DS shows minor KR -- is it real?

[Fred 86 GN]

During a run, this happens 2-3 times, typically around 4200-4400 rpm, in second and third gear mostly. The A/F ratio drops below 9:1 on the DS screen (what the ECM is calling for, supposedly), and the next half-dozen frames show the following KR amounts -- 1.8, 1.2, 0.9, 0.6, 0.3. Sometimes it only gets part way down then starts again -- 1.8, 1.2, 1.8, 1.2, 0.9, 0.6, 0.3. Sometimes the 1.8 value causes a "knock count", sometimes not. So I only see 1-3 "knock counts" in a run typically.

Does not seem to occur during shifts (those happen around 5000rpm and the engine falls back to 4000rpm or so).

Anyone else see this sequence?

Should I be concerned?

O2's can be 760 to 820mV during this event...doesn't seem to matter.

Thanks,

 

[Brooks]

Hi Fred, when that happens with my car I'm fairly confident it's real knock.

One quick way to tell whether it's real or not is to toss a couple gallons of Xylene or race gas in the tank and make another run. If the knock retard goes away than it was real. If it's still present I would look at motor mounts and the downpipe location to ensure nothing is making contact where it shouldn't.

Charles Brooks

 

[BEATAV8]

I've seen similar data as well with my car. This thread explains why you'll get knock retard sometimes without knock counts:

http://www.turbobuick.com/forums/showthread.php?s=&threadid=38768&highlight=knock+retard+count

I would treat it as real KR.