EGR Valve

[circmand]

I am no expert I just know my circumstance but I have read here that the EGR valve can get stuck open or closed or in between maybe this can affect whether you get more or less mileage. Perhaps one of our more learned members can chime in

[bartmanS4]

If your egr is working properly, then you should not have noticed ANY gains. The egr only operates during cruise conditions. It does not operate at idle because idle quality would be greatly affected. It does not operate at full throttle because Ford knew you want full power when you put the pedal to the metal. The reason they do it at cruise is because it has very little effect on performance when you are cruising down the freeway at a light load. when you smash down on the accelerator, the egr shuts off. In my 94 ranger the egr uses a DPFE (Delta Pressure Feedback EGR). In that, there is an orifice inside the tube that goes from the manifold to the throttle body. There is a silicone tube on each side of this orifice that goes up to what looks like a map sensor with two lines going to it. When the egr starts to operate, there is a pressure difference within the tube on either side of that orifice. This is how that 'map' sensor verifies that the egr has proper flow. In addition, when that sensor sees flow of the egr at cruise the computer knows that it is an inert gas and backs off fuel to keep a proper AF ratio, lower NOX, and save fuel. So if you noticed any power increase from blocking off your EGR it was not working properly. It most likely had a sticking valve that was allowing exhaust gasses back into the intake at all RPM. This would greatly affect power.

I found this write up that make a lot of sense to me.