Oddly enough, I tried to buy that gauge yesterday. Went to 3 different automotive stores and not only could I not find it, the folks didn't know what I was talking about. Thanks for the link.

 

Whoa, wouldn't say I'm selfish and I try to help a lot of folks out. I don't come here often and have not received any emails requesting help (I changed a setting now to allow emails, didn't know about it)? My issue is not resolved, however the misfire only occurs at Wide Open Throttle or close at right at/near redline where the shift point would be. I've changed O2 sensors, checked for blocked cat, swapped coilpacks, etc. nothing has resolved my issue. I did have another issue this morning that maybe related. It wouldn't start and I wasn't getting fuel. Let it set a while after trying a few times and checking fuses (removing it and relay). It started. I'm wondering if the pump is failing, even though I replaced it a couple years ago. It was aftermarket URO or something, wondering if it doesn't create enough fuel pressure or if it is failing slowly? Or not related and maybe my second CPS, replaced the first one early on in its life, now over 218k miles, might be that again?

 

Well, as it turns out my catalytic converters were completely plugged. The front cat was empty and all the baffles were in the rear cat. Not sure this will help everyone but it's the fix for this ML55. If course I'll need to do the other side asap but this gets me on the road today. Paid $900 to have both cats installed.

 

https://www.dropbox.com/s/wt64deyhid...38.04.jpg?dl=0






That's the baffle from the front catalytic converter in the tip of the rear cat. Replaced them both and the problem has been resolved.

 

I supplied you with an ebay link and art rev supplied you with an Amazon link for the gauge.

 

Pretty sure its the CPS for the starting issue, only happens once warmed up. If it sets for over an hour or so it will start.

Still haven't figured out the misfire, but I'll not accelerate hard and its fine, but wish I could figure it out without spending an arm and leg at the dealership.

 

paulzale, when last did you change your fuel filter?

 

Trying to get supplies to friends after the hurricane. Ml320 runs great on the highway, but when I slow down in the little villages, the car starts to run rough. Usually a 5 minute rest gets it straight again and/or disconnecting the battery clears the codes. A mechanic in Ensenada diagnosed a bad battery. Replaced and problem went away for 300 miles. New mech had a look and discovered broken motor mount. We will be replacing those in a few days when the parts arrive from the us. My theory is the engine is torquing so much it is making electrical contact with something. Nobody around here has a code reader for MB. Anyone has an idea, my only contact with the outside world is Facebook user Bill Schmiett or this forum. Gracias

 

Broken motor mounts are very important to the proper running of the truck. Get them replaced and post back with any further problems.

Please UPDATE YOUR PROFILE in USER CP.

 

Well I did get the motor mounts installed, 3 days to get the parts. No help. I pulled the coil wire off #4 and there was no difference in the performance. Order a coil 3 days later it arrives, new plugs, no bueno. Now he tells me he has the scanner! Misfires on 4,5,6 Pulled the O2 sensor out and it sounded like a lot of Mexican cars, but it ran well. Cut the front converters out and replaced with a straight pipe. Runs great! I didn't realize they didn't cut out the back ones and off I go into the desert. 45 miles later the issue is back and 15 miles of limp mode into the next town where I located a guy who cut the back ones out. Looks like honeycomb as in the picture above! replaced the converter with a pipe and BINGO!

Runs great and my county in CA doesn't have to have a smog test because the air is clean enough. I'm driving this baby until it drops just as it is!

Thanks to everyone who posted!!!!!!! I'd probably still be stuck in MX without you.

 

hey guys i am a newbie here but experiencing the same symptoms. I removed my ds o2 sensor and cel has stayed off but still reading misfires on cyl4-5-6. i have a scan tool and reset it but it comes back. i just put new plugs in it. The gas in the car is about 2 yrs old so probably not helping. I filled up with about 10 gallons of 93 oct. short of doing a compression test i am running out of ideas. any help would be appreciated.

 

When one bank 4,5 & 6 misfire, it is almost always an indication that the catalytic converter is clogged or broken apart.

 

yeah that is why i pulled o2 sensor and the cel didnt come back on while i drove it up and down the street. i guess i was just wondering why it is still recording misfires on my scan tool after i removed it. I would assume that the cat is really clogged. I was under the assumption by removing the o2 that all misfires would go away but i may have just misunderstood. thank you

 

Removing the O2 is a diagnostic measure to figure out if the CAT is clogged. Removing the O2 sensor will also create confusion in the ECM concerning the particular bank were the sensor was....So you will still have misfires. The correct thing to do is fix your CAT.

 

Thank u that is what I was wondering. I am going to just was curious as to why it was still misfiring but thank u for clearing it up.

 

That's a very confident reply BUT my CATs on both sides were replaced a few months ago. I don't have the funds to spend on more mechanics bills atm. It'll have to wait. When I have time I'll have the CATs swapped and reconnect them to see which bank shows a misfire. This will either diagnose a faulty O2 sensor or eliminate them from the possible list of faults.

 

Plasticbaldy. have you changed all 4 CATS? If you have changed upstream ones , then most probably your downstream ones are clogged or vice versa......
Faulty O2 sensor will give you a code.

 

Mechanic removed 4 CATs & installed 1 new after market one each side instead. Vehicle ran fine till the misfire codes caused one bank to go into limp intermittently. Shutting the engine down & restarting would cure it for short times. The mechanic assures me that the O2 sensors send the misfire messages to the computer. Either they are faulty or there is another reason for actual misfiring. Yet to be determined.

 

O2 sensor doesn't send misfire messages. It analyses the oxygen percentage in the exhaust gases & sends the "data" to the ECM. According to the "data" ECM determines the correct fuel/oxygen ratio.

 

well i cut about 2 inches off both the primary cats at the bottom to see how bad they were. the ds cat is completely gone. so i am assuming its blocking the secondary cat on ds. passenger side cat is still intact. looks like i will be either ordering new cats or just welding in some pipes. thanks for the help guys. i drove around after doing this and no cel and no misfires..

 

Mechanic tells me that when the O2 senses raw fuel the ECM shows misfire codes and so a faulty O2 can result in misfire codes.
What's your opinion on what inputs to the ECM result in misfire codes ? My mechanic says there's only 2 inputs to the ECM.

 

misfires could be a result of a number of factors/(inputs). Cats, O2 sensors, plugs, injectors, plug wires, coils, MAF sensor....just to name a few. Localisation of misfires plays a big roll in diagnosing the problem. If misfires are only on bank1 or bank2 then there is a common problem that applies to all 3/4 cylinders in that bank. Most common scenario is a bad CAT which affects the whole bank. O2 sensor would affect the whole bank as well.
If the misfires are random the reason could be plugs, injectors, wires, coils etc.... So there are much more then 2 "inputs" causing misfires.
I think your BEST solution is have the car scanned with a pro level scanner. Get more actively involved in fixing of your car. Don't take what the mechanic says as gospel truth. After scanning the car you will get your answer in a code. You can post all the codes here & you will get help from our expert members.

 

I don't believe that I said that "2 "inputs" causing misfires."
And if I did then I was obviously wrong. What I said was that there are 2 inputs to the CPU that may 'tell' it of a misfire - actually only one of them, the O2 sensor, I think my mechanic said. There might not actually be a misfire but incorrect information being sent to the CPU may result in the vehicle being sent into limp mode. Maybe there actually is a misfire but if you care to read all the posts you'll discover that every electronic and fuel component has been replaced by various owners with this fault without success. As for blocked CATs, I repeat - All 4 of my cats were recently removed. One new aftermarket CAT was installed on each side to replace them.
As for 'getting more actively involved in fixing my car' please tell your brain surgeon to wake you during your next cranial surgery to see if he should cauterize your intercostal adiabatic haemorridal third transicular or just take that ****er out and feed it to the lab cat, buddy. lol Not many of us are qualified to **** with modern mechanical electronic technology just as you'd be a fool to 'get more actively involved' in your brain surgeon's handywork. WTF do you think we're wasting our valuable drinking time here for mate ? I'd be at the pub right now on the off chance they extended happy hour if I could stop my Merc limping. Or do you suggest I take my plumbers kerosene soldering iron with a 2 inch tip to the CPU and 'tidy up' any suspect solder joints so as to be "more actively involved" ? Hahahahaha Duuuuuuuuh ! (yep, I know. 'sodder' to you Yanky sods but the English word is 'solder' and you do claim to speak English I believe before you started having 'threepeats' or eating 'take out' right from the 'get go' while sitting on your 'fanny pack'. It may amuse you to know that in the English language 'fanny' is a polite way to say 'vagina'. lol)

 

Firstly, I am the one doing the surgery.

Secondly, if we all were qualified to **** with modern technology , we wouldn't need this forum, which is meant to help each other.

Thirdly, I am not a Yanky. Zimbabwe is in Africa.

Fourthly, I can see you are very good in English. Why don't you join a English literature forum, were you will be more helpful.

Ya, & good luck with your ML.
In the meantime I suggest not to waste time & catch a cab to the pub......

 

Nice. Hahaha. Yes. Guilty as charged. I didn't read your short profile details. At that time of night I incorrectly assumed . . . Sincere apologies for assuming that you're a bleeding Yank. Being literate doesn't preclude me from also understanding the goings on in mechanical & electronic componentry. (in fact I'm a mechanical Engineer) If I told you to **** off to a mathematics forum for your 'firstly, secondly, thirdly. . . etc numerical analysis it would be equally unfair Mr Zimbabe. However I doubt that even you are capable of understanding and diagnosing all of the electronic faults that now inhabit our engine bays even though you qualify yourself for brain surgery ? Eventually discovering the fix for limping MLs and the source of the possibly faulty ECM or ECM inputs that are causing misdiagnosis of what may possibly not be misfires at all that result in my trip to the pub taking an extra 15 minutes is why I'm here. It seems that so far nobody here has found a mechanic capable of finding the faulty culprit component. I'm not silly enough to waste money having all my ignition and fuel components replaced in the hope of discovering the fault by expensive elimination as your "Get more actively involved in fixing of your car" might be suggesting. Others have done enough of this and not found the fault or else they've pissed off and left us in the dark to argue.
If you read all the forum posts on this topic from the beginning you'll find answers to the alternatives you suggested in your posting of 11/3/2014. We've already eliminated your suggestions. Coming in late and missing the first half of the lesson has you asking questions already previously covered. But thank you for keeping the discussion going.

Please don't see my words as a personal attack and take offense. References to brain surgery, mathematics etc is all TOTALLY tongue in cheek. I need to amuse myself because I can't get to the pub in my faulty ML fast enough so I sit here looking for the solution.
I do need to apologise however for mistaking you as an American. What an insult ! Sorry.
Maybe Hitler is getting his revenge after all.