I am having the code P0402 on my Ford Expedition. We have replaced the EGR valve, the throttle position sensor, the DPFE, actuator solenoid, and cleaned the EGR ports on the throttle body (which were clogged). The check engine soon light has been on, so after each part was replaced the check engine soon light was re-set. Now the car surges from around 500 rpm's to about 1000-1100 rpm's when you are in reverse or drive (slowing down, stopping). The vehicle acts like it is missing almost like it needs a tune up. The latest code is the P0402 (EGR excessive flow) and we do not know what else I can do. Does anyone have any suggestions?

 

If you are doing the work yourself you should first check all of your vacuum connections as they seem to cause the most drivability problems. The most common problem would be the one at the very rear of the intake manifold in a tight place to get to. The center of the vacuum elbow fails in the middle of the inside of the elbow. It's less than $5.00 at most parts stores.