Strange Misfire experience...any ideas?
08-25-2017, 12:03 AM
#1
Member
Thread Starter
Strange Misfire experience...any ideas?
I was driving my 2014 S550 4matic (73K miles) on the highway this evening and suddenly I had a shaking and shuddering with a dramatic loss of engine power and the Check Engine/MIL light came on. The shaking on the car was tremendous but I did make it home. I was reluctant to pull over as I was concerned the car may not start back up.
When I got home I shut the car down and tried to start it back up and it started immediately and the Check Engine/MIL light was out, and the car ran and idled fine. WTF?
I put my code reader into the OBDII port and got these codes:
I would have immediately thought that the car had a bad plug or coil, but for two cylinders to simultaneously misfire continually and go out at the same moment, and then for the problem to clear-up after a stop and restart...seems strange. I am doubting it's a bad coil(s) or plug(s) since they both occurred at the same time and after a simple restart the car runs fine (so far).
Anybody have any ideas of what may be the culprit cause and/or know if this is a known symptom of a known problem specific to this 4.6L turbo engine? On my previous (2010) S550 I had experienced a bad coil, but that problem did not resolve itself after a restart...and a quick replace of the indicated misfiring cylinder's coil resolved the problem (and then I replaced the other 7 to be on the safe side - and that didn't rear it's ugly head until 250K-miles.)
And can anyone indicate or provide a schematic of which/where the cylinder numbers is/are? I am assuming cylinders 7 and 8 are at the back of the engine...but I think it would be good to know which is which.
Many thanks in advance.
When I got home I shut the car down and tried to start it back up and it started immediately and the Check Engine/MIL light was out, and the car ran and idled fine. WTF?
I put my code reader into the OBDII port and got these codes:
- P0300 - Multiple Misfire Detected
- P0307 - Cylinder 7 Misfire
- P0308 - Cylinder 8 Misfire
I would have immediately thought that the car had a bad plug or coil, but for two cylinders to simultaneously misfire continually and go out at the same moment, and then for the problem to clear-up after a stop and restart...seems strange. I am doubting it's a bad coil(s) or plug(s) since they both occurred at the same time and after a simple restart the car runs fine (so far).
Anybody have any ideas of what may be the culprit cause and/or know if this is a known symptom of a known problem specific to this 4.6L turbo engine? On my previous (2010) S550 I had experienced a bad coil, but that problem did not resolve itself after a restart...and a quick replace of the indicated misfiring cylinder's coil resolved the problem (and then I replaced the other 7 to be on the safe side - and that didn't rear it's ugly head until 250K-miles.)
And can anyone indicate or provide a schematic of which/where the cylinder numbers is/are? I am assuming cylinders 7 and 8 are at the back of the engine...but I think it would be good to know which is which.
Many thanks in advance.
08-25-2017, 08:16 AM
#2
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Join Date: Mar 2017
Location: Birmingham, AL
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2019 S560, 2022 Audi S8
I was driving my 2014 S550 4matic (73K miles) on the highway this evening and suddenly I had a shaking and shuddering with a dramatic loss of engine power and the Check Engine/MIL light came on. The shaking on the car was tremendous but I did make it home. I was reluctant to pull over as I was concerned the car may not start back up.
When I got home I shut the car down and tried to start it back up and it started immediately and the Check Engine/MIL light was out, and the car ran and idled fine. WTF?
I put my code reader into the OBDII port and got these codes:
Anybody have any ideas of what may be the culprit cause and/or know if this is a known symptom of a known problem specific to this 4.6L turbo engine? On my previous (2010) S550 I had experienced a bad coil, but that problem did not resolve itself after a restart...and a quick replace of the indicated misfiring cylinder's coil resolved the problem (and then I replaced the other 7 to be on the safe side - and that didn't rear it's ugly head until 250K-miles.)
And can anyone indicate or provide a schematic of which/where the cylinder numbers is/are? I am assuming cylinders 7 and 8 are at the back of the engine...but I think it would be good to know which is which.
Many thanks in advance.
When I got home I shut the car down and tried to start it back up and it started immediately and the Check Engine/MIL light was out, and the car ran and idled fine. WTF?
I put my code reader into the OBDII port and got these codes:
- P0300 - Multiple Misfire Detected
- P0307 - Cylinder 7 Misfire
- P0308 - Cylinder 8 Misfire
Anybody have any ideas of what may be the culprit cause and/or know if this is a known symptom of a known problem specific to this 4.6L turbo engine? On my previous (2010) S550 I had experienced a bad coil, but that problem did not resolve itself after a restart...and a quick replace of the indicated misfiring cylinder's coil resolved the problem (and then I replaced the other 7 to be on the safe side - and that didn't rear it's ugly head until 250K-miles.)
And can anyone indicate or provide a schematic of which/where the cylinder numbers is/are? I am assuming cylinders 7 and 8 are at the back of the engine...but I think it would be good to know which is which.
Many thanks in advance.
Might be water in the fuel system/tank.
08-25-2017, 09:11 AM
#3
Mine did the same thing. Dealer scanned it and stated one of the injectors had been misfiring and was defective and replaced it. Acceleration is now noticeably more silky smooth
I was driving my 2014 S550 4matic (73K miles) on the highway this evening and suddenly I had a shaking and shuddering with a dramatic loss of engine power and the Check Engine/MIL light came on. The shaking on the car was tremendous but I did make it home. I was reluctant to pull over as I was concerned the car may not start back up.
When I got home I shut the car down and tried to start it back up and it started immediately and the Check Engine/MIL light was out, and the car ran and idled fine. WTF?
I put my code reader into the OBDII port and got these codes:
I would have immediately thought that the car had a bad plug or coil, but for two cylinders to simultaneously misfire continually and go out at the same moment, and then for the problem to clear-up after a stop and restart...seems strange. I am doubting it's a bad coil(s) or plug(s) since they both occurred at the same time and after a simple restart the car runs fine (so far).
Anybody have any ideas of what may be the culprit cause and/or know if this is a known symptom of a known problem specific to this 4.6L turbo engine? On my previous (2010) S550 I had experienced a bad coil, but that problem did not resolve itself after a restart...and a quick replace of the indicated misfiring cylinder's coil resolved the problem (and then I replaced the other 7 to be on the safe side - and that didn't rear it's ugly head until 250K-miles.)
And can anyone indicate or provide a schematic of which/where the cylinder numbers is/are? I am assuming cylinders 7 and 8 are at the back of the engine...but I think it would be good to know which is which.
Many thanks in advance.
When I got home I shut the car down and tried to start it back up and it started immediately and the Check Engine/MIL light was out, and the car ran and idled fine. WTF?
I put my code reader into the OBDII port and got these codes:
- P0300 - Multiple Misfire Detected
- P0307 - Cylinder 7 Misfire
- P0308 - Cylinder 8 Misfire
I would have immediately thought that the car had a bad plug or coil, but for two cylinders to simultaneously misfire continually and go out at the same moment, and then for the problem to clear-up after a stop and restart...seems strange. I am doubting it's a bad coil(s) or plug(s) since they both occurred at the same time and after a simple restart the car runs fine (so far).
Anybody have any ideas of what may be the culprit cause and/or know if this is a known symptom of a known problem specific to this 4.6L turbo engine? On my previous (2010) S550 I had experienced a bad coil, but that problem did not resolve itself after a restart...and a quick replace of the indicated misfiring cylinder's coil resolved the problem (and then I replaced the other 7 to be on the safe side - and that didn't rear it's ugly head until 250K-miles.)
And can anyone indicate or provide a schematic of which/where the cylinder numbers is/are? I am assuming cylinders 7 and 8 are at the back of the engine...but I think it would be good to know which is which.
Many thanks in advance.
08-25-2017, 09:56 AM
#4
Member
Thread Starter
My local Mercedes-Benz service manager advised:
It is possible that something happened for a misfire on those 2 cylinders (dirt in injector) and when it happens it shuts down those cylinders until the key is recycled. Other than that we do not have any common concerns for this engine. Let me know if I can be of any assistance.
