Rough idle and stumbling
 

I just bought a used 2001 Ford Ranger 3.0 4x4 with 147k miles. It ran perfectly fine on the test drive and on the 2 hour drive home with no lights on and then about 2 days later I went to start it up and it idled REALLY rough and juddered severely upon acceleration. Then it started stumbling at around 45-50mph and the rpm would drop to ~1500 and I had no throttle response until I lifted off the throttle and that seems to sort it out somewhat although it runs "smoother" the higher it is in tge rev range. It feels like a misfire. Can a misfire just happen out of nowhere? I unplugged the plug wires and cylinder 1 didn't make a difference in how it ran. Any input would be greatly appreciated. Thank you.

Welcome to the forum

Did you get any gas since you got it?

Could be you got some "bad gas", which means too much water in it, all gas has some water, when there is too much and a vehicle sits the water settles to the bottom of the gas tank, so when you start it the fuel pump sucks in that water/fuel mix which does burn well

You can add some HEET or Octane Boost to the gas tank, its ethanol, ethanol can bond to the water, gas can't, when bonded with ethanol the water can be burned, although with very low power output, but at least it can be burned, lol.

Could be coil pack is starting to fail, if its the original coil pack from 2001 then its highly likely because 2000-2002 3.0l coil packs did have issues, but would be surprised if it is original because of that.

Was the engine COLD when you got there for the test drive?
Or was it already warmed up?

Cold starting means engine needs to be Choked, that that system relies on ECT sensor and computer working well

The engine was very cold when I test drove it. The temp. A few days ago was -60. My parents told me to put heet in the tank last night and it actually ran a litttle worse this morning. And today in my college parking lot it stalled twice, wouldn't restart. I'm pretty sure it the original coil pack, but I'm not sure.