I have an 02 Altima 2.5 that I just purchased a few weeks ago. Seemed that the only problem it had was a "noisy idler pulley" which of course turned out to be the clutch assy in the alternator. Got that fixed and drove for a week or so and at about 70 miles into a 100 mile one-way trip, I get off interstate to see my oil pressure light come on, mashed the gas and it goes off so I pull in the gas station. I had been hearing a noise since the alternator fix that I wasn't sure what it was but assumed it wasn't new but just couldn't hear it before because of the alternator/pulley horrible noise....anyway, oil pressure light had come on day before, checked the oil and it didn't register, put 5W-30 Pennzoil in and it registered full and still does. So, I sit at the gas station for a couple hours waiting on someone to follow me home, crank the car and no light, get back on interstate go about 20 miles to get off to get gas, take foot off pedal and light comes on, mash the pedal light goes off. Drive home using gas and brake pedal simultaneously and not coming to complete stops in order to keep the light from coming on. Start it up the next day to go to my mechanic and no light until stopping at stop sign about 12 miles later. He's unsure as to what it is...says its not the sending unit and that it must be in the motor somewhere and said something about the bearings. I only assume he actually checked the pressure.....I also have a check engine light that he says codes to be the crankshaft sensor....HELP, PLEASE!!!