Need Ideas

The past few days when I started my truck in the morning (Temps about 20F), besides the standard Chevy knock, I had what sounded like someone tapping a screw driver handle off an empty coffee can coming from the motor. It normally just disappeared after it ran for 30 seconds or so and reverted to the standard not so loud piston slap that GM can't seen to get rid of. Well earlier today I ran out for lunch (temp about 30) and I got the slapping again, I let it run for a few minutes, it didn't stop so I started to drive. The slapping continued for over two miles, loud enough I could hear it in the cab over my exhaust and the radio. The more throttle I gave the more it slapped (obviously). It took over two miles for it to stop. It's not a gradual stop it just goes away, period. Any ideas what this is? Could a valve be sticking or could it be finicky heads crying about cheap gas? Any ideas would be great, sounds horrible!!!

Hi, This Is My First Post Very Valuable Info Here. Ok I Have 2001 Silverado 4.3 Engine And Year Ago I Had The Same Problem, I Was Ready To Put Apart The Engine But, A Change Of Spark Plags, Oil, And Lucas Solved That Problem Since That I Had Not Hear That Sound Anymore .

How many miles?

Have you checked your oil? Level OK, last oil change, correct weight? May be a quick and easy place to start before getting in too deep.

Many people claim that switching to Mobil 1 full synthetic dramatically reduces/eliminates piston slap.