I am on a mission to diagnose the poor idle problem of my 84 F150 I6, automatic Tfi IV ignition.
In park it idles ok stumbles a little but you can hardly notice it. As soon as I put it in drive its like one cylinder is along for the ride. Here is what I have tried. With No success.
· reset the initial timing to 10 BTDC (this was not easy since there is no timing mark on the balancer.)
· Replaced the tfi ignition module and connector plug.
· Vacuum is good at idle about 18 in.
· Performed a compression test 150 +/- 5 psi.
· Pulled the codes the only code I had was the Throttle position sensor code but I have replaced it twice and it will not go away and there is no adjustment.
· Removed the valve cover, made a tool to bleed down the valve lifters checked all but the #6 cylinder (coulden’t reach it with the tool) timed the bleed down, checked the gap after bleed-down everything is in spec. this pretty much eliminates the cam, lifters, and pushrods as problems.

At idle in gear I can remove the #2 plug wire with no noticeable effect but if I remove any of the other plug wires it gets real rough.
· Replaced the plug wires, cap and rotor
· Removed and inspected all spark plugs they all look perfectly normal gapped and replaced all.
· Tested the feedback solenoid on the carb. and it is working fine.
· Checked the carb vapor vent solenoid, its fine.
· Replaced the oxygen sensor.
· Reset the curb idle by the book.

Help! I am about out of ideas here.