V8 Quattro V8-3562cc 3.6L DOHC (PT) (1990)
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Knock Sensor: Description and Operation
DESCRIPTION
Two knock sensors are used to signal the Engine Control Module (ECM) when a sudden severe detonation (knock) occurs in the engine. One
sensor is fastened to the engine block, in the valley beneath the intake manifold. The other is bolted to the left side of the engine block, beneath the
cylinder head. When a knock is sensed, the ECM retards the ignition timing, in steps, until the knock ceases.
Ignition Maps And Knock Sensor Control
The ECM has two ignition "maps" programmed into its memory. One for premium fuel and one for lower octane fuels. The premium fuel ignition
map is normally the one referenced by the ECM. If knocking cannot be eliminated by retarding the ignition timing the maximum number of
degrees from the mapped point on the premium ignition map (12 degrees), the ECM switches to the other ignition map. If the knocking stops, the
ECM advances the timing, in steps, back to the mapped point for that engine speed and load.
