1998 Ford F150 V6 Two Wheel Drive Manual 167000 miles
I have 1998 F150 4.2 standard shift with 167,000 miles. On a cold start the engine runs rough and backfires or dies. This continues for about 15 to 20 seconds and starts running and drives okay. While it is still warm it starts and runs and drives okay. If I disconnect the battery for 5 to 10 minutes, it will start and run properly at a cold start until it cools down, then the problem starts again. The check engine light has not come on at anytime.
Sounds to me that you have a bad coolant temp sensor, and disconnecting the battery clears the pcm of its memory causing it to start up untill it adjusts to proper fuel to air ratio. Also you may have a dirty MAF.