engine knock

I have a 2003 Silverado with the 6 cylinder. When driving at 20 to 40 mph, the engine idles at around 1000 to 1200 rpm. When I accelerate, there is a hesitation and engine knock. Any suggestions?

When you have a knock in these 4.3L engines that means that you have a lean fuel condition, usually caused by clogged fuel injectors or a restricted fuel filter.

Run higher octane fuel and run a couple tanks through it with a good carb/injector cleaner. That should clear it up.

Usually, the computer will adjust the timing to eliminate the knock, so You may need a knock sensor.