My 2006 toyota sequoia (87000 miles) wouldn't start one morning. It ran fine the night before. It actually did start, but sounded like it ran on 1 cylinder and made a awfull clanking sound, like the engine was coming apart. Initially I thought it broke the timing chain. Shut it off. Waited a few minutes and tried it again. It ran fine, like nothing ever happenned. It has run fine ever since. Had them electrically diagnose it, but it didn't show anything. Also the "check engine light" never came on.