Knock sensor code + symptoms

[skizsystem]

my KA has been running like major crap lately and i just check my diagnostic code right now and its throwing knock sensor code. now ive had problems with knock sensors on other cars before but none of em showed any real symptoms, sometimes i couldnt even tell the difference.
here are the symptoms i have now
-Black smoke
-wont hold idle at times
-boggy/hesitant at time
-really bad mpg

my question is will a bad knock sensor really mess up performance that much? any help is greatly appreciated

[japslapsilvia]

If the knock sensor is damaged or has cracks it will usually put ecu in safe mode an it will pull timing ....will make it seem like a fuel cut ....

[KoukiDrifter240]

i heard knock senson is bad it won't start

[nismolvr]

If the knock sensor is damaged or has cracks it will usually put ecu in safe mode an it will pull timing ....will make it seem like a fuel cut ....
exactomundo! disconnect ksensor and check for 5 volt reference from ECU , if no voltage .you just isolated the problem , and its a power issue to knock sensor (sensor still good).you have an open circuit in harness.
Knock sensor is a resistor and when its connected in series it drops the reference Voltage to about 2.5 volts wich the ecu monitors. Whenever the k sensor detects pinging/knocking ,voltage fluctuates away from the steady 2.5 , computer then retards timing to protect engine. when engine stops knocking voltage goes back to steady 2.5 and No code is set.When steady 5 volt is seen computer sets Code ,and fail safe. problem is usually a bad K sensor. Hope this helps.