I had a 02 navara up until recently, to be honest it was a good motor all the time i had it, but there was a fault with it. Every now and again, normally if you started it and stopped it quickly, the engine would rev at about 1500 - 2000 rpm. To reset, you had to start it up, not touch the throttle and leave it ticking over for about 5 minutes, it would then reset itself.
Obviously a manufacturing fault, but nissan wouldnt fix it.