2002 Trailblazer, 207,000 miles. Driving home from work, engine started to sputter, SES and reduced engine power light. Pulled code P1514. Disconnected battery, cleaned throttle body not terrible, but dirty, and replaced MAP sensor. Buttoned everything back up and when I turned the engine over, it started for about 3 seconds, sputtering and what sounded like knocking then quit. I don't recall that there was any kind of noise, before the engine quit, as it happened pretty quickly. I have it at the shop and they are running diagnostics on it. Telling me it might be the timing chain, $2850. Are the timing chains known to fail on the 4.2 Vortec? Shop is going to keep it another day to try to rule out for sure that it is the timing chain. Anyone else have anything like this happen? Any advise would be great. I love my TB but with 207K miles, I can't see spending almost $3k for this repair if it isn't even worth that much.