What was found
FLIGHT 4439, DURING TAXI-OUT, COCKPIT AND CABIN FILLED WITH SMOKE & HAZE. RETURNED TO GATE AND DECLARED AN EMERGENCY. AIRCRAFT REMOVED FROM SERVICE. ODOR SMELLED LIKE ENGINE OIL. WHILE TROUBLESHOOTING FOUND NR 1 ENGINE TO BE SOURCE OF OIL ODOR & HAZE. ENGINE CARBON SEAL ASSEMBLY WAS REMOVED PER MM 72-25-25-000-801 FOR TROUBLESHOOTING. REMOVED AND REPLACED NR 1 ENGINE IAW 71-000-00. COMPLIED WITH ENGINE ODOR EVENT IAW ETN-EM-72-034. NO ODOR DETECTED. OPS CHECKED GOOD. AIRCRAFT RETURNED TO SERVICE.