At my shop we have a 99 ranger with the 2.5. We cannot figure it out idles rough then smooths out. When you hit the gas it accelerates fine then stalls on decel and won't start for a little while unless you mash the gas. It throws a code for random misfire on cylinder 1.
It has a new timing belt, and component kit,idle air control, throttle position sensors, head has been replaced, both fuel regulators, cam sensor, cam sensor wires, 02 sensors, catalytic converter, plugs, plug wires, egr valve, egr switch, and egr tubes. We're stumped any help would be greatly appreciated.

 

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"
Key on
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.

 

When you say dampener is that the regulator on the fuel rail with the vacuum line going in?
If so we changed that. The fuel pressure goes up to 65 then immidiatly drops when key is shut off

 

No pressure regulator on the fuel rail with returnless system, that was the Pulse Damper.
There is only 1 fuel line coming to the engine bay, so no way to "regulate" pressure at the engine.
Where would a regulator send "extra pressure"?

The older Ford system had a Return fuel line and it was attached to a pressure regulator and also vacuum line, this system ran at 35psi pressure.
Above 45psi pressure valve would open and send "extra fuel/pressure" back to the gas tank.

The Returnless system uses a Check valve on the fuel pump, it is basically just a flap on the OUT of the pump, when pump is on flap is pushed open, when pump is off flap closes and holds pressure in the out line, fuel filter and fuel rail.
Check valve is part of the pump not a separate piece.

To check if the issue is at the pump find the flexible part of the fuel line back near the fuel tank, use vise grips or clamp to CAREFULLY clamp the hose, while someone shuts off the engine at the same time.
If pressure holds at the fuel rail then fuel pumps check valve is the issue.
If pressure still drops then issue is a leak in the fuel lines or injectors.

Do the Clear Flooded engine test
But turn key on and off 3 times before testing, that will build up pressure in the system, and if it is a leaky injector you will know it easier.

 

how long since you replaced the vehicles fuel filter

the fuel filter has a built in pressure relief valve , sounds like the relief valve is partially stuck open