Have you tested your TAB/TAD solenoids to make sure that they're faulty? At the most, malfunction of either or both will direct air from the air pump to the wrong place, leading to a possibly-rich running engine. Have you checked & tested your vacuum lines and reservoir? Are those lines run to the right places and devices? Have you pulled codes? Just an FYI: The ignition coil is right next door to the TAB/TAD solenoids.

 

Personally I havent had the time to check my lines, I've only had the truck for a few days, but the Ford Dealership diagnosed that the TAB and TAD are bad. It would be a good idea to check things out but I'm pretty sure the solenoids are bad since it runs fine if you tap on them a bit.:scratchhe

 

Sig knows his stuff, don't discount his questions and advice. TAB/TAD direct air to the converter or the back of the heads. What you describe sounds very much like a vacuum leak. It is rare, but I suppose these solenoids could be cracked and allow a vacuum leak. A quick test would be to plug the vacuum source leading TO the TAB/TAD solenoids. If your problem goes away then start looking at the vacuum lines, then the solenoids. I used a small hand-held vacuum pump to test the vacuum lines on my '92 F350. Most every one of the hard plastic lines tested bad as well as the EVR. After replacing them and verifying each circuit held a vacuum the idle quality and MPG has started to slowly rise.

As a side note I joined the 21st century club by re-routing the vacuum line to the PCV valve to the center manifold tree and replaced the upper to lower intake gasket when I had it apart. My idle has dropped to ~650 rpm just like a new truck. 17 years old and 150K miles it runs like a top again!

Randy

 

I definitely wont discount Sigs advice, I'll check on all the vacuum lines and i'll plug those solenoids then go from there.
Thanks!