Originally Posted by
haz87
It could be a multitude of things, but I'd start with ignition timing if the distributor has been disturbed (or if you swapped it from your original engine). Then cam timing.
Then it will be a setup of the carb - just cause the engines are the same, doesn't mean they breathe identically so it may have put the balance out of whack.
Even the MK2 Fiesta had two different XR2 engines. Pre- and past-86. Early ones are LUB, hemi, ESC-ignition, Weber 32/34 carb. Later ones are LUD, heart-shaped, distributor without external ECU, Weber 28/32 carb.
There could be something wrong with the "new" engine or you might have forgotten a hose and now have an air leak -> engine running too lean -> cutting out. Also when you think you didn't change anything on the carb's setup... might still need a new setup. Plus moving it around might have damaged a seal or something else.
Won't be a bad idea to take the carb apart, put in a repair kit with new gaskets etc. and give it a proper setup.