On Tue, 08 Dec 2009 13:18:17 -0800, Oren wrote:

On Tue, 8 Dec 2009 12:04:40 -0800 (PST), Larry Fishel
wrote:

On Dec 8, 2:42Â*pm, "JoeSpareBedroom"
wrote:
OK - so now that we've established that there's a broken spark plug
(assuming the mechanic's telling the truth), what are the various levels of
horror which could result from further diagnosis?

Worst case is something like:

The timing belt/chain is worn and skipped a tooth (just fixing this
could be a few hundred).
This caused the pistons to hit the valves, damaging the valves, a
spark plug, head, pistons and possibly even rods.
Broken bits of valve and/or spark plug gouged the cylinder walls.


How would slipped timing cause the piston to hit anything? Never heard
of such a thing.
It happens a LOT on engines that are "interference" engines. The
valve is opened by the cam when the piston comes up - the piston hits
the valve and bends it. If it hits often enough, ot just the right
way, the valve head can break off and bounce around in the cyl.
The valve can also crack or break the piston.