Misfire P0300 above 2000 RPM


New member
I'm getting a consisten misfire above 2000 RPM on four cylinders. Looks like 1 5 6 8, worst offender is number 6. It doesn't misfire under 2k, consistently reproducible above.

- I've change the spark plugs for 8 with no change
- I've swapped the coil on 7 and 8 with no change

So fairly certain not a ignition issue. Fuel pressure is a constant good PSI, in range. Doubt vacuum leak cause it gets worse at higher RPM and not surging with the starter fluid test at idle. Also doesn't seem to be one bank or the other, distributed across both banks. Haven't checked any injector related yet but seems unlikely due to only above 2K RPM.

I was thinking I might need to do a Crankshaft Error Relearn (CASE relearn). Anyone done this in these conditions?

I've attached screenshots of freeze frame data from P0300 code as well as misfire counts and fuel trims at low and high RPM (current misfire count on left, history misfire on right)