Egr Valve
(1) Check the EGR valve for sticking or carbon deposits.
If such conditions exist, clean or replace the EGR valve.
(2) Connect a hand vacuum pump to the nipple of the EGR valve and plug other nipple.
(3) If there is vacuum leakage, replace the EGR valve.
(4) Blow air in from one passage of the EGR to check its condition