Can a piezo crystal KS (91 Saab 900) pick up bad rod or wrist pin bearings, or are they (intentionally) outside the KS's frequency range?
When rod or wrist pin bearings just start to go bad - not even sure it's audible yet - do they generally do it at low, mid, or high RPM?
Have a reproducible bucking prob @ 2800 RPM (have done a fair amt of ignition and fuel sys testing): timing is abnormally retarding around that RPM, staying retarded - not trying to readvance - until I get above 3K RPM (car pulls strongly to redline)
Ignition advance controlled by computer