[ISSA335]

So today out of the blue car started misfiring, not sure if it's because the cold or what, Car is currently on MHD stage 2+ E30 and it was 20-30 degrees today. It doesn't do it in 1st or 2nd but when I'm in 3rd at 100% throttle it starts to break up around 3300rpm( see attached MHD log with torque actual value and rpm values turned on) and you can see the torque starts to build up then just instantly drops off at about 3300 but when I clear the code with my tablet the car runs normal and even pulls hard through 1st and 2nd. Any help diagnosing would be appreciated

https://datazap.me/u/issa335/log-154...data=3-4-22-27

[Emilime75]

How long has it been, and how many miles, since you got tuned? Replaced spark plugs? Coils?

[ISSA335]

Originally Posted by Emilime75

How long has it been, and how many miles, since you got tuned? Replaced spark plugs? Coils?

Been tuned for about 10k miles, NGK 5992's for about 8k miles, and stock coils

[ISSA335]

I'm guessing the temp change is what caused it, the colder the ignition the more resistance, also the engine being under more load in 3rd gear vs 1st and 2nd but we'll see by this weekend when it warms up some, very weird to me that it runs 100% fine after I clear the code

[Sgop335]

Originally Posted by ISSA335

So today out of the blue car started misfiring, not sure if it's because the cold or what, Car is currently on MHD stage 2+ E30 and it was 20-30 degrees today. It doesn't do it in 1st or 2nd but when I'm in 3rd at 100% throttle it starts to break up around 3300rpm( see attached MHD log with torque actual value and rpm values turned on) and you can see the torque starts to build up then just instantly drops off at about 3300 but when I clear the code with my tablet the car runs normal and even pulls hard through 1st and 2nd. Any help diagnosing would be appreciated

https://datazap.me/u/issa335/log-154...data=3-4-22-27

Torque, Plugs and coil lol. Standard ignorance. You are running ridiculously lean at boost. Check your banks in the log and stay away from boost till you fix it!

[ISSA335]

Originally Posted by Sgop335

Torque, Plugs and coil lol. Standard ignorance. You are running ridiculously lean at boost. Check your banks in the log and stay away from boost till you fix it!

Where exactly are you seeing it run "ridiculously" lean at? It stays around 12.1-13 for basically the whole time. When i let off the throttle and was coasting it shoots up to 235 for whatever reason i think because of the aggressive burble it just messes with it but between 12.1-12.6 is where you want to be on a turbo car and in fact, my AFRs are pretty similar to the data log of your car. Just ordered new coils to hopefully help, but your statement doesn't correlate at all, spark plugs and coils aren't going to make the car run lean that would be a fuel related issue, which i will also be doing a stage 2 fuel pump soon

[Sgop335]

Originally Posted by ISSA335

Where exactly are you seeing it run "ridiculously" lean at? It stays around 12.1-13 for basically the whole time. When i let off the throttle and was coasting it shoots up to 235 for whatever reason i think because of the aggressive burble it just messes with it but between 12.1-12.6 is where you want to be on a turbo car and in fact, my AFRs are pretty similar to the data log of your car. Just ordered new coils to hopefully help, but your statement doesn't correlate at all, spark plugs and coils aren't going to make the car run lean that would be a fuel related issue, which i will also be doing a stage 2 fuel pump soon

Guess you didnt catch the sarcasm. Let me spell it out not plugs coils. Its amazing you cant see the obvious below

[ISSA335]

Originally Posted by Sgop335

Guess you didnt catch the sarcasm. Let me spell it out not plugs coils. Its amazing you cant see the obvious below

I'm probably going to switch to my 91 tune for now and my new coils should be here in a few days

[upshift_downshift]

Originally Posted by ISSA335

I'm probably going to switch to my 91 tune for now and my new coils should be here in a few days

Gonna guess your issue is injectors, since your rail pressure looks good. It's definitely a fuel delivery issue. Even your Bank 2 gets above 18 AFR when you got above 4k RPM. Bank 1 looks like it simply wasn't delivering any fuel at some points up there.

Since both banks are lean, I would replace all 6 injectors.

[ISSA335]

Originally Posted by upshift_downshift

Gonna guess your issue is injectors, since your rail pressure looks good. It's definitely a fuel delivery issue. Even your Bank 2 gets above 18 AFR when you got above 4k RPM. Bank 1 looks like it simply wasn't delivering any fuel at some points up there.

Since both banks are lean, I would replace all 6 injectors.

Could I be possible I just put in to much E85 and the fuel pump just can't keep up? Cylinder 1 would be the last one down the fuel rail if I remember right and it doesn't read fuel pressure at each cylinder just at the start of the rail, so could it just be running out of fuel by cylinder 1? ie go mix some more 91 in it? And get a fuel pump and injectors when I can

[upshift_downshift]

Originally Posted by ISSA335

Could I be possible I just put in to much E85 and the fuel pump just can't keep up? Cylinder 1 would be the last one down the fuel rail if I remember right and it doesn't read fuel pressure at each cylinder just at the start of the rail, so could it just be running out of fuel by cylinder 1? ie go mix some more 91 in it? And get a fuel pump and injectors when I can

The pressure sensor is closest to cylinder 6, and the feed line is closest to cyl 1:

http://www.realoem.com/bmw/enUS/show...diagId=13_1182

http://www.realoem.com/bmw/enUS/show...diagId=13_1183

The pressure won't be that much different across cylinders though.

At any rate, with a 200+ AFR you're definitely not getting any fuel into the cylinder at all.

Some back-of-the-envelope math below:
At 14 psi boost you're flowing about 25% more air mass than 8 psi (stock), which means you need ~25% more fuel using pump gas. With E30, you need an additional ~15% by mass relative to gasoline, which brings the total fuel mass flow increase to ~45%.

Source for the E30 fuel mass calc: https://www.concawe.eu/wp-content/up...00668-01-e.pdf

The O2 sensor is actually measuring lambda, not AFR directly, and it just multiplies by 14.5 (I think) to get AFR. So at 18 calculated AFR (the bank 2 max), you are delivering 20% less fuel than you need to in order to get back to stoich.

This means your stock fuel system is maxing out delivering 25% more fuel than what stock boost requires. And that was at 4000 RPM, at 5000 RPM you're already looking at a 25% increase in fuel mass flow. At 6100 RPM, stock boost drops to 7 psi, bringing the total required fuel flow increase to 45% from 8 psi at 4000 RPM.

This means your stock system is definitely capable of providing the necessary fuel flow on E30 fuel at your boost level and that RPM. It just isn't performing in your case, so the injectors are likely problematic. 2300 psi at the rail is very healthy, especially since it is so consistent.

However, you may need to upgrade your fuel system for higher RPM depending on how your boost tapers off, because engine speed adds a heck of a lot of required fuel flow.

[Singh_96]

like the other guy said you're running lean. your afrs are all over the place during the pull. You need new injectors your short term fuel trims are pretty high but your rail pressure and low pressure are both good

[RSL]

Misfires cause the lean AFR readings. The misfire is in bank 2 and starts around 3300rpm. The DME then stops trimming injectors altogether right around the time the torque drops, safety/open loop. Just get out of it when it misfires like that.

Change in VANOS/timing going to the 91 map may be enough to stop misfires, but if you still have E30 in the tank, watch the fuel trims until you fill with more unleaded. Ethanol is more difficult in cold weather, could be partially related.

If I had to guess anything, it would be the NGK plugs everyone thinks are so great, but new coils may help if the current ones are aged. If the coils don't resolve it, gap the plugs down another. 001-.002" or swap them out.

[upshift_downshift]

Originally Posted by RSL

Misfires cause the lean AFR readings. The misfire is in bank 2 and starts around 3300rpm. The DME then stops trimming injectors altogether right around the time the torque drops, safety/open loop. Just get out of it when it misfires like that.

Change in VANOS/timing going to the 91 map may be enough to stop misfires, but if you still have E30 in the tank, watch the fuel trims until you fill with more unleaded. Ethanol is more difficult in cold weather, could be partially related.

If I had to guess anything, it would be the NGK plugs everyone thinks are so great, but new coils may help if the current ones are aged. If the coils don't resolve it, gap the plugs down another. 001-.002" or swap them out.

Now that you mention it, I think you're right! Makes sense with the misfire causing lean readings, since O2 sensors measure oxygen.

[ISSA335]

Originally Posted by RSL

Misfires cause the lean AFR readings. The misfire is in bank 2 and starts around 3300rpm. The DME then stops trimming injectors altogether right around the time the torque drops, safety/open loop. Just get out of it when it misfires like that.

Change in VANOS/timing going to the 91 map may be enough to stop misfires, but if you still have E30 in the tank, watch the fuel trims until you fill with more unleaded. Ethanol is more difficult in cold weather, could be partially related.

If I had to guess anything, it would be the NGK plugs everyone thinks are so great, but new coils may help if the current ones are aged. If the coils don't resolve it, gap the plugs down another. 001-.002" or swap them out.

I'll give it a try thank you guys for the info!

[bundo]

Did you ever solve it