My '03 G35 coupe tries to crank but won't start. This is a new issue. A few days ago most of my gauges quit one after the other, the car began shifting early and hard, the slip and vdc off lights came on, the gear indicator became intermittent, the at check light would come on and the lights on my console would flicker out. Seemed like my car had a poltergeist. The next morning, the symptoms disappeared. The next few days, my car would attempt to crank but not start. I would jiggle the keys and then it would start. After two days of those symptoms, my car would either crank and not start (& I'm talking a very small and short crank), or it was a no crank, no start (that varied). A friend suggests my ignition switch is experiencing grounding issues, and my father proposes the ECU may be going out. Any thoughts?

 

From your description, yes I think that is where I would start. There is about a bazillion wires that are switched by the key and if the switch gets out of alignment, it can cause all kinds of trouble.
Did you or the previous owner have a large ring of heavy keys hanging from it? Worst thing you can do.

 

My brother recently mentioned the same about having a lot of keys on the keyring. I have a decent amount on mine; however, I'm not sure about the previous owners. Additionally, the plastic around the chip is cracked on the key. Not sure if that could cause problems? The ignition switch is pretty loose where the key goes. I've ordered a new switch and key. Thank you so much for the insight!

 

My brother recently mentioned the same about having a lot of keys on the keyring. I have a decent amount on mine; however, I'm not sure about the previous owners. Additionally, the plastic around the chip is cracked on the key. Not sure if that could cause problems? The ignition switch is pretty loose where the key goes. I've ordered a new switch and key. Thank you so much for the insight!

 

Be sure it's the ENTIRE switch, not just the tumblers and key.

 

Thank you. I ordered it off eBay. Here's a photo. Does it look like everything I need?