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01-16-2022, 03:15 PM | #1 |
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S65 bank 2 misfire questions
Dear M3post, My M3 is having band 2 misfire issue. It happened suddenly one day at a traffic stop. The idling sounds rough and fluctuate a bit. After driving for a few more miles, the engine power reduce msg showed up on the screen. I was able to drive it back home. The car seems to be still drivable. (I don't drive it just in case). The car is e92 M3 at 53k miles no mode but m performance exhaust. I have searched our forum extensively. It seems that there is no definitive answer to this. I don't know where to start to debug the issue. I have replaced exhaust x pipe gaskets based on forum suggestion. What should I do next?
I have a basic scan tool. Here are a few codes: 2B41 Misfire with cutout several cylinders (spark plugs replaced 5K ago, ignition coils are original) 2B57 Air-mass sensor plausibility 2796 Throttle actuator test, lower stop (TAs have been replaced 5K miles ago) 27B1 Secondary air system flow rate bank2 2729 Oxygen sensor coast mode diagnosis before cat bank 2 (Both pre cat oxygen sensors were replaced (bosch version) about 3K miles ago) 2B39 Misfire with cutoff cyl. 5 6 7 8 2B4E Misfire impairing exhaust emission at several cylinders (I replaced the exhaust X pipe O ring gasket based on misfire forum search) Running data: Fuel injection timing cylinder 1-4: 3ms (at idle) or higher (when apply gas) Fuel injection timing cylinder 5-8: 0ms (at idle) stays at 0 (when apply gas)
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01-16-2022, 04:05 PM | #3 | |
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I pulled bank 2 Spark plugs out. They look OK. Previous owner replaced them 5K ago.
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01-16-2022, 04:15 PM | #4 | ||
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01-16-2022, 04:16 PM | #5 |
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If you have the means to do it, might be worth while to examine the cylinders for damage and do a compression and leakdown test.
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01-16-2022, 05:45 PM | #8 | |
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At the moment, I don't think there is any hydrolock or any damage the cylinder wall. I could be wrong. What is the sign of hydrolock?
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01-16-2022, 05:47 PM | #9 |
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These are the code after misfire happened. They are present codes.
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01-16-2022, 05:53 PM | #10 |
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I heard about grounding strap problem. I can look into it. I have put back an old oxygen sensor which doesn't seem to make any difference. For TAs, from what I can see on scan tool, they seem to work fine in terms of opening percentage.
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01-16-2022, 07:56 PM | #12 |
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You get all sorts of weird unrelated codes when your ground strap is toast. Happened to a friend of mine - misfires, TA codes, swapped stuff around, no change. Turned out it was the ground strap.
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01-16-2022, 09:17 PM | #13 | ||
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01-16-2022, 10:43 PM | #14 |
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Do you happen to know which ground strap was loose? There is one next to the downpipe I think. Is there one near bank 2?
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01-17-2022, 03:53 AM | #15 |
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01-17-2022, 07:48 AM | #16 |
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01-17-2022, 12:22 PM | #17 |
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Had the same rubbish happen to my car mate (codes and all). I replaced TAs, plugs, coils, the gasket rings from the headers back, and O2 sensors - nothing worked.
The culprit was the engine wiring harness. Replaced that and the car has run fine since. |
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01-17-2022, 02:36 PM | #18 |
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OK. So which engine harness was it replaced?
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03-13-2022, 03:33 PM | #19 |
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Update on my findings:
1. I have checked ground connections on bank 1 and 2. They look fine. I measured the ground resistance on injector connectors and ignition coil connector. They all seem to be in 0-1 ohm range. 2. Through reading engine information, it looks like all 8 cylinders run at the startup. After a few second (5-10sec), cylinder 8 fuel injector shut off. I can feel the start up is a bit rough. I think engine detects some misfire on cylinder 8 at startup and shut it off. My codes are pointing to 5,6,7,8 cylinders. But through reading the running engine data, it looks like cylinder 8. I swapped coil between 5 and 8 and spark plug between 5-8. It seems that cylinder 8 always got fuel cut off after 5-10sec of running. 3. I replaced all 4 injectors on bank 2 (5,6,7,8) with bosch OE part. It doesn't help. 4. I have also replaced bank 2 pre cat oxygen sensor with Bosch OE part. It doesn't help either. 5. Based on forum member suggestion, I bought compression kit and tested compression on bank 2. All 5, 6,7,8 are between 200psi to 210psi. To my surprise, their numbers are pretty consistent. 6. I have been thinking my car got broken valve spring, but based on compression test it doesn't look like. Should i consider a leak down test? Or use a borescope to inspect? At the moment, I am running out of ideas of how to further debug the problem. Should i buy a new coil for cylinder 8 to try? Let me know what you think. Thanks.
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03-13-2022, 07:41 PM | #21 |
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Are these codes still present?
2B57 Air-mass sensor plausibility 2796 Throttle actuator test, , lower stop 27B1 Secondary air system flow rate bank 2 2729 Oxygen sensor coast mode diagnosis before cat bank 2
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03-13-2022, 08:53 PM | #22 | |
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Actually, no, I haven't looked into this idle control valve. From the link you posted, it actually points to bent valve or broken spring. Should i look into adel control valve?
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