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Knock sensor & retarded timing

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

Reply to
Lance Morgan
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I know it's possible for engine mechanical noise to be detected by the knock sensor, but I would think if that were the case, the noise would likely be audible with the engine at that speed - are you hearing anything unusual?

Reply to
Robert Hancock

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