1990 Ford Bronco XLT won't start when engine is warm It will start when the engine is cold but won't once it's warmed up?

Answer 1

This sounds like it is your EGR valve or your IAC sensor ( Idle Air Control Valve). When you car gets hot your EGR valve closes to keep the water flowing so the car will not over heat and relieve excess gas. But when the EGR is bad it will stay open allowing to much fuel and air into the system causing you not to be able to start it when vehicle is warm. The IAC control the regulation of the EGR if this fails it will not send information to the EGR telling it to open or close therefore causing your EGR to stay open and then your vehicle will not fire when hot.

I have no idea. Since your answer hasn't been answered yet, and you may have to wait a long time to GET it answered, I'm going to give you my guesses, and flag it as needing more answers. My comments may give you some useful clues. Metal expands when heated, more so than most other materials. If your car won't start when it is hot, then you have some sort of fuel problem (most likely), OR your engine components are preventing some crucial gadget from moving in a way that it can when it is cold, (tricky, I can't think of what that might be, as your car evidently RUNS when it is hot, just won't start), OR the computer running the diagnostics has pooped out in an unusual fashion, and is thinking that conditions are such that it is SAFER not to start the car. It could also be something really simple, that a real mechanic would be able to instantly be able to figure out. Good luck!