Lynn, it is likely that this seal was running broken for the last several hours, as the idle has been rough that long. It was just getting worse.  I will double check the CAS setting, but it always checks right where Tracy's manual says it should be.

 

The engine can run with damaged parts until the compression gets to low for fuel vapor to form from heat of compression. Could be a few more seconds, or months.

 

There is a last trip syndrome, where on the last trip the coolant heat is helping the heat of compression keep the engine running. Once the engine cools, it will never start again in any normal manor. Spinning it with 24 volts or heating the intake manifold may work, but otherwise the engine is done.

 

In my opinion, the three piece seals don't even look like they would work. The effective height of the top piece is too short and is nowhere as stable in the groove as a 2 piece (7MM tall) seal will be. If Tracy has a 2 piece 2MM seal that would make sense.  

 

Lynn E. Hanover