Car is 2003 Dodge Durango RT with the 5.9L Magnum V8 (99,000 miles). Last Saturday about 3 minutes after turning the truck on (all running smooth) truck out of nowhere begins hesitating, sputtering, etc. I pull over and 30-45 seconds later all returns to normal. No check engine light, oil pressure is good, etc. I continued to drive and diagnose this week. Doesn't matter if engine is warm or not, first 2-4 minutes all is fine, then comes the 15-40 seconds of engine fits, then all is good for hours. Found this thread on the Dodge.com thread where someone had experienced this very same thing. However, they got check engine light code: P0132 O2 Oxygen Sensor Circuit High Voltage (Bank1, Sensor1). [url=https://dodgeforum.com/forum/2nd-gen-ram-tech/256614-help-hesitation-when-engine-cold.html][/url] Long story short, I replaced my upstream 02 sensor and that was the culprit. Wanted to put this here in case someone in the future was experiencing something similar. The above thread saved me a lot of time and money diagnosing this without a check engine light to work from. Someone on the forum explained what was going on: [You have an O2 sensor problem. The truck ignores the o2 sensor for warm up, called open loop. When you hit closed loop the heated o2 sensor attempts to keep the truck running at a very specific air to fuel ratio. The problem with your o2 sensor is that it is failing and not reading correctly. When you step on the gas, the extra heat from exhaust heats the o2 sensor and it starts to read correctly again, for a brief time. When you let off the gas, the o2 sensor cools down and throws fits again. Specifically it is the o2 sensor that is closest to the engine before the catalytic converter (the big bulgy thing in the exhaust right after the 2 down pipes connect at a Y). It's called the precat o2 sensor.] Not sure how 02 sensors work, but mine was doing something weird. Hey, it is a 15 year old 02 sensor. Hope this helps someone in the future. Good day all.