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)

I would be concerned about the fuel injectors and plugs I'd you're sure the o2 sensors aren't an issue and have no exhaust leaks.

spammysammich wrote

I would be concerned about the fuel injectors and plugs I'd you're sure the o2 sensors aren't an issue and have no exhaust leaks.

yes, I thought about injectors clogged. I took the injectors and fuel rail out and cranked the engine. By looking at the all 8 injectors, they are able to inject fuel in sequence. So it doesn't appear to be clogged.

I pulled bank 2 Spark plugs out. They look OK. Previous owner replaced them 5K ago.

aggieshan wrote

spammysammich wrote

I would be concerned about the fuel injectors and plugs I'd you're sure the o2 sensors aren't an issue and have no exhaust leaks.

yes, I thought about injectors clogged. I took the injectors and fuel rail out and cranked the engine. By looking at the all 8 injectors, they are able to inject fuel in sequence. So it doesn't appear to be clogged.

I pulled bank 2 Spark plugs out. They look OK. Previous owner replaced them 5K ago.

What about signs of injector leakage? Bore wash and hydrolock is a legitimate concern as well.

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.

Are those the present codes or codes that were there previously?

Injectors won't die 4 at a go. Check your grounding strap first. Also swap your O2 sensors left to right. Lastly swap your throttle actuators left to right. See if the problem follows.

spammysammich wrote

What about signs of injector leakage? Bore wash and hydrolock is a legitimate concern as well.

Not sure how to examine the leakage. From what I can see when I took fuel rail and injectors out, there were no fuel leaking from them. When i crank the car, the injectors work as what I expected.

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?

tdott wrote

Are those the present codes or codes that were there previously?

These are the code after misfire happened. They are present codes.

Redd wrote

Injectors won't die 4 at a go. Check your grounding strap first. Also swap your O2 sensors left to right. Lastly swap your throttle actuators left to right. See if the problem follows.

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.

aggieshan wrote

These are the code after misfire happened. They are present codes.

Why are there TA and O2 codes if you said those were changed? Something doesn't seem right or it wasn't fixed properly.

When you clear the codes which ones come back first and how soon?

tdott wrote

Why are there TA and O2 codes if you said those were changed? Something doesn't seem right or it wasn't fixed properly.

When you clear the codes which ones come back first and how soon?

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.

aggieshan wrote

spammysammich wrote

What about signs of injector leakage? Bore wash and hydrolock is a legitimate concern as well.

Not sure how to examine the leakage. From what I can see when I took fuel rail and injectors out, there were no fuel leaking from them. When i crank the car, the injectors work as what I expected.

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?

Basically if you have the rail/injectors out just prime the fuel pump without cranking it. Just build pressure in the system and see if any fuel leaks. Redd may be on to something with the grounds. All sorts of weird faults pop up when the ground strap is loose or perished.

Redd wrote

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.

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?

aggieshan wrote

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?

There is only the one next to the downpipe.

aggieshan wrote

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?

There is 2 small ones from the harness on each valve cover. Check those as those are the ones that would cause misfires.

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.

Yoddha wrote

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.

OK. So which engine harness was it replaced?

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.

Have you considered the idle control valve?

https://www.m3post.com/forums/showpost.php?p=20873306&postcount=4

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

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?

chenium wrote

Have you considered the idle control valve?

https://www.m3post.com/forums/showpost.php?p=20873306&postcount=4