[Ch3ss]

i think you can get away with changing them in pairs since i change both my precat o2 sensors without changing out the after cats and my car didnt have any issues.

[Eleventeen]

I would just start with the rears.

[DefactoM6]

You can buy generic versions of the OEM O2 sensors which are identical to OEM except that you need to splice them in (whereas the OEM ones have a plug on them). Price savings are significant.

That said, I'm not fully convinced that a rear O2 sensor is the cause of your problems. While the full workings of the MSD80/81 misfire detection aren't fully known, what is known is that the front O2 sensors are primarily responsible for things relating to fueling/misfire detection in the engine, and that the primary reason for the rear O2 sensors existence is to ensure the function of the emissions control equipment. While we can't say for sure that the manner in which a rear o2 fails wouldn't trigger misfires, based on the current understanding of the misfire detection system, any actual misfires would be detected by the front o2 sensor, which would make your rear sensors somewhat irrelevant in the equation. That said, if there was something wrong with your O2s, you will 100% get codes for the O2s. However, it will not necessarily cause misfires. I should also mention that the bang you're hearing out of your exhaust is the sound of unburned fuel igniting somewhere in your exhaust. Which is what happens when the car either has an actual misfire, or THINKS it has a misfire and cuts ignition to the cylinder, sending unburned fuel out of the cylinder and into the exhaust, where it's igniting.

We do need more information, however. When does the car go into limp? Full load? At what RPM exactly? We need to know full conditions under which it happens. WOT? Gear? RPM? Ambient conditions?

Without knowing any of the above, and knowing that you have ~50k without ever being cleaned, my first bet is carbon. Cyl 4/5 is certainly indicative of it, and the fact that you get intermittent misfires in the front bank doesn't hurt either. However, being that you are a 6MT, and depending on the conditions under which you are misfiring, there is a possibility that you have a failing DMFW. We would need to know more to figure this out, however.

[psmitty95]

Originally Posted by aflyrice

i think you can get away with changing them in pairs since i change both my precat o2 sensors without changing out the after cats and my car didnt have any issues.

Ok that's good to know. Thanks

Originally Posted by Eleventeen

I would just start with the rears.

Thanks

Originally Posted by DefactoM6

You can buy generic versions of the OEM O2 sensors which are identical to OEM except that you need to splice them in (whereas the OEM ones have a plug on them). Price savings are significant.

That said, I'm not fully convinced that a rear O2 sensor is the cause of your problems. While the full workings of the MSD80/81 misfire detection aren't fully known, what is known is that the front O2 sensors are primarily responsible for things relating to fueling/misfire detection in the engine, and that the primary reason for the rear O2 sensors existence is to ensure the function of the emissions control equipment. While we can't say for sure that the manner in which a rear o2 fails wouldn't trigger misfires, based on the current understanding of the misfire detection system, any actual misfires would be detected by the front o2 sensor, which would make your rear sensors somewhat irrelevant in the equation. That said, if there was something wrong with your O2s, you will 100% get codes for the O2s. However, it will not necessarily cause misfires. I should also mention that the bang you're hearing out of your exhaust is the sound of unburned fuel igniting somewhere in your exhaust. Which is what happens when the car either has an actual misfire, or THINKS it has a misfire and cuts ignition to the cylinder, sending unburned fuel out of the cylinder and into the exhaust, where it's igniting.

We do need more information, however. When does the car go into limp? Full load? At what RPM exactly? We need to know full conditions under which it happens. WOT? Gear? RPM? Ambient conditions?

Without knowing any of the above, and knowing that you have ~50k without ever being cleaned, my first bet is carbon. Cyl 4/5 is certainly indicative of it, and the fact that you get intermittent misfires in the front bank doesn't hurt either. However, being that you are a 6MT, and depending on the conditions under which you are misfiring, there is a possibility that you have a failing DMFW. We would need to know more to figure this out, however.

Ehh I would much rather buy the bosch ones that plug right in. Cheaper than BMW ones but same thing. The code isn't appearing 100% of the time but does appear most as you can see from the pictures i've put up in this thread. Before the easiest way to get the car to misfire would be to do a pull starting from a stop with traction off 1-2nd gear. Usually that would trigger the misfire codes. Over the last few days though they've been coming on relatively easy. I could just be cruising at 40 then downshift to third and go to pass someone and boom, misfire and stumbling. I didn't drive the car today but did replace the plugs so i'll go out tomorrow and see if its still misfire which i'm sure it will be. Oddly enough yesterday was tough to get the car to misfire. On my way home from school I did my usual 3rd and 4th gear pulls to trigger the misfire but it wouldn't... It would stumble once or twice during the pull but not trigger a code... I even drove past my house to keep trying and went up a hill in 4th, 6th gear pull from 40, etc... I finally gave up and started heading home then right before my house did a quick third gear pull and sure enough I got the codes. Yesterday were misfires cyl 4,5,6. I'll post up pics of the plugs in a bit

[psmitty95]

Grabbed some quick pics of the plugs. 1-6 from left to right. Sorry the pics aren't great it was pretty dark outside... I'll try to grab some better ones tomorrow. Anyways I definitely don't think plugs were the issue since they look like they're in pretty good shape

[themyst]

You sure those plugs got 8k miles on them? You have a good amount of electrode wear. I'm willing to bet that's why your car's misfiring.

My plugs at 32k miles looked better than that. Compare the electrode wear of my plugs at 32k miles vs yours at 8k. I replaced valve cover gasket after seeing the oily cylinder 6, but I never misfired like you.

[E90Company]

Those plugs are worn out for 8k. Also your cyl 4 is pretty dark.

[Eleventeen]

Originally Posted by DefactoM6

You can buy generic versions of the OEM O2 sensors which are identical to OEM except that you need to splice them in (whereas the OEM ones have a plug on them). Price savings are significant.

That said, I'm not fully convinced that a rear O2 sensor is the cause of your problems. While the full workings of the MSD80/81 misfire detection aren't fully known, what is known is that the front O2 sensors are primarily responsible for things relating to fueling/misfire detection in the engine, and that the primary reason for the rear O2 sensors existence is to ensure the function of the emissions control equipment. While we can't say for sure that the manner in which a rear o2 fails wouldn't trigger misfires, based on the current understanding of the misfire detection system, any actual misfires would be detected by the front o2 sensor, which would make your rear sensors somewhat irrelevant in the equation. That said, if there was something wrong with your O2s, you will 100% get codes for the O2s. However, it will not necessarily cause misfires. I should also mention that the bang you're hearing out of your exhaust is the sound of unburned fuel igniting somewhere in your exhaust. Which is what happens when the car either has an actual misfire, or THINKS it has a misfire and cuts ignition to the cylinder, sending unburned fuel out of the cylinder and into the exhaust, where it's igniting.

We do need more information, however. When does the car go into limp? Full load? At what RPM exactly? We need to know full conditions under which it happens. WOT? Gear? RPM? Ambient conditions?

Without knowing any of the above, and knowing that you have ~50k without ever being cleaned, my first bet is carbon. Cyl 4/5 is certainly indicative of it, and the fact that you get intermittent misfires in the front bank doesn't hurt either. However, being that you are a 6MT, and depending on the conditions under which you are misfiring, there is a possibility that you have a failing DMFW. We would need to know more to figure this out, however.

Just a small correction: a backfire or popping could be caused by an actual misfire, but not a perceived misfire. When the DME thinks there is a misfire, it cuts spark AND fuel, so there wouldn't be popping. In fact, the whole point of misfire detection is to preserve the cats and prevent excess emissions from the unburnt fuel passing through; so the fuel is cut. This being the case, the popping signifies an actual misfire.

Also, not sure if the front O2 sensors help to detect misfires or not; but the primary detection is based on CPS feedback.

[psmitty95]

Originally Posted by E90Company

Those plugs are worn out for 8k. Also your cyl 4 is pretty dark.

Yea I noticed that cyl 4 was the darkest. Odd that they look that worn out

Originally Posted by themyst

You sure those plugs got 8k miles on them? You have a good amount of electrode wear. I'm willing to bet that's why your car's misfiring.

My plugs at 32k miles looked better than that. Compare the electrode wear of my plugs at 32k miles vs yours at 8k. I replaced valve cover gasket after seeing the oily cylinder 6, but I never misfired like you.

Well i'm at 56k now and the dealer said they replaced them at the 48k mile service... Hahaha I thought they looked decent but I guess not. I'll take a better pic later today

[sutter2k]

Originally Posted by joec500

I have had this intermittent cylinder 4-5-6 misfires forever. I have changed all my injectoes, both o2 sensors all my coilpacks and plugs. AND I still got them, so I inquired with my tech at FFTEC and he suggested checking the harness for my Procede. So I pulled out the patch that intercepts the fueling and o2's and disconnected and reconnected firmly and I haven't had the issues since. This actually makes senses because everytime I uninstalled my tune and re-installed it, it worked great for a few thousand miles, than all of sudden it would happen again.

I would check the patch that on the JB4 that intercepts the o2 ad fueling and maybe bend the pins a bit to get a better connection.

See if that helps and it doesn't cost anything.

ALSO I have had my cylinders cleaned out about 4k miles ago.

I believe I started to get this too. I disconnected and reconnected everything while adding a usb cable into the glove box so I could log what is going on. However, after reconnecting everything the issue has not come back. (obviously going with cobb would simplify this issue).

[Jeff@TopGearSolutions]

Those spark plugs look horrible for 8K. I call BS on the dealer changing them.

[joec500]

Originally Posted by Jeff@TopGearSolutions

Those spark plugs look horrible for 8K. I call BS on the dealer changing them.

+1, these are mine with 20k tuned miles, and a leaking injector #6

[iBoost]

Damn what a shady dealership those are definitely not 8k plugs. I'm guessing those are the original set if you've never changed them?

[SCS15]

I just changed mine at like 60k miles. Looked way cleaner than those.

[ken1137]

Damn, I'm gonna check my plugs next weekend. My dealer initially refused to change mine but acquiesced after I spoke to BMWNA and bitched. I forgot to ask for the old ones back.

OP...hope you get this resolved. I feel for you.

[psmitty95]

Originally Posted by Jeff@TopGearSolutions

Those spark plugs look horrible for 8K. I call BS on the dealer changing them.

I wouldn't put it past them, they are an awful dealer

Originally Posted by iBoost

Damn what a shady dealership those are definitely not 8k plugs. I'm guessing those are the original set if you've never changed them?

As I said above I wouldn't put it past them... My original service they gave me back the car with gum on the pedals, broken clips on the cowl, and they didn't do anything i requested (plugs, coils, injectors). Took it back and got them to do HPFP with video evidence and they claimed they did spark plugs. When I picked it up from that time they were wondering what my intake was so pulled it out and scratched it all over.... Said they would pay for a new pipe but never did.

Originally Posted by SCS15

I just changed mine at like 60k miles. Looked way cleaner than those.

Well it's definitely running smoother now that I changed them

Originally Posted by ken1137

Damn, I'm gonna check my plugs next weekend. My dealer initially refused to change mine but acquiesced after I spoke to BMWNA and bitched. I forgot to ask for the old ones back.

OP...hope you get this resolved. I feel for you.

Thanks man.







Quick update. So drove a bit today and everything seemed much better. When it was cold it was much smoother with less jerks accelerating gently. Mid day got the car warm and did a few short 2nd and 3rd bursts and all was good. I was ecstatic and thought the issue was finally fixed. Then as i'm driving I downshift to 2nd and go to pass someone and boom SES light and misfires... Checked coes and 2C7F Lambad probe behind catalytic converter 2, trimm control, 29D1 Cyl 5 misfire, 29D0 cyl 4 misfire. I did a restart then really pushed the car on the way home after the misfire and no hesitations. I was doing back roads and flooring it in 2nd, 3rd, etc... Only felt a slight hesitation once in 3rd but otherwise it was smooth and no misfires on the way home. Idk what to do anymore. The plugs definitely made it a bit smoother but still having the issues



P.S. Didn't get home until now so better pics of the plugs will hopefully be up tomorrow.

[drjekl]

Originally Posted by psmitty95

I wouldn't put it past them, they are an awful dealer



As I said above I wouldn't put it past them... My original service they gave me back the car with gum on the pedals, broken clips on the cowl, and they didn't do anything i requested (plugs, coils, injectors). Took it back and got them to do HPFP with video evidence and they claimed they did spark plugs. When I picked it up from that time they were wondering what my intake was so pulled it out and scratched it all over.... Said they would pay for a new pipe but never did.



Well it's definitely running smoother now that I changed them



Thanks man.







Quick update. So drove a bit today and everything seemed much better. When it was cold it was much smoother with less jerks accelerating gently. Mid day got the car warm and did a few short 2nd and 3rd bursts and all was good. I was ecstatic and thought the issue was finally fixed. Then as i'm driving I downshift to 2nd and go to pass someone and boom SES light and misfires... Checked coes and 2C7F Lambad probe behind catalytic converter 2, trimm control, 29D1 Cyl 5 misfire, 29D0 cyl 4 misfire. I did a restart then really pushed the car on the way home after the misfire and no hesitations. I was doing back roads and flooring it in 2nd, 3rd, etc... Only felt a slight hesitation once in 3rd but otherwise it was smooth and no misfires on the way home. Idk what to do anymore. The plugs definitely made it a bit smoother but still having the issues



P.S. Didn't get home until now so better pics of the plugs will hopefully be up tomorrow.

Time to try a new set of coils perhaps?

[ihc95]

Seems like you really push your car. I'm willing to bet the walnut blast will fix your issues. I also had mine done at Autocouture and things were definitely smoother. I didn't have any misfires or other issues with the car but I'm glad I got it done.

[psmitty95]

Originally Posted by drjekl

Time to try a new set of coils perhaps?

I don't think so I swapped cyl 4 and 5 coils to cyl 2 and 3 last week and the misfires didn't move.

Originally Posted by ihc95

Seems like you really push your car. I'm willing to bet the walnut blast will fix your issues. I also had mine done at Autocouture and things were definitely smoother. I didn't have any misfires or other issues with the car but I'm glad I got it done.

Hahaha I would say I drive it like its meant to be driven. Don't floor it all the time but when the opportunity presents itself I will have a little fun. If I didn't get the car for that I wouldn't be FBO with a suspension and whatnot. I'd say I probably drive as hard as the normal FBO 335 owner would. Walnut blasting is next on the list although it seems like plugs definitely helped. Walnut blasting will be May 18th

[AltecBX]

Yea I meant Autocouture in Fair Lawn.

From those pics on the plugs I don't believe they were changed 8k ago. If thats the case, either the dealer lied to you they changed it or they changed them with used ones. I can't see the plugs getting that bad in such short period of time, especially living in CT.

[marv85]

@psmitty95 , can you log after having changed plugs? I get the feeling you might be going lean

[psmitty95]

Originally Posted by AltecBX

Yea I meant Autocouture in Fair Lawn.

From those pics on the plugs I don't believe they were changed 8k ago. If thats the case, either the dealer lied to you they changed it or they changed them with used ones. I can't see the plugs getting that bad in such short period of time, especially living in CT.

Yea I definitely wouldn't put it past them

Originally Posted by marv85

@psmitty95 , can you log after having changed plugs? I get the feeling you might be going lean

Yea i'll do logs tomorrow. Just got home from a meet and put the car away for the night... I'll throw some up tomorrow but i'll also put up some logs from last week when I was logging for Terry. One of them was as the car was misfiring the others are just third gear pulls