Sensor ring adaptation is reset to original coding by a scan tool, but actual adaptation is done on the road or dyno. It sort of takes a tool to know that one is in the load/rpm block to adapt the first block. After that the rest are left to adapt themselves. Untill some level of adaptation is achieved the controller won't recognize a misfire. Not that it couldn't, it just needs that level of adaptation for the software to allow it.

Full load misfires due to cat restrictions are common on that motor. I would probably replace the plugs as stated for the time reasons stated and then not do anything else till another code appears. I would probably also move the coil packs to an adjacent cyl and note that at the same time. If the problem has anything to do with cats or overall mixture, the misfire will likely appear on a different cylinder.

If a repeat misfire comes from the cylinder that now has the pack that was on #3 previously then I would replace the wires on that cyl and repeat the testing.

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Steve Brotherton
Continental Imports
Gainesville FL
Bosch Master, ASE Master, L1
33 years MB technician