A while back my 98 4.6 had a pretty serious exhaust leak where the EGR tube connects to the exhaust manifold. The fitting that screws on to the manifold had almost completely disinigrated <sp?> due to rust. Well I replaced what I needed to, to stop the leak, and recently I have been trying to diagnose the rough/stumbling idle that alot of F150's seem to be plauged with. My question is, would a leaking EGR tube (for almost 6 months...maybe more) cause an EGR to go bad? and I have since replaced my EGR valve position sensor as well.
Thanks in advance

 

your post as stated; there is no position sensor, only a DPFE.
Any problems with the EGR should have set codes and a CEL light.
What to you have?
A leaking EGR can cause rough idle but is not guarrenteed to be your problem as of now.

 

Do a search on IAC, lot of great info and pics. The idle air controller is a major source of idel problems on the Triton engines.

 

I'm with bluegrass on this one. If the EGR wasn't working, it would have set a code.

Try spraying starting fluid on vacuum hoses around the engine compartment at idle. Listen for any rpm changes. A common source of vacuum leaks is the rubber elbow where the pcv hose meets the intake manifold. I'm not particularly sure about your model and engine, but it probably has something to that effect. You could try cleaning the IAC valve as "torkum" suggested, as they are known for causing trouble, but I'd look for a vacuum leak first.

 

Roger that! I never had any codes due to the EGR tube leak, nor have I had any codes due to the low/rough idle, and I have a new IAC valve in place. I'm now on the hunt for vacum/intake manifold leaks. Thanks guys!