HMMMMM interesting I seem to be having a very similar problem. Mine is a 96 4.0 ho auto. My Check engine light is on though and I got the codes read that it was throwing and it came up with cylinders 123456 misfiring, I said thats weird as hell can you clear them and see what happens, NOPE we are no longer alowed to clear codes (WTF). So I started out with plugs, wires, cap, and rotor.... No luck, on to ignition coil.... No luck, found a vacuum line disconnected plugged back in.... No luck, got a fuel filter from autozone gave me the wrong one gotta return and try that also gunna dump a bunch of Lucas fuel injector cleaner in the gas tank. (UNCC99xj) Tim is coming by gunna hook it up to his code reader and see what we get!