I have a recently acquired 96 4.0 with apprx 225k (mostly tow-behind). I had CEL and began having misfire when in drive with brake applied. Idle is smooth and driving pretty well on road. I replaced plugs, wires, cap, and rotor with no change. I pulled code and it was misfire cylinder one. Getting spark and fuel, but compression was very low (40). Any suggestions where else to trouble shoot. If its a bad valve, I don't know if its worth rebuilding head on something worth so little.

thanks

james

 

Try adding a teaspoon of oil and then performing the compression test again.

If the compression comes UP, then the problem is the rings. If it doesn't come up, it is likely a valve.