I Have Pinging Noise Under Hood Of My 94 Isuzu Rodeo

I went to get pinging noise checked out and I was
told that I have maybe a piece of carbin in between
piston and shaft. And I was told to drive truck for a week or so and carbin could fall out and noise would be gone. Could this be a true?
when I start truck I hear the pinging noise and when I first start off driving I hear ping noise, but when I get on beltway and my gauge on odometer is near 2 or above I don't hear pinging noise at all.
Any advise would be greatly appreciated.


Thanks