Occasionally my scanmaster will show knock retard at idle and increase dramatically at very light throttle. Comes and goes. It's time for new plugs so I'm doing that soon but just wondering about the mystery knock retard.

 

Your valve train could probaly cause "false knock". No LT4 knock module?

Who tuned it for the blower? Is it a 2-bar MAP tune?

 

Yes, I have an LT4 knock module. Have Jesel shaft mount rockers. Tuning done by local performance shop. No 2 bar tune.

I've just noticed this recently. It will do it for a while and then clear up. It will show 0.1-0.2 degrees of retard at idle and will jump up to 1.0-1.4 just blipping the throttle. Even more just pulling off from a stop.

Just wondered if this was a known phenomenon.

 

A misfire generally won't be interpreted as a knock.

Is it possible your blower has become a bit noisier?

 

It's possible. I think that you answered my question though. Thanks.