Re: Ignition module Q\'s......
Yes, two degrees - at a time. But 2+2+2+2, one after the other retards it as needed.
When the knock sensor "hears" what it thinks is ping, it pulls the timing back instantly 2 degrees. But it doesn't immediatly go back advanced again. Another noise, another -2 -- and so on until the "ping" stops.
So the end result is it can pull the timing back fast, but the timing advances slowly.
As you drive the timing's always seeking the most advanced position - most efficient - but too much jumps it back a little at a time.
Yes, since the knock sensor is just a little microphone, a rattle can sound like a ping to it. I've seen several times an unrelated item - like a loose alternator bracket, even a deep socket left on the intake manifold accidentally, cause enough noise so it won't advance - it keeps pulling it back. It cannot retard at all, it cannot go back any further than intitial base timing, it just prevents advance.
Symptoms - low power, sometimes it's intermittant. Sometimes a hair puller!