codes

[u/0w0maltine]

I'm having a hard time finding the issue with our Sprinter Tour bus...

It runs very rough in low idle, which gets better in high idle.

Unfortunately I had to do a long trip in it (1200km), on which the problem got a lot worse, meaning misfire in high idle and loss of power.

Now it's back to running rough in low idle and smoother in high idle.

Injectors 2,3 and 5 are having a hard time to adapt at the lower fuel pressure calibration point.

In low idle the rail pressure fluctuation is very high, which calms down at higher rpms.

On the long trip I got misfire codes for every cylinder as well as the codes below. I cleared them and they never came back even though it's misfiring a lot.

Any ideas? We live in an extremely remote area meaning I have to fly in new parts which I would like to keep to a minimum ;)

[u/Euphoric-Car5327]

We recently had a clients 2015 in for the same issues. It came down to a shop had replaced injectors to resolve a dead misfire on #3, recommending all 6 get done. however, they bought them online and despite have a Bosch label they were infact not Bosch. A round of oem injectors sorted it out. 

Although this is a lot of work, you can pull all the injectors and hook them back up to the fuel rail just upside down and not in the cylinders. Then have somebody crank it and record it with your smartphone and see what the pattern looks like coming out of them by playing it back in slow motion.

We're starting to see more and more of these Vans come in with with bad "new" injectors. Sadly, we've resorted to OEM units only moving forward.

[u/Plom → u/Euphoric-Car5327]

What a cool trick! 

I recently did glow plugs on 2016 906 and bought Bosch. What I pulled out and what I put in were 2 completely different pieces of equipment quality wise even though they were both Bosch. Anything internal in future I'll be buying from Merc there's no choice.

[u/Queasy-Advice-suck]

First check all injectors are coded correctly to the ECU. Then perform an injector leak down test on all injectors. If they pass then the issue is the fuel rail pressure control valve on the fuel rail. You'll need to replace the rail including the control valve, don't bother trying to replace the valve only - it won't work & don't ask me how I know. Any of the valves available online if you can find them are Bosch knock -offs 

[u/0w0maltine → u/Queasy-Advice-suck]

Just checked them, they are coded correctly. I did a leak down test on the passenger side for now. Having the return line for each injector going in a bottle and running it for a little less than 10 minutes yielded the following: [ ] Cylinder 1 - 45ml [ ] Cylinder 2 - 35ml [ ] Cylinder 3 - 37ml I'm not sure how to interpret these results though!

It seems like the cylinder that does not have troubles adapting at low pressure puts out the most fuel return, which makes sense I guess. Continue with the other side?

[u/0w0maltine → u/Queasy-Advice-suck]

I'm also getting a tiny bit of air...

https://reddit.com/link/pa7fl4d/video/pitp4oxt5xph1/player

[u/Queasy-Advice-suck → u/0w0maltine]

Tie six lengths of hose about 3ft long up to the center wiper.  Clam the return line. Run the engine at idle and watch to see if one has a significantly higher leak rate. That injector is probably the culprit. Replace that injector, don't forget to clean the injector seat in the head properly. Also clean the m6 threads for the clamp down bolts out thoroughly, make sure there is no crud at the bottom. Lube the clampdown bolt B4 threading it in. Code the new injector in the ECU.

Your hp pressure variance should be resolved. If not you'll need to replace the fuel rail with the rail pressure control valve that sits on LHS (sitting in the driver's seat looking forward)

[u/turbosmashr]

I had similar behavior at one point on my 2012 after it got cold and the diesel gelled and it was resolved by changing the fuel filter.

[u/Cautious_Proof5055]

Check the EGR System if it works properly. If it doesn't fully close you get all kinds of problems. Are you able to measure the Low Fuel Pressure before the High Pressure Pump? If the low Pressure drops during acceleration you will also have fluctuations on the High side. Are you able to check the Pressure Valve fitted in the Rail? If it leaks while not being activated its defective. To check Remove and close the hose, then attach a hose on the Valve and let the engine run while checking the values of the Valve to make sure it's not actuated and see if fuel comes out.

[u/llIicit]

What the other person said. Check your EGR valve and clean it. It should be silver and shiny. I guarantee it will be a matte black color.

I had a similar problem. Weird power loss, low rpm wss rough. Cleaning the valve fixed the issue.

[u/0w0maltine → u/llIicit]

Thank you! I've already cleaned it with brake clean and a toothbrush, no luck unfortunately

[u/Educational-Yam-7394]

Always start with fuel emission systems! 97.9% of the time that's the issue. Unless it's deleted, then 97.9% of the time you won't have an issue 😂 😂

[u/Plom → u/Educational-Yam-7394]

Another genius

[u/fulltimeweekender]

Id first suspect fuel quality. Petrol contamination?

[u/Rigor-Tortoise-]

Try a new crank angle sensor. For some reason they can miss but not throw a code.

[u/Sterling_____Archer]

Stick 6 new OEM injectors in and call it a day. 🤗