1996 Ford Escort Fuel Economy Issues: P1443, P1130, P1131 & P0171 - EVAP, O2 Sensor, MAF Diagnosis

I own a 1996 Ford Escort with a 5-speed manual and 1.9L engine. Despite replacing the spark plugs, ignition wires, coil pack, fuel filter, and installing a new air filter, I'm still experiencing poor fuel economy. The car runs smoothly but exhibits a sloppy idle—dropping to 500 RPM, stalling briefly, then rising to 1000 RPM before settling again. This pattern repeats intermittently. Using an OBD2 scanner at AutoZone, I retrieved the following diagnostic trouble codes: - P1443: Evaporative Emission Control System - Vacuum System - Purge Control Solenoid or Purge Control Valve Fault - P1130: Lack of Upstream Heated Oxygen Sensor Switch - Adaptive Fuel Limit - Bank 1 - P1131: Lack of Upstream Heated Oxygen Sensor Switch - Sensor Indicates Lean - Bank 1 - P0171: System Too Lean (Bank 1) I inspected the EVAP system and found no vacuum leaks in the purge sensor, solenoid, or hoses. The purge solenoid activated when connected to battery power, and resistance readings for both purge sensors were within specifications. After clearing codes, I monitored the first upstream oxygen sensor signal voltage—initially appearing stable at around 0.45V during warm-up. Upon restarting and warming up, a MAF (Mass Airflow) error appeared. I swapped in an airbox and MAF unit from another 1996 Escort, cleared codes again, drove to the store, refilled the tank, and checked for errors upon returning home—no codes were present. The sloppy idle has also resolved. Questions: - Could the O2 sensor error codes (P1130/P1131/P0171) have been triggered by a faulty MAF reading? - Is it possible that P1443 was caused by a loose fuel cap, and only required clearing after tightening? I’ve inspected all EVAP components thoroughly with no leaks. Would the ECU automatically clear this code once the fuel cap is secured? I’ve now filled the tank and will monitor fuel economy over the next few days to see if any codes return or if mileage improves. Any insights from owners of 1996 Ford Escorts with similar symptoms would be greatly appreciated.