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Old 01-07-2008, 05:30 PM   #11
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Originally Posted by bill buttermore
You can test the knock sensors with a scan tool by tapping on the block and watching for the response of the knock counter. A scan tool will also tell you if timing is being retarded, although, if it were, you would probably be able to feel it.

the knock sensors are designed to listen for a specific frequency. they are only supposed to react to the frequency of detonation. so, will the test of knocking the engine, work, if its a different frequency than actual detonation. ive never tried it so, im curious.
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Old 01-08-2008, 01:18 AM   #12
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will the test of knocking the engine, work, if its a different frequency than actual detonation. ive never tried it so, im curious.
IIRC, that is one of the tests to determine whether or not the knock sensors are working. I'll check my FSM to make sure. Yeah, I checked my '95 FSM, and that is part of the procedure to check to see if they are working. Presuming there have been no significant changes in the sensors since then (?) that should still work.

I know my '95 when I bought it had some valve train noise that caused the knock sensors to retard the timing as much as 17 degrees. This is called false knock and is caused by the sensor picking up sounds that it thinks are detonation but are not. Recalling the sound of spark knock, I am guessing that the frequency varies from high to low over several thousand hertz. To catch all of the possible frequencies of detonation, I would think the sensor frequency range would need to be wide enough that it could not avoid picking up other engine knocking sounds.
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