Help!! '04 350z with about 78,000 miles on it. Occasionally it won't start and it sounds like a drill. I think it's the starter or spark plugs?

 

Not the spark plugs.

Check your battery - stop by an auto parts store and have them check it, if you don't know how. Make sure all the connections at the battery are clean and tight. Check all the connections on the starter motor and solenoid.

If all the above checks out, pull the starter. Look at the teeth on the pinion gear and ring gear (flywheel). If they all look good, buy a replacement starter.

 

^^^ This.

Sounds like classic non-engagement between pinion and flywheel teeth where the pinion won't deploy or all the teeth are missing.

You can always test the starter once it's out of the car using the old jumper cable method. Just watch out for runaway starter!! Heh heh.... my hot rod days will never go away, will they?

 

it amazes me how little people know about cars now days.....

 

I'd say the starter or flywheel is missing a few chunks. like mentioned.. pull the stater and inspect. have a buddy bar the engine over with a socket and inspect the flywheel.