Hey my 88 bronco has an 89 5.0HO in it from a stang it's giving me a lot of backfiring at low rpms both warm and cold no clue what to start looking at. Could it be a fuel problem? Pleas help !!!

 

Check the fuel pressure, run the KOEO tests and stored code display. List any codes by number and when they were displayed.

Fuel pressure should be ~32-35 PSI at idle. Remove the vacuum line from the fuel pressure regulator then the pressure should go to ~40-45 PSI. Put the vacuum line back on, then blip the throttle. The fuel pressure should rise again to ~40-45 PSI.

 

ok so after I test that what will it tell me. That the regulator is bad or just that there could be a problem further down the fuel line ie pump or filter or heigh pressure pump

 

Verifying the fuel pressure will narrow down the cause of your issue.

If it's good start looking at vacuum leaks and spark quality.

If the pressure is out of spec. the first thing I would replace is the fuel filter, then the pressure regulator. If it's still low you most likely have a bad pump.