Roop94

Hello everyone,
I have had engine misfire for a bit now. Diagnosing little by little, but I have found nothing yet. First I thought it is misfiring from one bank, but the shop guy said it's from both sides.

So I checked the coils, they are good. Replaced plugs (one turned out to be broken or lose, whatever the term may be). The misfire is still there, though it has gotten a little less. However, I drove it today and wanted to see what changed...it drives a bit smoother than before in low rpm, feel a little shake/jerks, but when I floored it, past 4krpm, it's misfiring whole lot. The speed barely went up. It's misfiring at high rpm even more now. Last time I ripped it at high rpm for about a minute, the pull was fine. No shaking or jerking. Today, it didn't shake, it just misfired a lot and didn't speed up.

Had a CEL 2 weeks ago and changed an injector. No other lights on or anything...Idk what to do. I even uninstalled the EuroCharged tune I had and put it back to stock numbers untill I can get it fixed.

The mechanic told me to just drive it on a long drive and lets see if CEL comes on, I don't feel comfortable doing that. He said the same thing when he replaced the injector before and I changed the broken plugs, he still saying the same thing to keep driving.

Any other ideas/suggestions on where I should look? It could be the MAF sensor, but there is no CEL on. Someone pls help.

CLSPilot

I dunno, sounds like fuel starvation. If its misfiring a lot when you throttle it, it can mean(sometimes) that the fuel flow isn't keeping up with engine demand. Have you checked the fuel pressure? Not sure about this car, but I can tell you about my S6(5.2L V10). It had a regular fuel pump, then on each bank it had additional high pressure fuel pumps. Direct injection cars need the high pressure fuel to overcome the pressures in the cylinders. Since you are misfiring when rpms are higher, I'd gander to say you had a high pressure fuel pump problem. Driving around a lot would not be beneficial as you'd be running lean, which isn't good. Just a suggestion, but that's where I would start, high pressure fuel pumps, maybe the regular one too. Check fuel pressure from the tank and also check pressure coming from the high pressure pumps.

Roop94

Yea that was one of the things that crossed my mind, but it turned out I had a few bad coil wires to the plug. I replaced 2 coil boots on the one that had a broken plug and a bad injector...the misfire is gone. But I need a replacement of O2 sensor, which is about 25 to 30 bucks. Just replaced two coil boots this morning and cleared the codes. misfire is gone and the power is back. Going to drive a little for the CEL to come back and re check it. Next time I go to the shop I am going to ask to check the fuel pressure.

I think it all started with a bad spark plug lol that little piece of **** lol now the O2 is gone.

bob2011

Bump, let's get this figured out bro :/

Roop94

no info input here...moving to w212 lol

TrapMoneySonny

See if you got a cam sensor leak. I took my car in cause the CEL was flashing, they said it was bad injector, o2 sensor code came up as well, they found oil in the injector and oil on the o2 sensor, said its leaking from the cam sensor. The oil is leaking from the sensor on to my harness and said I have to replace the engine harness and all the sensors its attached to.

rick hesek

Have you measured the cylinder compression? All cylinders?

Colin Carby

Hi Rick!

I hope all is well.

I saw one of your posts and had to reach out.

We have a 2012 cls 550 with 53k miles, and have had rough idling in the mornings when starting, then it eventually warms up and goes away.
The dealer found oil in/on the harness /02 sensors that seems to be coming from the cam sensor.
Does this cause this problem? The car is occasionally hesitant when gassing it, but still have amazing power when accelerating.
I really could use some help, for I am not mechanically inclined. LOL

Thank you in advance.

rick hesek

Hi Colin,
I don't believe the oil leak, onto the harness plug, would cause that rough idle. Mainly because the idle smooths out when warmed up.
Oil will become less viscous (more fluid) when warm and prevent the idle from smoothing out. In other words, if oil was causing a rough idle when cold, it will cause it when warm, as well.
There are many things that could cause the rough idle when cold. Seeing that you have only 53k miles on your car eliminates many.
Have you had the spark plugs and/or ignition coils replaced?
The O2 sensor harness plug is far away from the cam position sensors. However, one O2 sensor is right below the oil separator (crankcase breather). These will leak oil both outside and in to the engine intake. Another symptom of the leaking oil separator is blue exhaust smoke upon startup.
I assume your check engine light (CEL) is not on? There may be a pending issue that have not triggered the CEL to come on. Especially, since your problem is intermittent.
The early twin turbo V8's had a timing issue that I don't completely understand. The first symptom is an engine rattling noise upon startup. I own a 2009 non-turbo CLS and I am looking for a newer one. That is why I am on this forum.

A good place to start is to go to an auto parts store and ask them to check for codes. Should be a free service. If there are any codes, pending or otherwise, write them down and report back here.

Colin Carby

Hi Rick!

Many thanks for replying.

Understood on the rough idle, but what will this oil issue cause? The dealer said it causes it, but they seem to be guessing, even though there are visible signs of the issue.

I have not changed the ignition coils, but I believe we changed the spark plugs in the past. (Girlfriend's car)

As I am not mechanically inclined, I am curious, can the 02 sensors be cleaned off or once they get oil on them, they must be replaced?

Only the check engine light is on, not CEL at this point.

Their does seem to be a light rattle when cold starting only, but is fine once the car gets into"operational mode."

It is at the dealer waiting for the warranty adjuster to review it. (O2 sensors are not covered, hence the question regarding cleaning it... May be absurd, but learning.)

The diagnostic fault code mentioned "Rich Gas mixture," along with the actual values for all the cylinders operating within their required specifications.

Tks again for the education.

rick hesek

Hi,
I am learning about the M278 engine also and may be limited as to what I can offer.
Spark plug replacement is due at 80k miles. Just a thought in case you replaced them to eliminate the rough idle.
The element part of the 02 sensors screws into the exhaust pipe on each side (V8, dual exhaust), so, it is not likely oil is getting on the sensor element. If oil is getting into the electrical plug, portion of the 02 sensor, then yes, could cause a problem. But, as I said earlier, this theory does not hold up since your idle smooths out.
The Check Engine Light is the CEL, one and the same.
I would post a separate topic specifically for the issue you are having. MBWorld is a great resource and users will see your subject line and reply.
This post subject is "Engine Misfire. A lot of shaking/jerking". Your subject could be: "Rough Idle at start, smooths out after warmup". Something like that.
I am curious to hear what others have to say/add. It would be helpful to know what codes are causing the check engine light to come on.
The link you added is a link to your Outlook mail. No dealer diagnosis info there.

Rick

Colin Carby

Hi Rick!
Good point
My extended warranty has agreed to cover the harness, computer, and all sensors.
Once they fix it, I will try to post under the actual topic.
I am curious if any other components connected to the harness will be adversely affected.
Tks

rick hesek

Well that is good news. Ext warranty's are good not because these cars are riddled with issues but because the repair cost can be devastating.
I feel the only way other components can be affected by a harness swap, is that the new harness being damaged before the replacement.

Rick H

Colin Carby

Hi Rick!
I was thinking the old harness that is being changed this week could have damaged other components than what they are changing out.
They are changing all 02 sensors, cam sensors,harness, and a computer that are linked to the harness.
I was thinking other components could be damaged as well, or deteriorating and will become an issue. Thoughts?

Romann001

I would sugest your MB dealer to do compression test for you(only by diagnostics-no need to take a plugs out)...so you are sure you dont have something like this: ..move to 29:00..bad cylinders ....bad pistons..

Drewsky00

While the symptoms are not exactly like OP's, I am having the same thing happen to my '16 550 with a Eurocharged tune with burble option. Sputtering engine, lots of jerking, like the engine misfires, etc. -- but unlike OP, this can happen while I'm sitting idle in morning commute traffic. Runs rough for 1-5 minutes, then it goes back to normal. Took a while for it to happen again after the very first time it happened about a month ago, then it became more often, not it seems to happen every time I drive it. CEL came on a week ago, I stretched the engine a bit, it backfired like it was unclogging something, then went back to normal. Stopped for gas and turned off the engine, when I turned back on, CEL was gone. As of yesterday, CEL came on and stayed on. I removed the tune in case it might be causing or contributing to the issue. Funny thing is... it still backfires lightly at times now, even with the burble tune removed, hmmm. Waiting for a friend to pull codes tomorrow to see what to do next.

Drewsky00

Update: Got a friend to read code and it says "P0355 - Ignition Coil E Primary/Secondary Circuit". Gonna schedule an appointment with the stealership since the car is still under warranty. Thoughts?

Romann001

The first thing I would do is a compression test...just to be sure, that your cylinders and pistons are good....if you have bad plugs and coils-it cost to repare nothing to compare with bad cilinders..

Roop94

I've been away for a while.

I also had the EC tune with burble. What I did was that I swapped all my coils from Bank 1 to Bank 2 of the engine...and just by doing that, my car started to run smooth. No shaking/jerking anymore, at all. I think maybe some wiring might've been loose on some coils? No clue at all.
Another thing was that later, it started showing misfire on all cylinders on Bank 1. The mechanic, knowing nothing about these cars and how ECU/OB2 tune works, told me my tune ****ed up my software and I must replace the software, another $1200. What I did was changed the Upstream O2 sensor on Bank 1. Car is back alive. Been a month.

Now, I'd suggest, if you have burble tune with cats on...remove the burble tune. I highly believe that's what shot my O2 sensor and caused all this headache. I'm planning to reflash and remove burble tune from Stage 1 tune and later get Stage 2 w/ burble. then there are no cats and O2 sensors that can be destroyed lol.

At least, that's my story and solution haha.