To prevent the replacement of good components, be aware that the following non-EEC areas may be at fault:

• Fuel (quality)
• Fuel (octane)
• Basic engine
• Spark timing

The knock sensor is used to detect engine detonation (spark knock). As a result, a voltage sent to the PCM will retard spark timing. The KS is a piezoelectric accelerometer with the sensor designed to resonate at approximately the same frequency as the engine knock frequency. The KS uses the resonant frequency to mechanically amplify the vibrations. This method allows relatively large signals to be achieved without electrical amplification and with small package size.

The sensor has a thin circular piezoelectric ceramic disk which is bonded to a metal diaphragm. Electrical connections are made through a two pin integral connector.

Vehicle	Knock Resonace Frequency	Part Number
5.0L F-Series / Bronco / Econoline	5.45K	E3AF-AA
3.0L/3.2L Taurus SHO	6.0K	E5TF-AA
4.9L F-Series / Bronco / Econoline	9.5K	E9TF-AA
3.8L Supercharged Thunderbird	5.7K	E9SF-BA
4.6L 4V Mark VIII	6.15K	F3LF-AA

Article & images courtesy of fordfuelinjection.com.