Knock Sensor Question

Hello,
I am new to this site and would just like to know more about the knock sensor. To make a long story short, my 96 Maxima has been bogging and dying when I come to a stop. It has been at my mechanic for 4 weeks now, nothing short of a mystery to them. At first I thought it was the fuel, but that came back as testing fine. They replaced the computer system with a refurbished one hoping that that would solve the problem and it hasn't. They have replaced the fuel sensor, and the cam sensor. Prior to replacing the computer system, Nissan diagnosed my car as having a bad knock sensor and cam (after I had gotten the cam replaced-go figure). Would the knock sensor cause these problems? My mechanic says no, and I honestly don't doubt him, but I have to get ideas from other people. What exactly does the knock sensor do? And if it is bad what kind of problems would that cause? If ANYONE has a solution to my dilema, PLEASE let me know.
For the record my car has 122,000 miles on her.
Thank you,
Kathy

This may shed some light on what a Knock sensor does.
http://www.motorvate.ca/auto/maxima/knock/knock_sensor.htm

Change your front o2 sensor. The one B4 the cat.

You may also have a MAF problem. (Mass Air Flow Sensor)

My theory on the knock sensor is that something else in your engine causes the ping/knock. Fix that and the knock sensor will stop retarding your timing. Your power will come back!