8f032b14_r_Visible_Exhaust___NCTCOG_org__Possible_Causes
[Engine Type] Diesel [Visible Sign] Black or Gray Smoke [Diagnosis] Smoke may be coming from incomplete fuel combustion [Possible Causes] 
Faulty injection system Clogged air filter Wrong grade of fuel Timing may need to be adjusted Engine overheating Oil Leaking on exhaust system
Common Causes for Smoking Vehicles or Visible Exhaust - NCTCOG.org
Possible Causes