I just did a motor swap. I have an 88 mustang gt, and the motor went bad. I took the motor out of an 89 lx. i did not swap the computers or anything like that. I am having a hard time starting the car now, especially when its warm. it almost feels like a dead battery problem, but the battery is fully charged....and now all of a sudden, the car stalls out, and runs like crap...crap meaning, it misfires, and has no power.....anybody know whats going on????

 

i hope some of you more experienced guys out there can give me a word of advice......any would be appreciated

 

Did you swap out just the longblock, no electronics? Because the 88 is SD and the 89 is MAF and the wiring is a wee bit different and can cause issues when swapped out if you don't pay real close attention.

 

i swapped the longblock....not computer, pretty much just plug and play....new clutch and hardware.....should i switch computers and convert to MAF? is that whats causing my hard starting especially when warm....and now it seems like its backfiring and running rough.....

 

I think, but I'm not 100% sure, that if you left the 88 wiring harness intact that you should be OK with that. Check to make sure that when you put the distributor in, it was lined up correctly.

 

backfiring is a timing issue and the sd and maf problem WOULD cause rough running problems. I swapped my 91 motor for the FRPP 306ci motor and im still having problems similiar to yours. U have to tune the computer for the new engine to get rid of the problems for good. Some other guys will say " u gotta do this and that" and blah blah. But the computer is designed for the speed density, not mass air. So get someone to mess with ur EEC. Or go one ebay and find the right computer.

 

the hot start problem is probably timming, running high advance will cause the motor to crank slow when the motor is hot

 

i have the computer from the 89 car, and all the components....should i just go swap the computers and see what happens? keep the timing at 14BTC? im changing out the coil and the selenoid...plus the starter today.......

 

i messed with the timing, but no matter what i do, it still cranks slow when its warm....changed the starter, selenoid, plugs, wires, cap, rotor......i can't figure it out.....should i do a compresion check? any help on why this thing cranks and runs like crap would be much appreciated

 

have you cleaned these parts:

MAF
TB
PCV screen
IAC

Replace:

PCV valve
fuel filter


Run a bottle of fuel system clean such as Sea Foam and get 2 bottles to clean the whole car. What did you set the timing back at?