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First time poster (dont yell at me) 2nd mercades i've owned. 31K miles, I've had it for 5 months. Purchased with 25K miles. one day car started missing, flashing CEL and then a solid CEL. nothing on command screen. had it scanned misfire Cylinder 5. took to a local shop and they said it need the coil boots and new spark plugs. they noticed there was water in some of the spark plug holes and oil in one (the oil they said was caused by a broken gas cap which I replaced. I picked up the car as i was driving home. As i was heading home (about 20 Min drive) it started doing the exact same thing, misfiring, flashing CEL then solid, then it had a defernite misfire (shaking, sluggish acceleration, etc) I got home as i was right up the street. waited a few hours. started it again. NO CEL, i let it run to heat up... i went back out to check it out about 15 min later. sure enough it was on and missing. I've only had the car for 5 months. should i get out? I baught it with a renntek tune. I wasn't going to but everyone on here and the folks i know say its a good tune and are very reputable. i'm taking the car back to the shop tomorrow to drop it off and tell them its not fixed. any ideas?? thoughts? get rid of it? came from an 18 750 which i loved. everyone said the benz had a more reliable engine that the BMW. any input or advice would be appreciated
Your Cyl5 misfiring is a staple of that Bosch ECU... by now we can only hope there's a firmware update that prevents that.
Realize Cyl.5 is bank-2 first cylinder, its also the particular cyl. that chews its rod bearing with bad timings.
I don't think any injector work is gonna fix this durably....
Something is causing the ECU to mess up its timings and catch-up on B2's #1.
I trust this is actually a combination of stock conditions ("snowball") compounding to cause Cyl.5 misfire as the ultimate result of poor combustion timings.
Random misfires would be remote relatives.
At any rate, misfires are the absolute opposite of powerful drive.
Last edited by CaliBenzDriver; Feb 23, 2025 at 08:44 AM.
Thank you for your reply. Do you have any advice if i should have it fixed or looked at again? with that low miles i was surprised that something happened like this. I had no Idea about the Bosh ECU thing. is that something an Indy shop can fix? or would i need to take it Merc. dealer? lastly should i just get out? I told the shop i'm not going to get in the just throw parts at it business which is what happened it looks like. Very good shop though maybe they thought it was resolved. Hopefully I can get it figured out. thanks again for the reply. I love the car, don't want to get out but I maybe should
EDIT: As i was driving it to the shop today to drop it off, the CEL was on but there didn't feel like any miss. I got about half way there the CEL started to flash, then back to solid CEL. At that point i could feel the sluggish acceleration and the miss. very weird
Thank you for your reply. Do you have any advice if i should have it fixed or looked at again? with that low miles i was surprised that something happened like this. I had no Idea about the Bosh ECU thing. is that something an Indy shop can fix? or would i need to take it Merc. dealer? lastly should i just get out? I told the shop i'm not going to get in the just throw parts at it business which is what happened it looks like. Very good shop though maybe they thought it was resolved. Hopefully I can get it figured out. thanks again for the reply. I love the car, don't want to get out but I maybe should
EDIT: As i was driving it to the shop today to drop it off, the CEL was on but there didn't feel like any miss. I got about half way there the CEL started to flash, then back to solid CEL.
At that point i could feel the sluggish acceleration and the miss. very weird
> From your driving experience you can tell it is a logic condition that upsets the ECU operation.
I would not be surprised when this naturally progress to include Cyl.#6.
> How to turn this disfunction back to neutral stock?
Take 5mn to use an MB scanner and clear the ECU faults.
This will cause ECU to relearn mixtures.
Then note how long it takes ECU to rebuild lean maps little by little.
This validates it is a software issue, not defective injector.
Taking this to the local MB dealer is a pretty good idea to flash the very latest stock ECU update.
Last edited by CaliBenzDriver; Feb 23, 2025 at 11:05 PM.
Also you don't have a good shop, they didn't diagnose your issue, they removed the boots destroying ALL of them (or at least charging you for them) and then just sent you out the door without a care.
The shop wasn’t able to recreate the issue supposedly. They took it out driving it. I explained that in addition to it missing while driving it was also missing while just idling in the garage. They were going to let it idle for 20 min or so. Supposedly nothing. They saw the code, after clearing it didn’t come back. They swapped oils from one side to another. They are going to let it idle tomorrow and drive and few miles and then go from there. I’m at a loss. I called Mercedes and they said they couldn’t tell me if it needed an update or not, it would cost 250 for them to tell me if it did or not
The shop wasn’t able to recreate the issue supposedly. They took it out driving it. I explained that in addition to it missing while driving it was also missing while just idling in the garage. They were going to let it idle for 20 min or so. Supposedly nothing. They saw the code, after clearing it didn’t come back. They swapped oils from one side to another. They are going to let it idle tomorrow and drive and few miles and then go from there. I’m at a loss.
I called Mercedes and they said they couldn’t tell me if it needed an update or not, it would cost 250 for them to tell me if it did or not
What you summarize is the standard experience... it's not easy to get anything fixed!
As if your problem was singular and unseen ever.
The reality is the opposite: these engines/chassis are designed to easily disfunction.
Its up to you to decide how to tackle your car maintenance. Personally I like to combine items.
Select a few dealer service items to get your car worked on and ECU firmware update researched so in the end a few items will have effectively improved.
Such as engine oil, tranny oil, ignition tune-up, with CPS "oil-in-harness" checked.
In addition research with your custom ECU firmware provider how your mixture issue relates to other customers.
Or you can do real diagnosis and address actual problems for a fraction of the shotgun approach.
But you'd need to learn or find a good shop, preferably both.
Was the coil pack changed?
As stated fuel injector would be suspect.
Diagnostic should be:
Change coil if only boot was changed
If problem persists check compression and fuel trim info to determine next steps
A tune always increases the damage profile, with low mileage that should be less problematic but anything can happen.
I agree.
This is exactly the same issue I have had twice. The coil malfunctions like this intermittently, until it fails completely. My dealer couldn’t find it. My Indy did once I had scanned it for codes.
You need the coil for cylinder 5 replaced. Also replaces cylinder 6 as well (2 cylinders per coil). They just did boots, which will not correct the problem.
Speaking of cylinder numbering, what is the scheme for Mercedes engines? Is it true that the front cylinders are 1 and 5 on passenger and driver's side respectively? Is this true of all recent V8 engines or just M176?
Speaking of cylinder numbering, what is the scheme for Mercedes engines?
Is it true that the front cylinders are 1 and 5 on passenger and driver's side respectively?
Is this true of all recent V8 engines or just M176?
Yes, cylinder count starts at LHD passenger side: 1-4, so the high numbers are on driver side: 5-8.
Actually that's what they are doing All Coils/Boots/Spark plugs. Hopefully that will resolve the issue. I wish they would of just gone with what i suggested but i get it they have to do their own diagnostic. Under gap the new plugs by how much? is that for the Renntek tuen? do you have anything i can read on for that?
Actually that's what they are doing All Coils/Boots/Spark plugs. Hopefully that will resolve the issue. I wish they would of just gone with what i suggested but i get it they have to do their own diagnostic. Under gap the new plugs by how much? is that for the Renntek tuen? do you have anything i can read on for that?
Slightly under gapping help ensure a reliably timed spark and preserve prematurely breach coils windings.
Meaning the wide stock gap is not what's best.
There's no denying you have to have great timely sparks but these premature #5 misfires are courtesy of the ECU logic.
Shops make misfires go away for a while with coil+injectors then they come back as ECU relearns exact same timings based on new parts.
Deal with getting a great reliable ignition now. Leave alone the busy injectors work.
Last edited by CaliBenzDriver; Feb 26, 2025 at 10:52 PM.
I'll be sure to take to MB dealer and specifically have them check for an update on the ECU. If they say there isn't one... you'd call BS?
I'd call that "du diligence"
The only thing that matter are RESULTS .... nothing else.
You have to take dealer's word do you make sure to ask properly....
To show you mean business, have dealer workout new coils + plugs + boots and update ECU.
When they get a bone, they may let you off the hook with that fix.
The flip side is you show up and ask for bare bone update work. They charge you $200 to say nope!
Everybody is plagued by the money milking misfires. It's Bosch design that helps rope business in.
Personally I will add MOD-4 to yield lag free mixtures near idle. This is the secret sauce disabled by low oil pressure solenoid...
Last edited by CaliBenzDriver; Feb 28, 2025 at 01:53 PM.
I already got the boots+plugs+coils replaced at the shop where i live.. i should of just taken it to the dealer. I did take it to the dealer when i first bought it. I would assume they wouldn't check the ecu for updates. I asked them to clear the command 5.5 so i could register it. when i called the dealer, he said it would be 240 to run the scan lol. you were right on the money. there isn't anyway a Indy shop can do that i assume? should i just go to the other MB dealer? appreciate the responses btw
I already got the boots+plugs+coils replaced at the shop where i live.. i should of just taken it to the dealer. I did take it to the dealer when i first bought it. I would assume they wouldn't check the ecu for updates. I asked them to clear the command 5.5 so i could register it. when i called the dealer, he said it would be 240 to run the scan lol. you were right on the money. there isn't anyway a Indy shop can do that i assume? should i just go to the other MB dealer? appreciate the responses btw
Of course any good MB indy shop can do that with a legit Xentry online account.
i'll post an update since most do not. received car back, new coils, plugs, boots, driven for a few days. smooth as butter. Now to get my rims fixed as i hit the biggest pot hole of my life. popped a tire and bent three rims... smh i've had all this happen in a matter of 5 months of owning the car. love the car. going to be upgrading the stereo to focal/JL audio with Helix V12 and JL audio 1200/1 on dual W7, and getting the windows tinted. I've never seen the amount of money people charge for window tint for this car. 800/900 for tint is wild. loved to get PPF as well like i had on the BMW.
i'll post an update since most do not. received car back, new coils, plugs, boots, driven for a few days. smooth as butter. Now to get my rims fixed as i hit the biggest pot hole of my life. popped a tire and bent three rims... smh i've had all this happen in a matter of 5 months of owning the car. love the car. going to be upgrading the stereo to focal/JL audio with Helix V12 and JL audio 1200/1 on dual W7, and getting the windows tinted. I've never seen the amount of money people charge for window tint for this car. 800/900 for tint is wild. loved to get PPF as well like i had on the BMW.
Congrats on getting your ignition reliable at once.
The huge pothole takes out more than just rims. control arms, ball joints, spindles, pited bearings and struts may be involved. Replace suspension parts BEFORE your wheel alignment.
See what sort of vibrations are left afterwards.
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