Knock Sensor ??? again

[kathyb820]

First I would like to thank Ravq for replying to my post. I was sooo excited to finally see someone reply. I read the web link...thanks!!!
But with my first post...I just want to know if the knock sensor is bad would that cause the engine to bog and die out? I really do not understand the terms given for cars.
What exactly does this mean? (see below)

"When it hears engine knock it sends a signal to the ECU. (Engine Control Unit) The ECU normally will delay (or retard) the ignition advance. This stops the engine knock, and decreases engine power."

To me this sounds like the problem I having with my car. My mechanic says that the knock sensor would not cause these problems. Thats why I am so confused. Since Nissan came back stating that it was bad, my mechanic has not replaced it, thinking that there is another problem (somewhere) that is causing all this. Should I tell him to replace it anyways? What is engine knock? "Decreases engine power"...bogs out and dies? HELP!!!! AAAARRRGGGHHHH!!!!!! I miss my car!!!

[Ravq]

I agree with NJMAXSELTD in your other thread. The knock sensor wouldn't cause these symptoms rather something else would cause the knock and thus causing your KS to retard your timing. NJMAXSELTD also brought up that you may also have a bad MAFS (Mass Air Flow Sensor) which cause your car's idle to run eratic and cause it to stall out. This is fairly simple to test.

It is very easy to test the MAFS all you need is a voltmeter or multimeter to check the voltage while engine is off and key is at "ON" position. You'll need to backprobe terminal one (left most connector) on the plug. It should be less than 1.0 volt. With the engine idling at operating temp is should be 1.0-1.7 volts. With the engine running at ~2,500rpm it should be 1.5-2.1 volts. You should observe a linear voltage rise in response to increses in engine rpm up to about 4k. If voltage is within spec you can also check the power and ground circuits.


Also NJMAXSELTD recommends you change your O2 sensor because the MIL codes for the O2 and KS occuring together seem to run hand in hand.

[NJMAXSELTD]

Nissan told you the KS was bad? I don't remember seeing that comment in the 1st thread.

There are tests that can be performed on the KS to see if it truly is bad. The Haynes manual has some specs on it. Might want to have the KS actually tested first too.

It could very well be a bad KS as well, so lets not rule that out just yet.


Hope I didn't take you off track in my last post.

[Ravq]

Well if Nissan told her is the KS was bad maybe they already tested it.