Misfiring Cylinders 3, 6, 7
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Misfiring Cylinders 3, 6, 7
I need more brains to help me figure out why my 2013 C63 is misfiring on cylinders 3, 6, 7. It started misfiring on me one day while idling at a red light. After I got the car home, I found one very obviously burnt and slightly melted coil pack in cylinder #5. I replaced that one coil pack with an AutoZone coil pack while I was waiting for a Mercedes one to get shipped, but noticed that now i'm getting misfires in other cylinders as well.
Things i've tried so far:
Can someone help me find a wiring diagram for the coil pack connector and help me trace it back to the ECU so I can double check each pin in more detail. When I checked the harness earlier I just verified each coil pack had 12v and ground and had continuity to the ECU harness.
Things i've tried so far:
- Changed all coil packs to brand new Mercedes AMG coil packs
- Changed all spark plugs to brand new NGK spark plugs
- Changed all fuel injectors to brand new Bosch factory-spec fuel injectors
- Unplugged the MAF, still misfires
- Unplugged one bank of cam sensors, still misfires
- Swapped around coil packs, still misfires on the same cylinders
- Swapped around spark plugs, still misfires on the same cylinders
- Traced the wiring for all 8 coil packs back to the ECU harness and verified it was fine
- Sent the ECU to a local ECU test and repair centre, which said I had damaged ignition drivers and they swapped out the ignition driver but it still misfires on the same cylinders
Can someone help me find a wiring diagram for the coil pack connector and help me trace it back to the ECU so I can double check each pin in more detail. When I checked the harness earlier I just verified each coil pack had 12v and ground and had continuity to the ECU harness.
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Just keeping an ongoing tally of things i've tried:
20241103 - Cleaning all four cam position sensors, didn't get to crank position sensor. Exhaust cam position sensors had some silver sludge on them. Wiped it all off, tried starting. Still has a miss on 3, 6, 7. Tried unplugging passenger side exhaust bank. Still misfires. Plugged in passenger side and unplugged driver's side exhaust bank. Still misfires.
20241103 - Cleaning all four cam position sensors, didn't get to crank position sensor. Exhaust cam position sensors had some silver sludge on them. Wiped it all off, tried starting. Still has a miss on 3, 6, 7. Tried unplugging passenger side exhaust bank. Still misfires. Plugged in passenger side and unplugged driver's side exhaust bank. Still misfires.
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Oil looks fine, no mixing of coolant and oil. While checking and cleaning my cam position sensors, I noticed some silver paste that was probably fine ferrous metal that had collected around the hall sensor. That's the only oddity I found in the oil so far:
Last edited by 0fc5dccf; Nov 5, 2024 at 01:01 PM.
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Here's me quadruple checking the wiring harness again. I checked all eight coil packs, all four pins for power and ground, and also traced the signal wires back to the ECU and the confirmation wire which I think Mercedes is just tying to ground. Also checked all of the ground points bolted to the heads and I did find a loose ground on the driver's side bolt near the cam control solenoids. I tightened that ground up but it didn't make a difference. Also checked the capacitors on each head that looks like it's being used as a noise filter. Everything checks out.
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Around 406kpa, which is normal at idle
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W213 All-terrain
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Yes, taking apart the intake manifold and checking for leaks is going to be eventually down the line, but how does intake manifold prevent the coil plug from igniting? The main issue here is a lack of spark signal from the ECU.
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W204
if you've confirmed everything is sound to and from the ECU and still not getting spark on those cylinders, i'd say there's an issue with the ECU. i know you sent it out once, but maybe get a second opinion on it elsewhere?
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If you trust the diag machine,
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They don't think the ECU can be repaired, or at the worst case they can attempt repair but can't guarantee the repair will work. I'm shopping for a new ECU right now.
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Aftermarket shops can clone the contents of the old ECU to the new ECU, as long as the ECU memory is readable. Both of the shops I worked with are able to perform this service for about $150.
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2006 E55
It is definitely not drop-in plug and play. The ECU is considered a theft-relevant part and can only be ordered in person at the dealership with ID check. After it is ordered it needs to be coded for the car before it can be used.
Aftermarket shops can clone the contents of the old ECU to the new ECU, as long as the ECU memory is readable. Both of the shops I worked with are able to perform this service for about $150.
Aftermarket shops can clone the contents of the old ECU to the new ECU, as long as the ECU memory is readable. Both of the shops I worked with are able to perform this service for about $150.
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I don't have any ill will towards them. I dropped off the ECU and was very clear to them that I had no rush for any of this and mistakes happen, I've already spoken to the owner and he assures me he will personally take care of it.
https://maps.app.*******/BSd9Bck42khPdrhTA
Second shop where I got a second opinion where they confirmed the coil pack drivers were bad:
This place charged me $40 just to run the ECU on their test machine, which confirmed that no ignition signal was being sent out.
https://maps.app.*******/Bab3A5RTuYHkCDb36
Right now the car is waiting on ARP cam bridge bolts and "Stage 1" cams from 63Motorsports, which are currently backordered until early next year so I don't have a rush to get this fixed right now. I'll keep you guys updated on what's going on.
edit: looks like I can't paste Google Maps links here? First one is TRN Electronics, second one is 1800ECM. Both are in the greater Houston area.
Last edited by 0fc5dccf; Dec 10, 2024 at 10:18 AM.
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2006 E55
First shop I went to.
I don't have any ill will towards them. I dropped off the ECU and was very clear to them that I had no rush for any of this and mistakes happen, I've already spoken to the owner and he assures me he will personally take care of it.
https://maps.app.google.com/BSd9Bck42khPdrhTA
Second shop where I got a second opinion where they confirmed the coil pack drivers were bad:
This place charged me $40 just to run the ECU on their test machine, which confirmed that no ignition signal was being sent out.
maps.app.google.com/Bab3A5RTuYHkCDb36
Right now the car is waiting on ARP cam bridge bolts and "Stage 1" cams from 63Motorsports, which are currently backordered until early next year so I don't have a rush to get this fixed right now. I'll keep you guys updated on what's going on.
I don't have any ill will towards them. I dropped off the ECU and was very clear to them that I had no rush for any of this and mistakes happen, I've already spoken to the owner and he assures me he will personally take care of it.
https://maps.app.google.com/BSd9Bck42khPdrhTA
Second shop where I got a second opinion where they confirmed the coil pack drivers were bad:
This place charged me $40 just to run the ECU on their test machine, which confirmed that no ignition signal was being sent out.
maps.app.google.com/Bab3A5RTuYHkCDb36
Right now the car is waiting on ARP cam bridge bolts and "Stage 1" cams from 63Motorsports, which are currently backordered until early next year so I don't have a rush to get this fixed right now. I'll keep you guys updated on what's going on.
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10 C six trizzle
Ecu seems likely, or a loose / bad ground. You should also go ahead and do a compression and leak down test. You never know. Wasting a lot of money and time on electronics when it could be a mechanical issue. Sure unlikely to have that occur on 3 cylinders, but those maybe the ones showing issues first, or the ecu is interpreting them inaccurately.
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Ecu seems likely, or a loose / bad ground. You should also go ahead and do a compression and leak down test. You never know. Wasting a lot of money and time on electronics when it could be a mechanical issue. Sure unlikely to have that occur on 3 cylinders, but those maybe the ones showing issues first, or the ecu is interpreting them inaccurately.
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Some updates - I mailed the ECU to ECU Pros, who confirmed that someone had replaced components, but did a poor and incomplete job so the original fault was never repaired correctly. They said they were confident in being able to repair the ECU so I paid them ~$400.
A week later I got the ecu back and did more testing. I now have spark on all 8 cylinders, but now i'm not having fuel in cylinder #3. I was able to confirm this by checking the injectors with a hall effect sensor, and also by swapping out injectors - somewhere now the ECU is not sending an injector pulse to cylinder #3.
In the meantime I have sent the ECU back to ECU Pros to have them inspect the injector drivers and see what's going on - will update when I get the ECU back.
A week later I got the ecu back and did more testing. I now have spark on all 8 cylinders, but now i'm not having fuel in cylinder #3. I was able to confirm this by checking the injectors with a hall effect sensor, and also by swapping out injectors - somewhere now the ECU is not sending an injector pulse to cylinder #3.
In the meantime I have sent the ECU back to ECU Pros to have them inspect the injector drivers and see what's going on - will update when I get the ECU back.
