Backfire.

[Jordan Hansford]

I have a 1991 sho 3.0 MXT I did a motor swap and put a 89 3.0 sho in it. I had to change the motor wiring harnnes for it to run. When you try to crank it it will backfire a couple times then crank right up and no skip. Under alot of power (4500-6500) rpms it will start to backfire and cut out. Get out of the throttle for a min or two and it will run fine. The oil smeels just like gas also. Just trying to run down the problem. Thanks

 

[rubydist]

so the oil smells like gasoline probably due to all the missing allowing gas to wash down into crankcase. continuing down that path will result in a lot of cylinder / ring wear.

there are a number of possible causes to your symptoms. please start by reading the codes. follow this link:
http://www.troublecodes.net/ford/

and let us know what you find. if you have trouble counting out the codes, just post a video for us.