1997 Dodge Ram 1500
magnum 5.9L Misfire. 150,000 miles.
To the best I can tell this misfire started with Check engine light reset. For years there has been an check engine light on and off, siting recirc valve issue. Usually fuel cap.
After this reset it began to (misfire) "chug-chug" at idle siting, #5 cylender. Cylender compression 135 psi all with in 10%
Changed in this order; First, spark plugs (no change), added fuel injector
additive to fuel (no change). Then replaced the fuel injectors with rebuilts (runs better but no change to misfire). Next the rotor, cap, spark wires (runs better yet, but no change to chug-chug misfire at idle, . At 1000 rpm and up it seems to runs smooth.
I purchased vehicle new. Synthetic oil change every 5k miles. K&N Filter kit.
Any suggestions as to the next step would be appreciated.