1996 Ford Ranger P0302 Code: Rough Idle After Cool Down, Solutions & Diagnostics

I own a 1996 Ford Ranger 3.0L automatic 2WD with over 215,000 miles. The vehicle starts smoothly and runs fine during normal driving conditions. It reaches operating temperature without overheating, and the engine performs well under load. However, after parking and turning off the engine for 15 to 20 minutes, when I restart it, the idle becomes rough. Once in gear, the drive feels uneven—like only five cylinders are working. A P0302 diagnostic code appears at this time. After allowing the engine to cool completely (for one to two hours), I clear the code and restart. The vehicle runs normally again until the next shutdown. This cycle repeats: after 20 minutes of idle, restarting causes the same issue. I have already replaced the spark plugs, ignition wires, coil pack, and fuel filter. Additionally, I've added a bottle of injector cleaner every 3000 miles during oil changes—this did not resolve the problem. The recurring nature suggests an underlying issue related to fuel delivery or ignition timing, possibly tied to cylinder #2. I'm seeking advice on how to properly diagnose this P0302 code in my 1996 Ford Ranger.