Odd CEL after big bump
 

I've got a 2004 MT with 87k miles on the original engine and maybe 30k miles on the current coils/plugs/wires (over 6 years since I got another DD vehicle 5 years ago). Just had the clutch/flywheel replaced about a month ago and have been running the RB intake for at least the last 8-9 years.

Over the weekend, I hit a decent bump on a freeway ramp and may have had all four wheels off the ground momentarily (not sure if it was all at once or in pairs, or if it even really got airborne at all for sure) which led to the CEL coming on. Code reader showed P0302 (misfire), but I didn't hear any knocking or notice any power loss for the rest of the way home. I haven't had any prior history of these kind of codes and haven't driven the car again since clearing the computer (got the taillights off to finally seal them up properly at the moment, probably won't be ready to roll again till next weekend).

Anyone ever heard of something like this?

I wouldn't worry about it unless it comes back. It's plausible that the ECU could register that kind of shock as a misfire.

I didn't after hitting a bump, but I had one after a hard braking and downshift once when I lost traction.

The P0300, P0301, and P0302 CELs are triggered by an unexpected change in eccentric shaft position change (actually a number of events, but one large event could trigger them). That means the eccentric shaft speed not slowing down, speeding up, or staying constant EXACTLY when the ECU expects it to will constitute a misfire event.

The ESS trigger wheel is notched in such a way that the pulses the ESS "sees" contains all of the information about the current position/combustion cycle of each face of each rotor. An unexpected change in the eccentric shaft angle delta at a certain point in the rotation of the shaft is enough to tell the PCM a) that an event has occurred, b) which combustion chamber/rotor it occurred in, and c) which combustion cycle and rotor face it occurred on (even though it's not reported).

Technically a hard enough bump could have done it, especially if you look at it from the perspective that the ESS might have been shaken, rather than the trigger wheel. If it ever comes back you should look into the normal misfire causes.

Thanks guys.

I had kind of suspected that if my back wheels came off the ground under power, the brief extreme increase in RPM (I think the traction control light gave about a half-blink as well) was the culprit in triggering the CEL, I was more surprised to see the code for a misfire when I got home and plugged in the scanner.

Following any misfire code you should always reset the ESS profile (20 brake stomp procedure). If the code keeps coming back then you gave to investigate the possible cause.