I have just been looking at another log from yesterday where the LTFRs increase with revs and drop back to 0 at idle. From the information that I have read this indicates a fuel flow or MAP/MAF sensor issue. However, the rail pressure is remaining high during the log although the AFRs are running lean. Can the HPFP have high pressure but low flow? I have changed the MAP and MAF sensors before without change but I will clean them again and see if anything changes.
Intermittent misfire
- Thread starter Coupes66
- Start date
Why is the accel pedal bouncing around like that? Also log fuel mode in future as it helps when troubleshooting.I have just been looking at another log from yesterday where the LTFRs increase with revs and drop back to 0 at idle. From the information that I have read this indicates a fuel flow or MAP/MAF sensor issue. However, the rail pressure is remaining high during the log although the AFRs are running lean. Can the HPFP have high pressure but low flow? I have changed the MAP and MAF sensors before without change but I will clean them again and see if anything changes.
The accel pedal is bouncing around from me pumping the accelerator trying to prevent the engine from shutting down so I could get a log. Thanks for the tip about fuel mode. I will log it next time.
I still haven't sorted out the problem with my engine. I have installed new injectors in the last couple of days which have improved the situation. Since this problem started, a couple of months ago, I have installed new plugs, new oxy sensors, new MAP sensor, new MAF sensor, and new fuel rail pressure sensor. On cold start, the engine still pops and misses a bit until it gets down to idle at 700rpm and then it idles ok. The datalogs at idle are showing negative LTFRs in the 10-15% range although the AFRs and STFTs are looking fine. Once the revs are increased to 1,700 rpm, the LTFTs go back to around -3% which is ok. What could be the cause of the -10 to 15% LTFTs at idle? Attached are some of the datalogs.
datazap.me | Coupes44 | Datalog.050423
datazap.me | Coupes44 | Datalog.050423.1
datazap.me | Coupes44 | Datalog.040423.2
datazap.me | Coupes44 | Datalog.050423
datazap.me | Coupes44 | Datalog.050423.1
datazap.me | Coupes44 | Datalog.040423.2
I am by no means an expert on the platform…full disclosure. There are some very experience folks here that are way smarter than me but I’ll take a stab.
Sounds like you’ve focused on a hardware issue. Also looks like a custom tune. Was the tune working well prior to the issue and for how long. Maybe a fuel delivery problem. Have you tried adjusting fuel scalars and cold start tables? Have you tried a wider gap on the plugs. Does the car run well flashed back to stock?
Sounds like you’ve focused on a hardware issue. Also looks like a custom tune. Was the tune working well prior to the issue and for how long. Maybe a fuel delivery problem. Have you tried adjusting fuel scalars and cold start tables? Have you tried a wider gap on the plugs. Does the car run well flashed back to stock?
A short time after completing the previous post, I drove the car to the dump/refuge. On starting the car, there was an intermittent miss which was apparent while driving out to the dump. At the dump, I turned off the engine. When I started the engine to come home, the miss had worsened to a point that it was difficult to keep the engine running. The engine light came on with missfires on all cylinders. I cleared the codes while driving and got it home with a lot of difficulty. The logs show the AFRs going from lean to rich in big swings sometimes out of sync with each other. The STFTs don't appear to be reacting to the AFRs quickly or correctly. When the AFRs are extra rich, the STFTs are still positive when they should be instantaneously going into the negative. Yesterday, I took it for a 10km run without an issue while today, it is a disaster. I should have left it at the dump. At a guess, I would say the immediate issue is the plugs are fouled from too much fuel and will require cleaning. What is causing the fueling problem, I don't know.
Log from yesterday
datazap.me | Coupes44 | Datalog.050423.2
Log while waiting at dump weigh bridge today
datazap.me | Coupes44 | Datalog.060423
Log after arriving home from dump today
datazap.me | Coupes44 | Datalog.060423.1
Log from yesterday
datazap.me | Coupes44 | Datalog.050423.2
Log while waiting at dump weigh bridge today
datazap.me | Coupes44 | Datalog.060423
Log after arriving home from dump today
datazap.me | Coupes44 | Datalog.060423.1
Thanks for your reply. The custom tune is from Ken Atkinson (Wedge) which I have run for a few months without an issue before this problem began so that is the reason I have been chasing down a hardware fault. The LPFPs maintain 72+psi so I don't see a problem there and it has handled 100% E85 with no issue in the past. Currently, I am running on BP98 fuel. The HPFP has been running around the 700+psi at idle but does drop momentarily to mid 600s at times. I have a new HPFP on order just to cover all bases. I am running NGK 97968 Laser Iridium plugs gapped to 0.018".
I would ask ken to look into the issue. You’ve changed out quite a few parts. If nothing else then you’ve at least adjusted the tune to your new parts. This really sounds like a software issue to me (again I’m not an expert and simply trying to draw conclusions based on my experience which likely ain’t worth a damn and the info you’ve provided).
I’m wondering if you’ve got an issue with your fuel injection. Not your injectors but your spray flow characteristics vs what the map and logic likes.
I’d also like to know how the hpfp contributes to the logic other than proving a target psi. I think there are several tables controlling the performance aside from just pressure and I also don’t think we (enthusiasts) have the tables or algorithms to see what’s going on. Not that I’ve searched but the only hpfp/vcv tables I’ve seen are pretty random.
from a tuning perspective, you may consider reaching out to carabuser as he is relatively active here and very knowledgeable from the threads I’ve read.
I’m wondering if you’ve got an issue with your fuel injection. Not your injectors but your spray flow characteristics vs what the map and logic likes.
I’d also like to know how the hpfp contributes to the logic other than proving a target psi. I think there are several tables controlling the performance aside from just pressure and I also don’t think we (enthusiasts) have the tables or algorithms to see what’s going on. Not that I’ve searched but the only hpfp/vcv tables I’ve seen are pretty random.
from a tuning perspective, you may consider reaching out to carabuser as he is relatively active here and very knowledgeable from the threads I’ve read.
So haven’t been in here in a long time, was here when this awesome forum started. I am a BMW master and BMW diesel master about 20 years with BMW! My job for the past 8 years has been to diagnose cars and that is it!!! I don’t say that to toot my horn I say that to maybe give you some hope that we can get this figured out! I’m no better no smarter than anyone here just more touches to weird problems.. I’ve learned so much from so many of these guys here!
So let’s look at what we have, misfires and backfires. When I hear back fires I immediately think timing, engine timing as we can’t really mess up our spark plug firing order like the old days…
So we can alter cam timing with vanos, think of a ghost cam tune where it chop chop chops like a cammed LS. Vanos units can lock and run very poorly but more often it’s the solenoid that will cause timing like that to act up but you have done them already. N63s would constantly having this problem with vanos units after a repair was done! I have had no starts on N5x engines from fucked vanos solenoids so that’s how far cam timing can swing to a bad spot and they backfire like crazy.
My guess is you have a bad vanos unit that is sticking in and undesirable position. I would also check the hook seals of the cams as they can be broken too. There is a revised seal design that is one pice that dosnt cause further wear and would be a good time to do them.
A video of it as well would help just hearing and seeing it can tell a lot that you might feel are non factors
Good luck and I’ll try and help as much as I can!
So let’s look at what we have, misfires and backfires. When I hear back fires I immediately think timing, engine timing as we can’t really mess up our spark plug firing order like the old days…
So we can alter cam timing with vanos, think of a ghost cam tune where it chop chop chops like a cammed LS. Vanos units can lock and run very poorly but more often it’s the solenoid that will cause timing like that to act up but you have done them already. N63s would constantly having this problem with vanos units after a repair was done! I have had no starts on N5x engines from fucked vanos solenoids so that’s how far cam timing can swing to a bad spot and they backfire like crazy.
My guess is you have a bad vanos unit that is sticking in and undesirable position. I would also check the hook seals of the cams as they can be broken too. There is a revised seal design that is one pice that dosnt cause further wear and would be a good time to do them.
A video of it as well would help just hearing and seeing it can tell a lot that you might feel are non factors
Good luck and I’ll try and help as much as I can!
Thank you for your input. The 98 tune that I am currently running was used for months without an issue before this problem arose so I don't expect it has any connection with this issue and the issue was present when I was running the E30 tune. I am replacing the HPFP just to eliminate it as being a problem and because looking at a log at idle from a couple of years ago, the pressure was 900-850psi at idle and it has now dropped to 700-630psi. On Thursday, I started the car and drove it into the garage. The engine was missing and backfiring and stopped several times. I took a datalog during this which shows the engine running extremely lean and when the STFTs cut in, the AFRs drop back to where they should be. At the end of the log when the engine is idling without misfiring or backfiring, the AFRs, STFTs and LTFTs are excellent. I left the engine idle while I checked the voltage which was 14V. The engine continued to idle without missing and I took another log before turning it off. The second log shows the LTFTs which were acceptable in the first log had gone negative 20% for some reason. This indicates fuel is pouring into the engine. What caused this is the issue. Nothing was touched while the engine was idling. I wish I had kept logging for the entire period to see when the LTFTs changed. These are the logs
datazap.me | Coupes44 | Datalog.120423
datazap.me | Coupes44 | Datalog.120423.1
Thank you for your input. I have also thought that the issue could be timing and that is why I have logged the Vanos readings in the most recent logs in the previous post. I would appreciate seeing a log from another 335i idling showing the vanos readings so I could compare the results with mine. When I logged the vanos readings in the early logs, the vanos exhaust cam actual readings varied in areas with the required readings. I replaced the vanos unit on the exhaust cam which improved this situation.
When you had the valve cover off did you check the hook rings? You have to split the cam carriers… once split you can check the hook rings as well as wear in the cam carriers.
Didn’t watch the video for quality but this is what I’m talking about…
Also a real simple one, the oil filter cap is all in tacked meaning the center section didn’t get throw away by accident
No I didn't remove the camshafts. I just replaced the vanos unit. I know what you are talking about with the hook rings. I replaced a camshaft ledge on my previous engine and replaced the hook seals with the new one piece seals.
Oil cap is OK. I am changing the hpfp at present and looking for any leaks while I have the inlet manifold off.
An update on this issue. It appears that I have solved the issue with my engine. As a final change, I decided to replace the BimmerLife R8 coil system with the standard OEM coils. This immediately resulted in no misfiring/backfiring and the engine has been running fine over the past couple of days. Many will be asking why I didn't do this initially before replacing all of the other components. The reason was that the way the misfiring/backfiring occurred didn't, to me, fit with faulty coils. That is, I could be driving along at 60kph with the engine running fine when, as if you flicked a switch, the engine would begin misfiring/backfiring on all cylinders. I have replaced OEM coils in the past but normally you get a misfire on one cylinder not 6 instantaneously. Over the past couple of weeks, the misfiring/backfiring would be there as soon as I statred the engine and I had to keep the revs up around 2,000rpm or the engine would stop. After a couple of minutes, the misfiring would start to reduce and I could steadily drop the revs to idle with some misfiring which would then go all together. I still couldn't drive the car as there was still some minor misfiring. I am still puzzled as to what caused this behaviour with the R8 coils. The BL harness is only 7months old and tests ok. I have been running the BL R8 system for 5 years fault free. The OEM engine harness which the BL harness connects to can't be the problem as it is operating fine with the standard coils. The other part of the BL harness connects to the power source and earth where you connect the battery charger in the engine bay. Whether there was something in this area going amiss. I am not sure. If anyone has any ideas feel free to let us know. I am just happy that I can now drive the car once again.
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