1999 Dodge Durango 318 V8 P0138 and P0304: Idle Stuttering, Misfires, and Rain-Related Code Behavior
My 1999 Dodge Durango with a 318 V8 engine is experiencing intermittent stutters and surges at idle and while in gear. The check engine light appears to flicker or turn off during rainy weather, sometimes staying off for weeks before returning. I've already replaced the spark plugs, but the P0138 (O2 sensor circuit malfunction) and P0304 (cylinder 4 misfire) codes remain active. I'm now considering replacing the ignition wires next, though I'm also wondering if the oxygen sensor could be the root cause of these issues.
Start by checking the distributor cap, rotor, and ignition wires. Also inspect the coil pack for signs of wear or failure. It's unlikely that the O2 sensor is directly causing the misfire DTCs—especially since symptoms worsen in damp conditions, which points more toward ignition system issues.