I have a 2003 Ranger 2.3L that I have completely rebuilt. Scan tool shows consistent idle speed and no misfires. However, the engine shakes terribly. Is it possible to get the flywheel on wrong?
There is no explanation for the shaking/vibration. The motor mounts seem solid (i didn't actually check them when the engine was out-my bad) but putting a jack under the engine does not show any looseness or movement.
I have double checked that the cam/crank timing is correct.

My theory is that the flywheel is either on wrong or out of balance. (My past experience is that the bolt holes only allow the flywheel to go on one way)
A friend of mine said he had a similar issue, and the flywheel was "off".

Thoughts anyone?

 

Engine is internally balanced for true
Flywheel is externally balanced for true
So it can't go on the wrong way

Its possible a balance weight came off the flywheel

What about harmonic balancer, crank pulley

The 2.3l Duratec is a Mazda L engine, L3-VE
Article here on it: https://www.motorreviewer.com/engine.php?engine_id=109

From above article, "There is a two-piece housing with two balancing shafts inside at the bottom of the block. It is a cassette type balancer unit driven by a gear attached to the crankshaft that rotated at twice the speed of the crankshaft to offset the secondary inertia force"

4cyl engines only fire every 180deg, so will vibrate more at lower RPMs than a 6 or 8 cyl, they need to idle above 750rpms