Nissan Repair: missfire cylinder 5, water under the bridge, compression check

Question
hi i have a 350z and a got missfire code on cylinder 5 ,they said it was the ring that broke on the piston so we put a new engine in the car wen whe stated new engine same probleme miss fire code on cylender 5 again,my car runs on only on 5 cylinders cause the cylinder 5 dosnt work ,my guest it a electronic probleme on cylinder 5 because even whit new motor still same probleme on cylinder 5

Answer
Nic,

Either the fuel injector is not firing.  I have a 2003 350Z and have had this problem on three different cylinders.  Another issue would be the coil not firing.  And, last would be the computer not allowing the coil for number 5 to fire.  I would check in this order.  I am sure there has been a compression check on number5?  That would have verified a broken ring or a burnt valve.  This is water under the bridge since you have replaced the engine.