embassured

This may be old news for some but I've had a difficult time finding anything on the internet. If you're in the same boat, here's what I've experienced...

2012 CLS550, 29,300 miles: Check engine light, huge misfire, very difficult acceleration with severe vibration. Feels like the catalytic converter could be plugged or a cylinder (or cylinders) not firing. Take it to the Merc dealer - they replace an injector and I pick up the car. Three days later, the exact same problem occurs again. That was 2 weeks ago, which equals the amount of time the car has been in the shop.

In that period and as I've been told, the problem was traced to a leaky injector, which also leaked on (and corroded) the engine wiring harness. Currently, all the injectors are being replaced with an UPDATED version. Additionally, the wiring harness (or at least part of it), some number of coil packs and an O2 sensor (fouled by the excess fuel) have also been replaced.

Here's the kicker - supposedly, the dealer has seen this problem (last year) on one other gas direct injection engine and since my car came into the shop another has also come in with the exact same issue. According to the advisor, Merc just released an internal bulletin (LI) last week addressing the issue and the need for updated injectors. They would not provide me with the LI# or details of the bulletin. I got the awkward feeling this is something bigger than just a simple issue affecting a few cars.

They've struggled with this repair and I'll repost once I have details of the work performed.

If anyone has additional insights, they would be greatly appreciated.

Best,
Eric

embassured

The dealer is unable to fix the car, has stated "no mas", and filed a "TAC" request; basically stating they don't know what else to do and we need someone from the factory/engineering to intervene. I'm waiting to hear from MBUSA to understand their suggested course of action. At this point, my faith in the car is less than solid.

Again, any insights about the problem itself or how to best discuss this issue with MBUSA would be welcomed.

Thanks,
Eric

embassured

Just to complete this post for future reference; the car is back and so far, it appears to be back in proper running condition.

The culprit for all the work seems to be the faulty/leaky original injectors, which have all been replaced with an updated version (see original post). Total tab for the warranty covered work was $4,500 - so not a small job.

If anyone has this issue going forward; feel free to contact me via PM.

Eric

OldMerc94

Old thread, but I picked up a CPO ML550 and had the CEL come on less than 200mi after leaving the dealership. The CEL was triggered by the Fuel Pressure Sensor which apparently was stuck in an open circuit. I had no ther real symptoms in the drivetrain - just the light.

After replacing the sensor (took a week to get the part in), it immediately faulted out again.

Problem was traced to the ECU and wiring harness which had an unknown fluid (based on SA feedback) seeping through the wiring and into the ECU itself.

The dealer replaced the wiring harness, fuel sensor, ECU and all the injectors. Vehicle has been at the dealer for almost 2 weeks now - total time absorbed by tracing this out has been about 3 weeks.

I should pick up the vehicle today. All is covered under warranty, but the cost estimate is pretty close to the OP's CLS repair. Thought I'd add this in as something to watch for if you're considering a Merc with the M278 motor. I agree with the the OP - this doesn't look like an isolated issue.

I'm adding this here since I just googled 'M278 Injectors' and this thread came up first. My W166 was an early build (Mar/Apr 2012) - so the older injectors may have this common issue.

embassured

OM94 - saw your message and glad your ML is on the road to recovery.

Your post fired a thought...my CLS is an early build M278 as well; i.e. December, 2011. So maybe it's a function of a bad batch/engineering of the early injectors.

Good to hear you've sorted through the problem and thanks for posting your experience, hopefully it helps others that are similarly affected.

Best,
Eric

TopGun32

looks like I had the same issue with Cylinder #3 injector. Misfires at anything past 5k rpms.

Dealer replaced coil pack and plug and did not fix.

I replaced all the spark plugs (1 step colder).. did not fix.

Dealer replaced injector and fuel rail on Cyl #3 and flashed my ECU back to stock. I have not ran it hard but the engine is very smooth and responsive now.

I will be testing the engine a few more days and plan to re-flash the car with a stage 1 tune.

I love my dealer.. no issue on working on tuned car.

zulumerc

bump..so what was the cause of your issue topgun? Did you get the tune put back on?

Redbeard

Dealer replaced right bank injectors and replaced oxygen sensor. This is the second fix for the problem. Confidence is very low on the car taking a long trip with only half of the ejectors being replaced. Was told to run until failure for the other bank. I didn't know that Mercedes was a run to fail company. With this type of problem why would you put your customer at risk of possible fire damage upon injector failure. I was told they will not replace injectors until failure. Any help would be appreciated.
Rich

LandSeaAir

2012 M278

Misfires at high RPMs and afterwards the CEL comes on and there is a very rough idle. If you restart the car, it goes back to normal.

Checked the codes... getting a misfire in cylinder 4 and cylinder 6.

Is replacing the injectors feasible for a DIY mechanic?

Do you have to replace the entire fuel rail, or can you replace each injector?

ItalianJoe1

High rpms is not usually an injector. I've seen a bad high pressure pump (unlikely in your case as it's both sides, and there are two separate pumps), but further diagnostics would narrow it down. I'd start with plugs and swap coils around, ensure it doesn't follow. Use OEM plugs and torque properly, it matters.

Injectors are easy enough to replace, but you have to code in the variant # on them, which requires an SDS computer. It can be done after the replacement but you would still need to pay an MB indy shop or dealership tech to do it for you, unless you have an SDS.

Don't have to replace the entire rail, each injector comes off. They have a special seal package that should be replaced, it's a bit more involved than a simple port injection setup. The teflon seals on the injector tips require special tools but a new injector comes with the seals installed so you don't have to replace them, however if you remove the rail and the other injectors come out you will have to reseal them.

LandSeaAir

Thanks Joe, going to try this.

funkypost

Bump Any updates as here we are in 2020 and it still happening as evidenced by my wife's 2012 E550 Cabriolet. 3 of the 8 injectors were dumping oil along with fuel. My service advisor said to sell it (I think he was upset that I told him to pound sand with his 5600 dollar quote). Currently have an indie working with me to swap out all of the injectors, O2 sensors and plugs. Thanks