knock sensor should be retarding timing until the car is turned off - i.e. short term safety boost. So the next time you hear it. go home and stop the car but don't turn it off. Then while it's idling check your timing with a timing light. Then turn the car off for 30 seconds or so to erase the short term safety boost, restart the car and check the timing again and see if it is the same as before. If the second time you check the timing it's higher, then you've been detonating