[serrated]

First off, it's a '14 rwd zf8 m235i.

Second, the only mod is the stage 1 hex tune.

It runs great, but this week it felt like the transmission wasn't upshifting despite the fact that my foot was in the floorboard and the transmission was in D or S.

After testing some more I think the engine is actually misfiring or something about 500-1000 rpm's before redline, which sounds/feels like it's cutting spark or timing almost, so the tranny never upshifts because it slows and takes longer to get to the shift point. This is just speculation because I still have no idea what it could be.

I just went to dyno the car a few days ago. The guy mentioend something about spark plugs maybe and something about higher rpm's. I don't remember exactly what he said but this came to mind today when I had the car do this again.

So let's assume plugs ARE the issue. Car has 35k miles. Do you think it needs new plugs? Perhaps colder plugs or maybe they aren't gapped properly? Or do you think a coil pack is going out? Maybe plugs are fouled?

Weird thing is, if it really is misfiring I would've expected a check engine light. (but there is none)

Any help is appreciated. I'll try to get video of it doing this tomorrow

[Zwei]

If there is no CEL the engine isn't misfiring.

[Unicorn123]

Would it make sense to remove the hex tune module and return the car to the OEM ECU to confirm that the issue exists? If the issue is resolved, then you can narrow it down to the tune and tune coding, I would think.

[mike@x-ph.com]

Misfires dont always throw a code, they will once its really bad.
That being said, you need to datalog before paying money and changing parts

[serrated]

Originally Posted by mike@x-ph.com

Misfires dont always throw a code, they will once its really bad.
That being said, you need to datalog before paying money and changing parts

I'm used to the cobb accessport world where I can use the accessport to datalog... what do you recommend using for datalogging for my bimmer?

[MarcoZandrini]

First, check the plugs in the engine for color. The insulator should be a light tan/brown. A plug that’s too hot will show up as having white deposits on the insulator and/or damaged electrodes. Plugs are gapped by the manufacturer. The plug and the its gap are specified by BMW, based on recommendations from the spark plug manufacturer. That said, I highly recommend that you always replace spark plugs with what BMW put in the engine. Replacing factory plugs with another brand (i.e., Bosch in place of NGK) is not a good idea.