On the surface it reads like you are getting extra fuel in the intake manifold.
Rough idle after starting then smoothing out as extra gas burns off
Stalling after HIGH engine vacuum, deceleration, extra fuel sucked in and flooding engine
Then starting only after opening throttle plate to let more air in, "mashing on the gas"
Fuel injection computers all have a "Clear Flooded Engine Routine"
gas pedal to the floor and held down
Crank starter motor
Engine should NOT start, not even fire, if gas pedal is held down
Fuel injectors are shut off
As soon as you release gas pedal injectors will start again
TPS(throttle position sensor) gets 5 volts from computer, it sends back under 1 volt if throttle plate is closed, and over 4.5volts if throttle is wide open(WOT)
(just as a heads up, if TPS should short, it will send computer 5volts all the time, that will cause a no start, because injectors are off)
To start the "Clear Flooded Engine Routine" the computer must be on(key on), if computer reads above 4.5volts from TPS with engine at 0RPMs it will shut off the fuel injectors but leave spark on, gas pedal to the floor(WOT).
So when you try to start the engine there is no fuel so it will not start.
If it fires in "Clear Flooded Engine Routine", then there is fuel coming into the intake, check these things:
'99 uses Returnless fuel system, so fuel pressure at the rail should be 65psi, have you tested it and does stay above 50psi with key off?
Fuel pressure should stay for a few months, not just minutes or even weeks....months
Returnless has a pulse damper at the end of the fuel rail, it will have a vacuum line attached, check it, if there is fuel in that line then replace damper.
Next is fuel injectors, pull out #1 spark plug and check if it has black residue, rich burns, from leaking injector
You can also use "Clear Flooded Engine Routine", disable spark(unplug coils), crank engine using "Clear Flooded Engine Routine", pull out spark plugs wet spark plugs have leaking injectors.
Ford injectors get 12volts when key is on, the computer grounds each injector to open it, if one of these Ground wires should short to metal..............then injector would open.
Last edited by RonD; 01-06-2016 at 11:33 PM.