My ex's 1999 Subaru Legacy (4 cyl, 126K miles) began making some nasty noises in the motor a week ago. She drove it 2 blocks and it's been sitting in the driveway ever since, while she ponders what to do. Except for warranty work, It's been maintained by one very competent mechanic throughout its life. He's hesitant to mess with it because he says that evaluation could require major engine disassembly which could cost so much that no sane owner would want to even go that far just to find out that the car is toast. Car is in otherwise excellent condition.
So, ***if*** we were dealing with a spark plug which was broken due to incorrect length, wouldn't that have happened almost immediately after the plugs were installed? Assuming yes, what else are we left with? Right length, wrong plug (temperature)? Wrong torque? Defective plug? Seems like some things could point to the mechanic, as unlikely as that seems based on his track record. Or, manufacturer.
Any other thoughts on this?