So this truck has intermittent stalling and stuttering not going over like 20 miles per hour so I did what everyone says not to do and I chased the problem with parts but I did some test first so the first thing I did is replace fuel filter plugs and wires and the ingnition coil that didn’t help then I changed iac,Pcv and did a smoke test for any vacuum leaks didn’t work so I cleaned throttle body still no luck so I hooked a obd2 reader up and fuel trims was out of whack I was getting a random Mis fire in #4 lime every couple weeks then misfire multiple cylinder but this is all intermittently it would run perfect for days on end checked all o2 sensors tested all injectors disconnected cats to see if maybe they were clogging out the only thing that changed it for about 2 weeks was a maf sensor I changed but only temporarily so I put another one same thing about 2 weeks then started again

 

Welcome to the forum

O2 sensors are the only sensors that NEED to be replaced, every 100k miles or 12 years, at 20 years old you should be putting in the 3rd set of O2 pretty soon
O2s don't set codes as they wear out, only well AFTER they wear out
And as they wear out they cause the computer to run engine Richer than needed(false lean), so waste alot of gasoline, $$$ out of your pocket

Things to check on OBD2 reader
ECT sensor, coolant temp, should read outside temp on cold start, then read about 175-185degF after full warm up
ECT sets the Choke so can cause poor running if No Choke, or too much Choke

Throttle sensor(TPS), key on engine off
Should read 16-19% with foot off the gas pedal
And 90-92% with pedal to the floor, WOT(wide open throttle)
If under 90% Google: Ranger throttle cable mod
Easy fix for stretched throttle cable

When engine is acting up find a place were you can run for a few seconds at WOT, foot to the floor, see if it runs better
WOT(90-92% from TPS) tells computer to ignore O2 sensors, and most other sensors, Driver wants POWER not best MPG, so computer uses air/fuel mix tables in memory for best power
This can tell you if computer is getting bad data from a sensor

Misfires cause air/fuel mix to jump around, air/fuel mix doesn't cause misfires, in most cases
When a cylinder misfires no Oxygen is burned
O2 sensor ONLY see Oxygen, not fuel
So misfire causes higher oxygen levels in exhaust, "lean condition", so computer adds more fuel to that Bank of the engine, high fuel trims

When engine is warmed up and idling, unplug the 2 wire connector on IAC Valve
Idle should drop, engine may even stall, either is GOOD, it means no vacuum leaks
If idle doesn't drop then you have a vacuum leak somewhere

 

When I try and WOT the rev limiter won’t let it go over like 3000 rpm