I was driving my car to school, and one day while driving back, my Nissan Xterra's 2001 engine just turned off. I had just exited the freeway and as soon as I got to a red light, the car turned off. I did not have any prior problems so I wanted to know what the problem is. There were no problems previous to this happened. The mechanic came to my house and took a glance at it and said that the valves are bent, and since its an interference motor he said it needs to be replaced. He took a look at the ignition rotor and said that there was no sparks coming out from the wires and thats why the motor would not turn on. is there any chance that the timing belt just went bad? or the spark plugs are bad? or is it what the mechanic told me and i need to replace the engine? I did buy a new battery for the car but other than that I have not done anything else. THanks for the help guys!

maybe this will help? I'm not sure...
http://www.clubxterra.org/forums/showthread.php?t=23546

Take the cap off of the distributor and see if the rotor inside turns when someone just BUMPS the key (real quick turn to start). If not, the t-belt most likely took a dump.

If it does turn, the distributor its self may have just taken a dump.

Now if the t-belt did go, there's a chance for bent valves. The PT Cruise also has an interference motor, and when the t-belt broke, we just went ahead and changed it on the off chance there was no other damage. It's been running "good" since.

agreed there is a chance it could still be good. What was the mileage again? A new engine is a big jump to make from not starting... Any weird noises when you try to start it? Any check engine lights?

your motor is fine, your mech is shit, any mech that goes with the hardest most expensive troubleshoot first is garbage. it sounds electrical lets start there.

Yeah, the mechanic took the cap off the distributor and the rotor inside did not turn when the I bumped the key. After doing that, he just said that it has to be the motor and that the valves probably bent because its and interference motor. I have my doubts that it that! I have always taken good maintenance of the vehicle. And the mileage is 170000. It was my mom’s car before she handed it down to me last year. And no, there is no weird noises when I try to start it, it seems like its going to turn on fine, but it just needs that last push to do so. The check engine light is on, but im not too sure if it was ever reset after it reached the 100000 point.

If the rotor didn't turn, then most likely the timing belt is shot.

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I have my doubts that it that! I have always taken good maintenance of the vehicle. And the mileage is 170000. It was my mom’s car before she handed it down to me last year. And no, there is no weird noises when I try to start it, it seems like its going to turn on fine, but it just needs that last push to do so.

What you explained happened to me. You have 170,000 miles and I bet the timing belt hasn't been changed.