88 k-series, 4x4, 5.7. During acceleration it knocks. Kinda like like low octane knock, but not as deep as bottom end knock (thank God). Problem is I've never had low octane knock in 250K miles. A friend who is a mechanic for UPS said it might be timing. Makes sense because of the way it sounds. It's not throwing any codes though. All suggestions welcome. Rockfish
If you have not had any ping/knock in 250K, you are very lucky as those engine are linda prone to knock on 87 octane unless the timing is retarded a lot. GM got it to tolerate 97 by used a spark knock retard circuit with a sensor on engine. You might check its operation. The sensor is usually in the block drainplug hole on bottom passangerside of block. I have a 89 4x4 burb with 176k on it and it does not ever knock but it has not had 97 octane in it for 16 years either as I discovered early in its life that it could be made to run much better with better gas and a little "tweaking" The SnoMan
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