Engine misfiring (2016 w205 C63S) help

[Amgman1998]

Car: 2016 Mercedes w205 C63 AMG S saloon. 4.0L v8


What happened

• Car was misfiring once while in garage while low on fuel. Was refueled, left alone for a day and turned on without a misfire.

• Took car home, after a week, misfired again and engine management light came on. The misfire was quite bad, car was very juddery, especially when accelerating, and the car much louder than usual, even without the sport exhaust on.

• Left car alone for a week before taking to my mechanic. Mechanic diagnosed misfiring on cylinder 5 & 6. Mechanic swapped around the spark plugs with cylinders on 1 & 2 to see if misfiring swapped sides. No difference. He then swapped the ignition coils over, and the misfiring DID swap sides, to cylinders 1 & 2. He said it must be my coils and i was instructed to order a new one.

What was done:

• I ordered a new ignition coil along with 2 new spark plugs (Mercedes AMG V8 C63S so each coil has 2 plugs) just incase.

• Took car back to the garage, where all was fitted.

• Now, just cylinder 2 is misfiring.

• My mechanic once again swapped the coil from 1 & 2 to the side with 5 & 6. The misfire was now back on cylinder 5.

• Mechanic suspects the coil was either not new or part damaged and instructed to try buy another one.

Where im at now:

• I followed my mechanics instructions, and sourced a 2nd replacement coil (Used in this case). The misfire is the same, just on one cylinder, and still follows suit when we swap it over to the other side of the engine.

• I am starting to believe that the chances of me ordering not 1 bad coil, but 2, is very unlikely. I would order brand new from Mercedes, but they’re on back order with an estimated 4 month wait. Theres another for sale i can buy tomorrow, but is there any point?

• The car does not run terribly, but it does judder a bit when accelerating at low revs, and also occasionally drops power for half a second before regaining. I have not driven the car hard while in this state. It is not as loud any more on start up or while running it, as it was when there was 2 cylinders misfiring.

• In my head I’ve ruled out the spark plugs. Question is, what are my options? Try one final replacement ignition coil? What else could the issue be? Fuel injectors? I just want the car running at 100% again and im fed up to be honest. Ive been reading a million different things and losing my head over what to do next

• I should add, i am not being charged any labour from this mechanic, as he and my father were very good friends and my dad did him many big favours in the past, so he is not shafting me for cash, and the quicker this gets fixed, the better it is for him.

• Sorry for the long post, any suggestions or insights would be greatly appreciated

 

[Jobsworth]

I think I have a couple of known good coils on the shelf I’d be happy to let you try. I’m not back in my shop until Friday, but I’m there Saturday morning too if it would help you

 

[Amgman1998]

I think I have a couple of known good coils on the shelf I’d be happy to let you try. I’m not back in my shop until Friday, but I’m there Saturday morning too if it would help you

Would be much appreciated. Are they the correct ones, as i’d be coming from london. You reckon could be something other than the coils at all causing the misfire? Thanks for the quick response

 

[Jobsworth]

They are m177. Let me check Friday morning, but I’m sure they are there. I’ll post up the part number so you can check, but they are the right ones.
There are a couple of other finicky things with ‘em, but if your misfire moved with the coils it’s a big tell.

 

[Jobsworth]

I used them on a car with a misfire on 1 and 6, but it didn’t fix it so I took them off again. It’s long story to type out, but that was a software issue. 1 and 6 are both at tdc at the same time. The camshaft position dictates which of the two is on its firing stroke. There was a software glitch on some early cars that couldn’t identify which was which everytime, and misfires on those two cylinders would be recorded. I fixed it in the end.

 

[Amgman1998]

I used them on a car with a misfire on 1 and 6, but it didn’t fix it so I took them off again. It’s long story to type out, but that was a software issue. 1 and 6 are both at tdc at the same time. The camshaft position dictates which of the two is on its firing stroke. There was a software glitch on some early cars that couldn’t identify which was which everytime, and misfires on those two cylinders would be recorded. I fixed it in the end.

No worries, and yeah M177 is correct im pretty certain, part number ends in 500 i believe.

Could you pm me where your shop is? And how much youd like for the coil if it sorts the issue?

And i guess if the misfire is following the coil is telling as you & my mechanic have said, i could really have just been unlucky with two! I just found it almost hard to believe one could buy two non functioning coils in a row!

 

[badgx]

I used them on a car with a misfire on 1 and 6, but it didn’t fix it so I took them off again. It’s long story to type out, but that was a software issue. 1 and 6 are both at tdc at the same time. The camshaft position dictates which of the two is on its firing stroke. There was a software glitch on some early cars that couldn’t identify which was which everytime, and misfires on those two cylinders would be recorded. I fixed it in the end.

How did you fix it buddy, did it need a software update?

 

[Jobsworth]

How did you fix it buddy, did it need a software update?

Yes. All the update does is give it a small throttle kick on cranking. The engine speed as it fires was too low, and it couldn’t reliably tie together the camshaft sensor and crankshaft sensor signals to identify cylinder 1 at tdc on the firing stroke. You could avoid the fault yourself if you applied throttle while starting it. It was so obvious in the end, but it took a couple of weeks to resolve it.

 

[Jobsworth]

Bizarrely all it gave you was fault codes for misfire on cylinders 1 and 6. Nothing about cam/crank sensor correlation. If it had I’d have been straight on it.

 

[badgx]

Yes. All the update does is give it a small throttle kick on cranking. The engine speed as it fires was too low, and it couldn’t reliably tie together the camshaft sensor and crankshaft sensor signals to identify cylinder 1 at tdc on the firing stroke. You could avoid the fault yourself if you applied throttle while starting it. It was so obvious in the end, but it took a couple of weeks to resolve it.

That would puzzle most mechanics I think Thank god there is a software update, and great to hear its sorted

 

[Jobsworth]

I’m at RH14 9DE. Business is ACE Engineering.

Does you fault only occur as you start the car? If it starts clear does it run ok? Get your man to confirm which cylinders are faulting. If it’s 1 and 6 it could be what ive seen before

 

[Amgman1998]

I’m at RH14 9DE. Businesses is ACE Engineering.

Does you fault only occur as you start the car? If it starts clear does it run ok? Get your man to confirm which cylinders are faulting. If it’s 1 and 6 it could be what ive seen before

Got you, thanks, friday lunchtime/afternoon? The fault occurs and maintains from when i start the car, throughout any journey, until turned off.

Right now, just cylinder 5. If we swap over the coil to the other side, it becomes a cylinder 2 misfire

 

[Jobsworth]

Got you, thanks, friday lunchtime/afternoon? The fault occurs and maintains from when i start the car, throughout any journey, until turned off.

Right now, just cylinder 5. If we swap over the coil to the other side, it becomes a cylinder 2 misfire

Worth trying another coil for sure. I’ll post up here Friday morning to confirm what I have

 

[Amgman1998]

Worth trying another coil for sure. I’ll post up here Friday morning to confirm what I have

Absolute life saver appreciate all the input. Given me a bit of confidence. Owned several different mercedes including the 5.5l s63 coupe and none have given me even close to the grief this C class has! Hopefully the last time

 

[Jobsworth]

Yup, got 2 here

 

[Jobsworth]

2

 

[Amgman1998]

2
View attachment 141666

Great news thanks, i’ll make way in 30 mins, takes me about 1 hour 15 to get to you

 

[Jobsworth]

I have to go out for an MoT. Back here about 13.30. If I’m not here just wait, I won’t be long

 

[Jobsworth]

OP turned up this afternoon and I replaced the errant coil for him. Job appears to be a good’un

 

[badgx]

OP turned up this afternoon and I replaced the errant coil for him. Job appears to be a good’un

Another member rescued