My CEL came on a couple days ago. Next start it did not come back on. Couple of trips later it came on & engine was running rough & misfiring. Turned engine off & restarted and it was fine. CEL stayed on so I took it into the dealer.

The dealer said the codes were 0649 and 0637, misfires on cylinders #4 & #6.

We moved the coil packs to other cylinders to see if the misfire follows the coils.

Has anyone seen this problem before? Is this the start of the sprocket on the balance shaft going bad?

Thanks!