1996 993 with the typical random misfire codes on all cylinders. We went through all the typical stuff, wires, plugs, caps, rotors, coils, and also found leaks on intake boots, all of which improved the running of the car, but didn't fix the CE light. Put in a new flywheel and the CE light is gone. The old flywheel was out of spec, but why does an out of spec flywheel cause a check engine light.

 

This may explain it


https://rennlist.com/forums/showthre...ht=misfire+302

 

That thread explains it but its kindof long..its a pretty simple idea. A DMF has two parts ; the outside rim and the inside surface. There is a spring/buffer cushion between the two. The idea is that the DMF will absorb shock from the drivetrain to the engine and visa versa. If that cushion gets worn there becomes extra slop between the two ; you now can have the center part moving around and causing the outside to jerk around a tiny bit ;that tiny bit causes a bit of jerkiness in the rotation of the motor that gets read as a misfire.

So a worn DMF can cause misfires. This is why, if you shut the engine off, a worn DMF will rattle...its the center part that keeps rotating a bit when the crankshaft stops.

That is my current understanding anyways..... :-)

The RS clutch does not have this issue since its like a conventional clutch ; the flywheel is one piece with no buffer. However it also does not absorb any vibrations/variations so at times the transmission will rattle when idling in neutral with the clutch out..

Cheers,

Mike

 

Rennlist. I wish I read a bunch before buying my 993 in 2004. The dealer covered the cost of a new clutch and flywheel and went with the DMF as well as regular clutch. If I knew, I could've gotten the rs clutch and LWF for free.