If you experience cold starting problems, stalling at idle, or hesitations during acceleration, it may be the idle air bypass valve. This valve helps the vehicle idle steadily and run when the accelerator pedal is not pressed.
Car Problem Reports
Ford Ranger Hard to Start Cold, Stalling at Idle
Ford Ranger Problem
Engines Affected: 2.5L 4 Cylinder, 3.0L V6, 4.0L V6
Average Mileage: 166,800 mi (130,000 mi - 215,000 mi)
Visitor, 1998 Ford Ranger, 2.5L 4 Cylinder, 215,000 mi
doesn't like the cold weather. idles very low and won't stay started. when it warms up, it's fine
Visitor, 1998 Ford Ranger, 4.0L V6, 145,000 mi
Truck hard to start when cold. Replaced aic valve mass air flow sensor and battery. Truck still stalls and lacks power.
Visitor, 1998 Ford Ranger, 2.5L 4 Cylinder, 130,000 mi
Engine begins to rough idle while stationary, at a light etc., but If the gas pedal is given a quick tap it will smooth out and continue to run, otherwise it will stall. Restart has not been a problem so far and the number of occasions has been minimal. Has not been in for repair yet.