Walked to my car, used the fob as usual to unlock it. Put the key in the ignition, turned the engine over, no start. Engine kept turning and turning, wouldn't fire. I stopped trying, then locked with fob and unlocked with fob, then it started up just fine. WTF!!!

2500 miles, 3 weeks old. First time this has occurred. My guess is the engine immobilizer kicked in, but why?

Don't laugh, but did you by any chance have the keys to another late-model Nissan and or Inifiniti with you (in your pocket) or inside the car. It happens quite often, where the ECU picks up another key and "thinks" its trying to be started by the wrong key. If you had no keys near you, then it picked up some interferance or just had a "electronic fart". Its not common but I guess it could happen.

This happened to me at a gas station once after getting filled up. I took the key out, waited a second or two, put it back in, and it started right back up. Very strange.

My wife has a 2003 3.5SE Altima. Her key has been in my center console for a few days. Does her car have that chip in the key? LOL, that can't be it. People who have an infiniti and/or nissan, chances are they have another in the garage, and multiple keys on the same key ring. Interesting thought tho.

We have 3 Nissans in the house.. Needless to say it gets confusing lol

Sometimes when you get int he car, put the key in the ingintion and turn it right away it may not recognize the chip. I have had this happen in my other car before. i guess we are just too quick for the sensor some times.

the last time the car was on, before the failure to start, did you run the car for a very short time? Like perhaps to move it from one parking spot to another? Or drive it for less than 5 mins?

did you depress in the clutch fully?

junky gas, happened to me twice.

Wow...you must drive A LOT!

Apparantly the ECU mixing up keys is for real. I ran into this with my new M.
They told me to keep other (chipped) keys away from the dash or center console.
C.

This happened to me once. I was at my brother's house, and the car wouldn't start for a long time (several minutes). I went inside and waited a few minutes. I came back out and it started right up.

a VQ that isnt broken in yet often has hard start issues when the engine is shut down before its fully warmed. If its shut off in open-loop, it will be very rich and nearly fuel fouled when you return. It decreases over time, but it still happens.

the other key would have to be right next to the ignition for it to pick anything up. thats what makes doing a remote start kinda difficult on cars with the immobilzer's. its not like you can pick up a signal anywhere in the area of the ignition, you have to have it up against the key cylinder.

I have 2 nissan keys on my key chain (G and pathfinder), neither car ever cares. Thats in over 2 years with the G.