PicoScope 7 Automotive
Available for Windows, Mac, and Linux, the next evolution of our diagnostic scope software is now available.
BMW N63T Misfire/Vibration
BMW N63T Misfire/Vibration
Hey guys,
I'm working on a vehicle that has a light-under load misfire (or at least it feels that way..). There are no faults and I'm able to get this thing to "misfire" by crusing around 35-45mph and lightly tipping-in on the throttle. It feels like a fishbite type misfire. I'm new to the picoscope, but have used scopes in the past for many years so setup isn't a big deal necessarily for me... I decided to scope the crank signal and use a math channel for frequency so I could see the crank speed and drive the car with a trigger on cyl#4 (not sure why I chose that but I'm picking up primary coil signal @ the DME (engine computer bank 1). According to service data, firing order is 1 5 4 8 6 3 7 2. Based off the image, it would appear cylinder #6 is having an issue. I don't have a lot of exposure to this kind of in-depth diagnosis, but what I can tell you is I've replaced all the coils/plugs/injectors and even did the plug/injector on cyl #6 again AND moved the coil to another cylinder. My next move is to check the activation of injector and coil for that cylinder during the misfire event. However I was curious as to whether readings of this nature could be indicative of anything OTHER than a misfire i.e., torque converter/slipping transmission/normal operating strategy etc..? I would find it unlikely to be anything other than a misfire but I've been going round and round with this car and now I'm wondering if I'm feeling something and seeing something else.
Any feedback is appreciated. Thanks!
I'm working on a vehicle that has a light-under load misfire (or at least it feels that way..). There are no faults and I'm able to get this thing to "misfire" by crusing around 35-45mph and lightly tipping-in on the throttle. It feels like a fishbite type misfire. I'm new to the picoscope, but have used scopes in the past for many years so setup isn't a big deal necessarily for me... I decided to scope the crank signal and use a math channel for frequency so I could see the crank speed and drive the car with a trigger on cyl#4 (not sure why I chose that but I'm picking up primary coil signal @ the DME (engine computer bank 1). According to service data, firing order is 1 5 4 8 6 3 7 2. Based off the image, it would appear cylinder #6 is having an issue. I don't have a lot of exposure to this kind of in-depth diagnosis, but what I can tell you is I've replaced all the coils/plugs/injectors and even did the plug/injector on cyl #6 again AND moved the coil to another cylinder. My next move is to check the activation of injector and coil for that cylinder during the misfire event. However I was curious as to whether readings of this nature could be indicative of anything OTHER than a misfire i.e., torque converter/slipping transmission/normal operating strategy etc..? I would find it unlikely to be anything other than a misfire but I've been going round and round with this car and now I'm wondering if I'm feeling something and seeing something else.
Any feedback is appreciated. Thanks!
- Attachments
-
Re: BMW N63T Misfire/Vibration
Hello,
For this issue I will record the secondary voltage ignition with COP probe to catch injection malfunction like in the attached file(please look at cyl 4 burning time compared to the other
/ at the 4th injector(with lower spray cone,lower injected quantity )compared to
the first injector ) or a low compression.
Best regards
For this issue I will record the secondary voltage ignition with COP probe to catch injection malfunction like in the attached file(please look at cyl 4 burning time compared to the other
the first injector ) or a low compression.
Best regards
Last edited by victor2k on Sun Oct 03, 2021 12:23 pm, edited 3 times in total.
-
Steve Smith
- Pico Staff Member
- Posts: 1594
- Joined: Sun Aug 25, 2013 7:22 am
Re: BMW N63T Misfire/Vibration
Hello and thank you for the posts
Based on your image I would agree there is minimal crank acceleration from cylinder 6 after the ignition event.
It would be advisable now to physically measure current flow via cylinder 6 injector (or indeed all 8 if you can get a current clamp around the supply fuse)
I am assuming you have 4 channels to work with? If so……….
I would also include Cylinder 1 and Cylinder 6 ignition events too (Use 1 for sync and 6 to confirm the presence of a spark)
I know this will cost you 2 x channels for confirmation of ignition but if we are losing cylinder 6 ignition, we still have cylinder 1 for sync purposes
Next round of testing; I would either choose MAF or MAP, my thoughts here turn to a mechanical issue given you have replaced ignition and injection components for cylinder 6
We should have uniformity in both these signal for 8, evenly contributing cylinders. Say for example during the misfire we have a clear disruption to the intake pull of cylinder 6, this could lead us off in a whole new direction.
Regarding slip in a torque convertor, in this scenario we are likely to see the engine speed momentarily “flare” (increase in speed) and not produce the sequential reduction in crank speed (every 6 cylinder firing event) we see in your image above
I hope this helps, take care…..Steve
Based on your image I would agree there is minimal crank acceleration from cylinder 6 after the ignition event.
It would be advisable now to physically measure current flow via cylinder 6 injector (or indeed all 8 if you can get a current clamp around the supply fuse)
I am assuming you have 4 channels to work with? If so……….
I would also include Cylinder 1 and Cylinder 6 ignition events too (Use 1 for sync and 6 to confirm the presence of a spark)
I know this will cost you 2 x channels for confirmation of ignition but if we are losing cylinder 6 ignition, we still have cylinder 1 for sync purposes
Next round of testing; I would either choose MAF or MAP, my thoughts here turn to a mechanical issue given you have replaced ignition and injection components for cylinder 6
We should have uniformity in both these signal for 8, evenly contributing cylinders. Say for example during the misfire we have a clear disruption to the intake pull of cylinder 6, this could lead us off in a whole new direction.
Regarding slip in a torque convertor, in this scenario we are likely to see the engine speed momentarily “flare” (increase in speed) and not produce the sequential reduction in crank speed (every 6 cylinder firing event) we see in your image above
I hope this helps, take care…..Steve