97 FORD RANGER WILL CRANK BUT WILL NOT START?

PLACED NEW MOTOR IN AFTER OLD MOTOR BROKE A TIMING BELT. HAVE BASICALLY REPLACE EVERYTHING, COMPUTER CAM SHAFT SENSOR COILS FUEL INJECTORS. CRAZY THING ABOUT IT, IT WILL START WITH A 6CYL COMPUTER IN IT TILL THE FUEL RUNS OUT OF THE LINE BUT REPLACE IT WITH THE CORRECT ONE AND NOTHING BUT BACKFIRING IF YOU EVEN GET THAT. REPLACED WIRING HARNESS ALSO. ANY Help WOULD BE APPRECIATED.

1999 ford ranger o2 sensor?

How many does it have, I have to replace it on my girlfriends truck. And I just need to know how many there are on it

Why is my truck misfiring?

I have a 2001 ford ranger 3.0 v6 with 100k miles on it. It's been misfiring but mainly in the low end of my tachometer. It was annoying and hard to accelerate without getting the car to shake. I changed the coil pack and all spark plugs. It seemed to work normal for about half a week then started acting up again. Now I'm contemplating on changing the spark plug wires also. Can bad wires cause misfires? I always thought they just effected gas mileage. Also if I replace them should I get OE or OEM wires or is it something simple enough it would matter what brand?

Under/overdrive problems?

I have a 1999 Ford Ranger that is shifting okay in overdrive but not in under. The light is not on. We have already checked filter. Can any one help me please?