Own a 1992 ford explorer. idles rough and surges. bucks at low speeds in low gears. have replaced fuel filter,o2 sensor and idle control valve. where to next?

I misstated because it actually was the HO2S that was changed. I've talked to numerous people, including shops and no one seems to know for sure. Everyone seems to just want to throw parts at it. I misstated because it actually was the HO2S that was changed. I've talked to numerous people, including shops and no one seems to know for sure. Everyone seems to just want to throw parts at it.

try checking all vacuum lines including brake booster hose and vent control hoses
check pvc valve for correct operation
check EGR valve and solenoid and wiring
from your description it sounds like an air/fuel ratio problem (vacuum leak or fuel pressure too low)
check fuel pressure with a pressure gauge
ford explorer is also a badged vehicle from another manufacturer ( mazda or nissan ) so ask around ( other service shops )to see if others have similar symptoms
check for moisture in the distributor cap or carbon tracking lines from the coil down the side of the cap try checking all vacuum lines including brake booster hose and vent control hoses check pvc valve for correct operation check EGR valve and solenoid and wiring from your description it sounds like an air/fuel ratio problem (vacuum leak or fuel pressure too low) check fuel pressure with a pressure gauge ford explorer is also a badged vehicle from another manufacturer ( mazda or nissan ) so ask around ( other service shops )to see if others have similar symptoms check for moisture in the distributor cap or carbon tracking lines from the coil down the side of the cap