My 2004 fx35 has 154,000 mi. #5 is misfiring; the plugs & coils have never been replaced. Should I replace plugs and coils for all 6 or just the plugs?

If you've owned the vehicle since new & are certain the plugs haven't been changed, then it wouldn't hurt to do.

Typically I don't replace a coilpack unless it has failed. Also, what I do is move that coilpack to a different cylinder to see if the code moves too, and that isolates the coilpack as the issue.

Good luck.

I bought the Infiniti used when it had about 120,000mi. on it. I will try your suggestion, thank you.

When replacing the plugs on my Infiniti fx35 the #6 plug had oil on the top of the plug and inside the coil; what do I need to do to fix this problem?

I think the consensus for most plastic/ composite valve covers is that you just replace the entire VC. In the older metal ones you could replace the tube seals. Maybe some RTV around the spark plug tube or some other creative way of getting an O-Ring there will buy you some time...

I would defer to the G35 crowd on this one.

Tks for your help.