Ford Repair: high idle, intake manifold gasket, gasket intake

Question
my 1990 bronco 5.0 e4od  (125,000 miles) will not idle down. codes pointed to tps and iac. i replaced both as well as the usual stuff i you might replace after buying a used vehicle. plugs, wires cap and rotor. i also replaced the throttle body to intake manifold gasket. intake manifold vacuum test did not indicate a leak, i also tested every piece of tubing and hoses nothing leaking. in park it will idle at either 1500 or 2100 rpm. it doesnt fluctuate its just one or the other.in drive it will idle around 900 to 1100 rpm, again not fluctuating it just seems to pick one depending on what day it is.(?) in reverse it idles at 850 rpm. what in the world is going on?

Answer
If you originally had an IAC valve problem, the computer may have learned an incorrect idle strategy. Disconnect the battery for five minutes to clear the computer strategies; after doing this it will take several trips to relearn the idle, be prepared for a low idle or stall at first. You can let it idle in gear for 5 minutes or so to aid in relearning.

Make sure the throttle cable or throttle shaft is not sticking. I have fixed several over the years that had sticking throttle shafts. Easy to check , with the engine warmed up push the throttle lever toward the closed position, if the idle decrease you know the problem.

The intake plenum gasket was a common leakage area on this engine, and make sure you don't have an air leaks, especially a stuck EGR.