I took my 2000 Jimmy to my mechanic as it was making a strange scraping
noise, sometimes it resembles a slight "ping". It mainly made this noise
after being fully warmed up. At first, it only made the noise while
accelerating at average speed while making a left turn. I has since
begun doing it when acceleration straight ahead, or turning right,
though not as predominantly. He did find a TSB dated December, 2002
#00-06-01-023B, which describes this as being an "a natural torsional
vibration in the cam drive system, loading and unloading of the balance
shaft and gear drive assembly". The earlier TSB on the same issues
appeared to describe it as "the spark, rattle-type noise may be caused
by torsional vibration of the balance shaft". GM insists that "this
noise does not present any durability risks to the engine or any of its
components". This, to me, sounds like another GM sluff off. They screwed
up again, and are making the consumers pay the price for future R&D.
Enough ranting about GM. Has anyone enountered similar symptoms that
were not related to the above noted TSB?