effect of a bad knock sensor?

[nekoabandoned]

i know im throwing a knock cel , im just wondering if that was all that was causing all my problems. i just came from building hondas for 6 years to my first nissan so please bare with me. i know when honda's throw a knock code they retard the timing and rush over 3 bars of gas through the motor, are nissans the same?so basicly im asking for a list of symptoms for a broken knock sensor.

btw i know how to fix it , i just only have so many hours in the day to do stuff because of work. so id like to know if this is the only problem.

thanks for any help , nick
Modified by nekoabandoned at 12:30 AM 10/8/2008

[nekoabandoned]

bump for some answers

[romerider153]

is it an sr ka what

[modulation]

Nissans (ka/sr) have knock maps.Both a knock fuel map and a knock spark map.These maps will pull timing and make the car run richer.

Most aftermarket engine management or tunes at least partial disable the knock sensor though..

[grecco28]

the ecu retards timming i think use a diferent values for that condition...in fail safe mode...

[MxExUx]

A broken knock sensor is not going to falsely indicate knocking in the motor. It is simply not going to detect knocking when it actually is occurring. What may be happening is that circuit could be getting interference from somewhere either electrically in the wiring or through noise physically being transmitted.

[modulation]

I big to differ.From my understanding the knock sensor is a piezoelectric disc.The ECU looks not only at Voltage but at the resistance of the circuit. If the knock sensor is broken in such a way, it is possible for the ECU to see a lower resistance/higher voltage then normal and think it's the knock sensor going off when it's not.

[MxExUx]

You are right that it is a piezoelectric crystal. This crystal creates voltage when it gets even the slightest of amount pressure applied to it making it ideal for detecting knocks in the motor. The ECU basically only detects knocks when it sees voltage coming from this sensor. So I really don't see how if this sensor is broken it can be sending voltage to the ECU making it think there is detonation occurring.

[MxExUx]

If you want to test my theory just unplug the knock sensor (which many people do) and see if you still have this problem. I really don't recommend doing this for a long time though because your motor could actually be detonating and the ECU won't know to take preventive measures. If you are still reading knock with the sensor unplugged then you most likely have some sort of electrical interference issue.