nobleeth

I bought my 2009 GL450 with 144K miles last month and this site has been a godsend so thank you in advance! Now onto the issue -

I changed all of my plugs a few weeks ago and the problem started. Could be coincidence, maybe not. The engine started running slightly rough at idol and I got a cylinder 2 misfire code so I swapped out the coil with a new one but the code came back. I then moved the new coil and the plug to cylinder 1 and reset the code and it came back again as cylinder 2 (telling me it wasn't the coil or plug), but then it showed a "catalyst efficiency below threshold bank 1" code as well. From reading the forums it's either the coil wires or the fuel injector. Or something bigger.

I looked at the wires closely and they seem intact - but they also do not look like something I can just replace one of as they are all zip tied together and running through some crazy wiring array. I could not even find the set for sale online but see a used full set on EBay (https://www.ebay.com/itm/MERCEDES-BE...-/262703832059) but I'd hate to replace the entire thing, especially with an old one, and that is not the problem.

As for it being a fuel injector, I looked on YouTube and it looked like a HUGE job but then someone here on the forums said it's an easy swap. I will do all of the work myself. Should this be my next step? They are only $40 on Amazon.

The strange thing is that the car runs perfectly when moving, and I only feel it when it is idling at low RPMs. It feels a little rough, but not crazy rough.

I would love some advice on what to do next! Thank you in advance!

UPDATE: TODAY, WHILE MY WIFE WAS DRIVING HOME THE CEL STARTED FLASHING AND THERE IS A PROBLEM ACCELERATING AND IT'S RUNNING ROUGH. Waiting for her to get home to check the code. I inspected the wires throughly yesterday, which means I moved them around. Maybe they are faulty and I made them worse??

Please help!!

nobleeth

Bump, and another update. I went to meet my stranded wife and ran the codes. The light was not flashing when I got there (it was just on steady) and now in addition to the Cylinder 2 misfire code and catalyst below threshold code it has a P0352 Ignition Coil B Primary/Secondary Circuit Malfunction code. This leads me to think it is not the fuel injector but rather the wiring. What scares me a little though is that when I was inspecting the wires a couple of days ago and I removed the ECM I noticed that two of the pins on the left hand side were a little rusty. Not very rusty, but just a little. I cleaned them carefully and reinstalled everything but perhaps this is a sign of moisture getting to the ECM?? I ordered a used wiring harness from EBay and it will arrive next week and it seems like a pretty easy job to install. An ECM is close to $1,500 though and I can't afford that.

If anyone has any thoughts on a possibly faulty ECM (would only 1 cylinder misfire??) or if there is something else I should be looking at let me know. I'm desperate and had to rent a car again for the week.

eric_in_sd

Did you clear the error code after replacing the coil? I seem to have found that the ECU has to be reset in order to stop it from slipping back into limp mode.

nobleeth

I did. A couple of times after I tried different things like removing the coil, swapping the coil with another one and retightening the plugs. The first time just the CYLINDER 2 MISFIRE came up. Then, I reset them again and I got the MISFIRE plus the Catalast Below Threshold code. Now, with the flashing CEL I get those two codes plus Ignition Coil B Primary/Secondary Circuit Malfunction code.

nobleeth

Okay - some more updates. The wires leading to the coil for cylinder 1 were run across the top of the pack for coil 2 so I moved them under the pack and reset the code. I am thinking perhaps the wiring going across the top of the pack was creating some kind of signal interference. I was probably the one that ran them across after the spark plug change I did when I first got the car last month, which was right when the problem started.

So... I drove it for about 40 minutes so far and the CEL came on again. This time with a totally new code, never before seen - P0013 Camshaft Position Actuator B - Bank 1 Circuit Malfunction. None of the other codes have appeared again. Here the thing though - I bought the used wiring harness and started to unplug things to be able to swap it out but changed my mind after I realized just how many plugs there were so I put everything else back together. I looked and all four plugs for the cam sensors are plugged in but perhaps I messed the wiring or connections up somehow when I started to unplug things??

eric_in_sd

Since you're digging this deep, quit using the term CEL. If your wife looks at another dude, the CEL will come on. Only think in terms of the OBD codes and the underlying data.

It could easily be RF interference from having the wires too close to the top of the coil.

It seems likely that you didn't plug the cam sensor back in correctly or something like that. Go back through, recheck them, maybe even clean them.

Take pictures before you start next time, so you can be sure you're reassembling it correctly. I only know this is a good idea because of all the times I wished I'd done it.

nobleeth

Thank you Eric! Do you happen to know what side Camshaft Position Actuator B Bank 1 is on? Is that one of the sensors on the driver's or passengers sides? I double checked the connections this morning but I will buy something to clean them with too. Can I just use electronic contact cleaner spray?

eric_in_sd

Bank 1 is the side with cylinder #1. In a U.S. car, that is passenger side.B is the exhaust, or outboard, side.
Don't know for sure, but: This is an engine compartment. You can spray damn near anything you want around there.
Looking at the description of that code in more detail, it seems obvious that you either did not plug something in correctly or there coincidentally was a failure. The former is much more likely, but do not rule out the latter.

nobleeth

I wound up bringing the car to a local European service shop (it has really high reviews on Yelp) and they are saying it's the intake manifold that is causing the problems and quoted me $1500 for the repair. While it's open, they are also replacing one fuel injector that I purchased separately, although the mechanic says he doesn't think the injector has anything to do with it. I am a little hesitant as I do not see how an intake manifold could cause a P0352 Ignition Coil B Primary/Secondary Circuit Malfunction code.

Anyone have any thoughts on this? I don't see how this could be the case especially when it's that same cylinder throwing the misfire each time.

eric_in_sd

That's tough. The intake manifold tumble flap is a known issue with a variety of levels of repair.

Don't panic and think you have to solve every problem at once. If you have a known issue, repair it. Find out what the nature of the intake manifold failure is. Sometimes it is repairable from the outside and sometimes it necessitates replacement.

I'd say it's most likely that they discovered the one issue and are basically saying, fix this first, rather than, here's your source problem. If you have a known problem, take care of it.

dbnh

Not to totally alarm you. I have had an engine 2012 ML550, 85K miles purchased 8 weeks ago. The engine has a slight vibration felt in the vehicle when idling. Can vary in intensity. The Code indicates a misfire in cylinder 3. I had an independent garage evaluate the problem and the car is showing low compression in cylinders 3 and 4. Took it to Mercedes toady after running for 500 miles prior to the CEL appearing again. Mercedes indicated (with diagnostics) confirmed the issue and wants to remove the passenger head for further evaluation. The cars performance other than idle is perfect. This is going to be a very expensive repair. I am open to thoughts on the matter

Thanks

donb

dbnh

I wanted to add to the previous post. The manual cylinder compression test varied from a low of 80 to a high of 150. All the readings are somewhat low since the bottom threshold of 175 was what I was told. Head one (150, 125, 90, 80) Head two (130,150,120,100)

Thanks again

nobleeth

I wound up paying $2,000 for a full intake manifold replacement along with injector gaskets, cam gaskets and an oil separator. I THINK it is idling better but my wife drove it today and says she thinks she still feels it. Fingers crossed that solved it and it isn't anything more major because I'm running out of money.

dbnh

Good luck.

nobleeth

Let me know what you wind up paying for the work. After doing some research it looks like you can get an overhauled engine for the x164 for around $3K plus install labor. Part of me almost wishes I did that because for another few thousand I could have had a new (overhauled) engine right now and not have to worry about it. That additional money would have been impossible to come up with though so I did not have the option.

dbnh

Just had a garage perform a leak down test on bank one. Cylinders 3 and 4 failed. The diagnosis is the exhaust valves or valve seat is causing the compression issue. No estimate yet but the labor charge will be around $1500.00 , then gaskets and the cost from a machine shop to perform a valve job on that head. The question also arises as to having the second head pulled and checked. The labor cost to tear down the motor may justify the additional head. Awaiting quotes to make a decision. Hard to believe a slight engine vibration at idle can lead to a big expense. Let me know how you are doing.

nobleeth

The intake manifold replacement seemed to fix my issue... at least, I think. I have not gotten the cylinder misfire since the job was done ALTHOUGH I still feel a slight vibration at idol and my CEL came on (and then went off) for a catalyst below threshold bank 1. I am going to swap the CO sensor and see if it stays off. I'm praying it's not the same issue that you have that is causing the slight vibration but since the CEL hasn't come on for the cylinder misfire it is hopefully not the case.

eric_in_sd

BUMMER

I recall from when struggling with my misfire issues that some motors had exhaust valve leak issues. I had the cylinder heads rebuilt under warranty - I suspect they knew about the exhaust valve issue, but told me it was carbon buildup because I put in bad gas - so I might have dodged a bullet there.

Problem is, with leaky exhaust valves, they never get better and in fact only get worse because the gap indicates an area where hot gases are leaking and it never seats to cool. Sort of like the Shuttle booster seals.

TBH I'd for sure do both heads while in there. Unlikely that the other valves aren't also marginal. However, I'd also make sure the rest of the truck is worth investing in. How's the tranny? The rest of the motor? The body, interior, etc?

eric_in_sd

Tip: Forget about the CEL. Your cat errors, for example, don't mean much and could be due to a wasted cat, a weak oxy sensor, or marginal upstream oxy sensors, or MAF sensor issues ... it's a downstream indicator. Of course, the sensors aren't hard to change, and they do go bad; if I were going to the trouble of swapping it, I'd just replace it with new, if it had been in there for 100k+ miles.

dbnh

The vehicle is great condition in and out. That is the reason I am considering the repair. Thanks for your input.

dbnh

The final outcome of the misfire and low compression in Cylinders 3 an4 has been resolved with the rebuild of the passenger side head. Bad valve guides for exhaust valves. Replaced all exhaust valves in the head. Final cost $3300.00. ( ASA certified shop) I never expected to encounter this scenario with any car especially a Mercedes top line SUV.