Ok someone else in the girlfriends family swapped out motors on her moms mustang its a 2002 mustang with a 3.8. The one motor was bad so they bought a re-manned motor from a company and swapped them out. Now they have it all together, its running but very poorly, It has a good miss in it at idle. When you put it in drive it gets real bad. You can take it down the road and all it does is pop and crack and lacks in the power area. We was thinking injectors or the timing is out. WE think injectors because we were told when they were putting it together they were messing with the injectors prying on them or something, and if it wasn't that it has to be timing. What are all your opinions on this? Oh by the way when I first looked at the car the Check engine light was on so it was throwing the code P1258 I think it was for the air/fuel but we reset the computer and now its not showing any codes...Any help appreciated...

 

My guess would be that they put the plug wires in wrong and so the firing order is messed up. As you say wouldn`t do any harm to check the base timing.

 

Run a compression test, make sure the crank trigger isn't missing any teeth, and make sure the coils are good.

 

Changed out injectors still the same problem. Were gonna go try to rent or borrow a timing light to check the timing, as well as double check the firing order to the wires hopefully there just on the wrong way. We tried two different coil packs and nothing changed.

 

The timing is entirely controlled by the computer, so checking it isn't really going to do a whole lot of good.
Look the firing order up online, and if it's off correct it. If it isn't off, then check the compression and check the crank trigger (what the computer uses to set timing).