Okay I have a 2003 350z Toruing with 63,000 miles and recently my check engine light came on so I took it too a Nissan Dealer they told me it was misfiring in the 2nd cylinder. So they switched the coil packs to see if that was the problem but it wasn't it kept doing it. So then they thought I should pay them $400 to do spark plug and fuel injection Carbon Clean out. Well I only run the best fuel for my car and I beat on it plenty so there shouldn't be any Carbon jammed up. I took out the spark plugs and replaced them, they looked fine and still I have the same problem. Has this happened to anyone else's Z and what is the problem? I appreicate the help.

 

Never had it on the Z, but my old Saturn was running hot and having occasional misfires and it turned out to be the head gasket. Only found out because I was replacing it anyways and it just happened to fix my misfire problem.

 

Dealers love these clean outs: radiator clean out, fuel system clean out. Usually its just a $5 bottle of magic juice that does little or nothing.

I assume that the problem is more complicated than carbon build up.

 

Dirty injector would be my guess. Not all that tough to swap two of them to see if the problem follows the injector but you will have to remove the upper & lower plenum and then reassemble. Don't pay the dealer to do what davidv mentioned above!