I brought my 2003 g35 coupe in for an engine swap and the mechanic didn't finish the job.

2003 Infiniti g35 coupe with an 2004 engine... They said the engine ran like crap. They also said the starter didn't work with newer engine.

This is a video of what happens...

So do I need a new starter and ECU reflash?

 

Is your car 6mt? if so, then if the dash light goes off while you hold the key on "START" then goes back on when you realease the key to "ON" ==> it seem like your clutch pedal sensor doesn't works...

Otherwise I don't know sorry.