New problem that I can’t solve. Suddenly, and without any outward indicators, I started getting massive knock counts. I’m talking 50, 100, 200 quickly counting up on the monitor. Started toward the end of my last test drive (about 100 miles on L31 engine swap); low rpm, low kpa. Seemed to run fine. It now does it intermittently, but consistently. Sitting and idling, closed loop or open, will suddenly start counting up. Then it will stop and be fine for 30 seconds to a minute, then back to counting up. No noticeable change in engine at all. I checked header flange and collector bolts. Checked the knock sensor, plug and wire; all appears good (sensor reads 3.9K). Pulled a spark plug and it looks fine. Double checked the static timing. Ran through the factory manual diagnostic for knock sensor; DVOM reads 4.9 volts, key on engine off at knock sensor plug (sensor unplugged). With the knock sensor unplugged (engine on), it shows no knock counts, but still retards timing when I punch the throttle. Swapped out ECM and no change. Could this be the memcal? I don't have an "extra" memcal so I can't swap out to check.

 

Have you done any careful listening for something like a loose rocker or bent pushrod?

 

I have and don't hear anything obvious. Admittedly, I really don't know what I'm listening for. These Bosch III injectors are so loud, it's hard to hear anything else! How obvious would the valve train noise have to be to create false knock? BTW, this is a brand new Chevrolet Performance crate engine, not that that guarantees anything.

 

Really need a lab scope so you can look at the waveform from the knock sensor and also the PWM output of the ESC module. Could be a bad sensor, could be a bad module, could be noise from something else entirely like the ignition system.

GD

 

I am leaning towards one of the three things you mention. Brian is sending me a swap-out memcal so I can either confirm or eliminate that variable. If that doesn't provide an answer, I thought about trying to run an alternate wire from ECM to knock sensor to rule out ignition noise polluting the signal. Seems to me that if it was something mechanical then it wouldn't be intermittent.

 

Swapped in the new memcal from Brian and that seems to have fixed it. One knock count after 5-10 minutes, and that was there on start-up. Just to be sure I swapped the old memcal back in. Over 150 knock counts in 30 seconds. I think that's pretty definitive. BTW, tunedperformance is the bomb! Shipped me a memcal 2-day Priority so I could troubleshoot. Of course, now I have to buy the new memcal from him, but that's fine. I'm just glad it's fixed.