My 95 ford ranger 4.0L idles rough, usually at stoplights. It only does it when the motor is completely warm, and its intermittent. Ive checked plugs, wires, AF, FF, IAC, MAF, EGR, PCV, purge solenoid, and looked closely for vacuum leaks. I checked the evaporative purge solenoid by disconnecing and plugging it from the intake manifold. Still have the same problem. Also the check engine light is on with codes
P1444 purge valve solinoid output low
and also lean bank 1 and 2.
Continuous Memory Diagnostic Trouble Code (DTC) P1444 indicates that Self-Test has detected a PF sensor circuit input below the minimum.
- PF sensor circuit short to PWR GND.
- VPWR open circuit.
- Damaged purge flow (PF) sensor.
- Damaged PCM
So it would appear to be a bad PF sensor or a problem with the circuit.
Regarding the lean codes on both banks, those can be caused by several things, you are on the right track looking for vacuum leaks, maybe you can do the propane gas trick where you apply the gas all around the upper engine area; if there's a leak the gas will get sucked in and the idle will even out and/or increase. You should also think about re-torquing the upper and lower intake bolts, sometimes the gaskets are sources of air leaks. Change the fuel filter if it has been a while, and clean the MAF sensor:
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