Just found this problem, engine light on showed a misfire. Had shop double check all of the injectors and fuel pressure, all good. Install
a new fuel filter. Then did a new plugs. Thought it might be a spark plug wire, installed a know good one, no fix. Then swapped with the one next to it, still no fix. Replace coil, no fix. Replaced the ICM, no fix. Thought this could be related to the plenum problem noted here, not the issue, the engine is not using any anti-freeze. Tonight, I listened to all of the fuel injectors, all sound good.
Can a timing chain cause this kind of issue? It has never been replaced on this car and it has 165k miles on it. However, why just #4 misfire. Overall, the engine runs great at highter speeds, only misfires at idle.