So my car threw these codes at me today: P0302 and P1399. I already know that the codes are misfire codes, but I was trying to dig a little more and see what insight others may have on this issue.

The car runs smooth, starts up like normal, nothing out of the ordinary until you give it full throttle. The car will get up to about 5800-6000 rpm and that's when it seems to misfire and lose some of it's acceleration. Also, the CEL didn't come on until I hit about 5800, so it wasn't on when I started the vehicle, but stayed on after that.

So basically what I'm getting at, what would cause it to misfire at higher rpms, but not when just driving around normally?

 

Last full tune up?
Valve adjustment?

 

Plugs are new, everything else I'm unsure of when it was done last. The wires look alright and the distributor cap itself looks newer than the rest of the bay. I'll swap out the wires and distributor rotor this weekend and see if that fixes it.

 

Somehow the check engine light went off on it's own. I didn't fix anything yet or reset the ecu. Still misfires around 6k.

 

Replaced the plug wires with NGKs and installed a new fuel filter that's been sitting in my trunk for that past three weeks and the car runs fine now. Revs more freely, no misfiring in the high revs anymore.