Originally Posted by gearhead351

I have solved my issue! I had a tiny fuel leak that was introducing air into the system. The fpr return line was the culprit. The hard line with the nut on it has a tiny rubber seal INSIDE the nut was trashed. Few bucks at ford my truck runs excellent. The smooth idle has returned. My truck always ran good in the throttle but that seal was my rough idle maker.

That seal is inside that nut. Make sure you tighten the nut down firmly; it actually seals the threading up against the fpr the rubber seals the line. I'm very happy.

7.3 return line seal - Google Search

Originally Posted by chrislorl

Well I too have had a great change. I replaced my Throttle Position Sensor. In my truck it is the whole pedal assembly. What a difference it made. But I still have a slight shutter when driving. Could you give me some more details on where this o-ring is that you replaced, maybe a picture.

Thanks and Happy Fathers Day if your a dad too.