The way the computer regulates the EGR value is in my mind overly complex,
[The computer drives a differential pressure regulator, (connected between
raw manifold pressure and the EGR valve), with a variable pulse width
signal, the translated variable pressure created then modulates the EGR
valve, this in-turn regulates the amount of recirculated exhaust gases ... I
told you!], to simplify a bit, I suggest you check/change all the vacuum
hoses involving this damnedable system. I also think there are many other
sensor used by the computer to come up with the modulating signal, so don't
think EGR only.
I'm chasing the same problem on a '00 Ranger. If I clear the code the
problem stays away for several hours but always returns, (Isn't the "Check
Engine" light system the most feeble bit of engineering you've ever dealt
with? It's designed to scare you and send you running to your
dealer/mechanic ... don't get me started ... it's a highly flawed system).
My EGR valve and hoses are perfect, I've got to check the vacuum switch
next, but I've also started to look at other sensors that can effect the EGR
system: like the O2 sensors, also MAF and MAP sensors. I have been led
astray by OBD II codes before.
Also don't overlook the air filter, plugs & wires, change the gas you use,
also put in a can of injector cleaner in the next two or three tank fulls.
Clear the code and see how long the "CE" light stays off. What do you have
to lose. These are easy simple things too.
I've been driving the ranger daily for about 6 months with this problem and
it runs perfect, no stumble, hesitation, plenty of power and pick up so I
don't think you are causing any harm by driving with this problem. I do
notice a barely perceptible chugging when going at a steady medium speed
(50mph) in OD. Probably caused, (or not), by the pressure switch; its the
only damn thing I haven't checked.
I wish I could say: here's how you fix it ... but Alas Poor Yorick ....