Having problems with your 2002 GMC Envoy ?
When truck sits overnite and started it has a tapping sound,is this normal?
\015 When drven 2-3 miles, tapping stops, is this a lifter loosing prime?\015
I imagine what you're hearing is piston slap. While that sounds bad, it's not. For a variety of reasons, manufacturers have been using pistons that are shorter and shorter in height. As they wear (we're talking a very small amount of wear here), the piston tends to rock in its bore. So you're hearing the skirts slap the cylinder walls. This is not harmful, just annoying. The sound goes away after the piston absorbs some heat, and thermally expands.
Repair Help & Product Troubleshooting for 2002 GMC Envoy
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