Amgman1998

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





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 V8 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.

Jaydavid93

So It seems like after 35k miles or 5 years and or both. A lot of people get misfire on 1-5. I changed my spark plugs myself oem. Then a shop swapped the coils around and it still misfired. On the cylinder they swapped it too. MB needed to do software updates. They have a new one each year for our car if you have not got them and still have done the mechanical work chances are your gonna still have this problem. Hence why I went with a piggyback ecu. Turns out MB I bought the car from new still payed for a new coil since my miles were low. Granted I had to pay for the rail pressure sensor. But the firmware updates were free. Now she runs fine. Basically coils and plugs and sometimes the sensors are going to be shot. If you drive a tuned car or just drive hard in general. This is normal imo to have this issue. I noticed the plastic all under the hood has crumbled in a few years alone. The heat these motors make ruins the car fast. My advice is to get new spark plugs all 8 then whatever coils are misfiring on. Then check the sensors and whatnot. Take it to a dealer and get a loaner car for your trouble. Do the spark plugs yourself. And let them figure out which coils are bad. I learned with this car. Never waste time with small shops that don’t wish to spend weeks on finding the trouble. If you’re a close to 5 years old with no plugs coils or rail pressure sensors swapped I would say it’s time. Good luck

and ps you still need to take it to the dealer to update firmware after the swaps to 2023 firmware which will wipe out an ecu tune. Which is probably a ploy to get more money but it works don’t it? Lol

Jaydavid93

Also what codes are you scanning? I had p0190 rail sensor Cam sensor once even and cyilinder misfire the plugs helped a huge amount on the smoothness and power return don’t count them out yet.

ahmadshahzad1

Specifically a misfire on Cylinder 5. It's frustrating because I don't trust mechanics anymore after a series of bad experiences. They always seem to find additional problems that weren't there before. If you're ever in need of a reliable service, whether it's for car repairs or something completely different like a logo design Dubai, make sure to do thorough research and find someone you can trust. It can save you a lot of headaches in the long run.