Got a problem with my son's 1996 Explorer. 4.0 ltr, 4x4. Gas mileage has progressively dropped to horrible levels. 12-13mph on the highway. We are going do some basic stuff this weekend such as change fuel filter, air filter, etc.

However, I pulled the codes and am getting these three, even after resetting:
P0401 Insufficient EGR flow
P0402 Excessive EGR flow
P0133 EGR Oxygen sensor (I believe it was bank 1, sensor 1)

My initial thoughts are to replace the EGR valve and EGR sensor first. We are on a budget and don't want to start throwing one part after the next into it.

Any input? Thanks!

 

Before you replace anything, clean the valve and sensor and reset the computer. Quite often this will take care of the problem.

 

If you think it's EGR related, I suggest replacing the DPFE sensor. Fairly common problem. Also, check the lines going from the DPFE sensor to the EGR tube to make sure they are cracked/clogged.

 

Thanks for the replies. Was out of town all weekend so we tore into it Sunday evening.

Pulled the EGR valve, it looked surprisingly clean, very title carbon buildup, diaphram and valve seemed operational when we put a vacuum on it.

Removed the EGR sensor, the lines going to it weren't clogged but had a bunch of crud in them. The port going to the sensor looked about 1/2 clogged. Auto parts stores closed last night, we are putting one on today. We will drive it a bit and clear the codes. I'll post an update. Not sure if this is somehow tied into the P0133 oxygen sensor code or not.

Thanks.

 

REplace the Oxygen sensor, you should replace those about every 80,000 miles before they fail.