As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
FLT 4379 EWR CREW REPORTED SMOKE IN COCKPIT DURING TAXI ASSOCIATED WITH ADVANCEMENT OF THRUST ON ENGINE NR 2 AND PERFORMED GATE RETURN. EWR MX PERFORMED ENGINE RUNS WITH PACKS OPERATING AND NO SMOKE OR SMELL NOTED. EWR MX SUSPECTS DE-ICE FLUID MAY HAVE CAUSED SMOKE/SMELL SINCE DE-ICING WAS PERFORMED PRIOR TO TAXI. ACFT WAS APPROVED FOR RETURN TO SERVICE.