Cylinders 4 & 6 are both misfiring for me. I changed coils, plugs, injectors, o2 sens., used fuel injector cleaner and nothing. The car shakes and I smell unburned fuel. Before it started misfiring I took a while to replace the bank 2 oxygen sensors. Could the misfire be an effect of that bad o2 sensors? I made sure I have no intake leaks so that’s not where it’s coming from. Took it to the dealer for service the only two options they gave me were to replace the coils with brand new ones. I had replaced them with an old used pair. But if that doesnt work they’ll have to upgrade the ecu which I believe will only mask the problem. Does anyone have any suggestions or recommendations for me? It would be greatly appreciated

 

Are you certain you don't have the the connectors going to the coils for cylinders 4 and 6 swapped? I think it's more commonly seen on bank 1 but might be worth checking.

 

I accidentally did this to my car. Ended up frying my cat before I could figure it out.

 

First, as suggested, make sure you didn't swap the coil pack harnesses, 2006 I think they started using brady labels on the wire so it should literally have a little number 2, 4, 6 wrapped around the individual coil packs. Might have just been the rev-up motor they did that on though.

If you suspect a coil pack then swap it with one on bank1, just make sure to identify the coil pack with a sharpie so you know which one/s are potentially bad. If the code changes to a misfire on the cylinder you swapped it to then you know it's a bad coil pack. I strongly recommend only using the factory Hitachi coil packs or OEM Nissan ones (Hitachi was the OEM manufacturer for the DE engine).

Hitachi part number IGC0007

You should inspect your existing ones though, look up into the rubber spark plug well tube boot up and see if the contact spring is all corroded or damaged. Also make sure there's no oil in the spark plug well tube.