Funhawg

Ok so I bought a use engine, did a valve job and replaced all gaskets and seals. I researched and found out how to properly time the engine. It starts and runs but roughly and with misfires. Any ideas?

Funhawg

The engine is a 4.0 out of a 99 xj going into a 97 xj. Are there any cpu differences?

tjwalker

Any codes? Even if no, put a code reader or a scan tool on it as there could be "pending codes".

Lots of variables with an engine install. Did you use fresh plugs, wires, cap, rotor?

Test fuel pressure. For your vintage, you need 49 psi, plus or minus 5 psi for the engine to run correctly.

Do you know the history of the engine you installed? When was the last time it ran? A simple compression test is a good "snapshot in time" of the internal condition of the engine.

The above are basic things but must be ruled in or out before moving onto other possibilities.

Good luck and keep us posted!

Funhawg

All new plugs wires cap rotor. Didn't do fuel pressure check but did replace fuel pump. Good compression anywhere between 136 to 152 psi