I had been trying to diagnose the issue myself for a while, pulled codes, only got code 33 for EGR Valve Not Closing Properly from my code reader.
The truck would run great until it got warm and then it would start hesitating and would attempt to stall out when I stop and try to accelerate again.
I took it to a shop and they said my fuel pressure is dropping from 32 to 16 PSI under load and reccomended that if I want to repair it myself to start with the in-tank low pressure fuel pump.
They also stated they tested the fuel pressure regulator and it was in proper working order.
Replaced the in-tank fuel pump, ran worse than it did before. It would start sputtering and stalling right after starting it and driving just down the road instead of it warming up and having issues. Put in a brand new high pressure fuel pump and in-line fuel filter (all Motorcraft) and now it's doing what it was before; running strong until it gets half gauge on the temp gauge and then it start sputtering and choking. Any suggestions would be greatly appreciated!

 

Welcome to FTE and the Big Bronco Forum... first lets get some information about your truck. Engine, model year? Obviously we are dealing with a full size Bronco and since you have replaced both pumps I am going to assume we are dealing with a 1989 or older EFI model. (90 and up had a single in-tank high pressure pump). I know it sounds like a no-brainer but have you replaced the fuel filter?

On to your warm-operation stalling. The ECT (Engine Coolant Temperature) sensor can be giving a "false" reading if it "sticks". In other words, the computer won't see a problem with the temp that the sensor is giving because that temp is "within the normal temperature range" that the engine operates. However, if the sensor is stuck at a "cold" temperature and doesn't change, the computer "thinks" that the engine is still cold when in fact it has warmed up. If/when this happens, the computer doesn't trigger a fault code because the engine COULD be that cold... the problem is that even when the engine DOES warm up, the sensor is still telling the computer the engine is cold. On the other hand, if the ECT sensor "sticks" at a warm temperature, the truck will be very hard to start and keep running until the engine has warmed up. The attached .pdf file shows the approximate resistance that you should get from the sensor at various temperatures.

Assuming you get the fuel pressure issue resolved, I'd be willing to bet the ECT sensor is somewhere near the root of your problem with the stalling.

 

Sorry, I filled out the vehicle information in my profile and thought it posted along with the username :P
It's a 1988 Ford Bronco, engine is a 302.
Yeah, when the problem originally started I replaced the fuel filter with a fuel filter from Autozone and when I replaced the high pressure pump I figured just for drill I'd replace it again, and this time it was a Motorcraft filter.

I'm not sure I understand completely (I've read through that several times) what would the sensor being stuck on cold cause it to do? What kind of problems would it exhibit?
Does the ECT directly control the temperature gauge?

As far as the fuel pressure issue goes, I have not had the fuel pressure tested since I replaced the pumps as I don't have the equipment to do so.
I'm beginning to wonder if this could be an injector issue; I have been told that injectors can run fine when the vehicle is "cold" and then act up when it is warm.
I'm also wondering if it could be the oxygen sensor?
The problem seems to be more frequent the more I drive the vehicle and decrease when I let it sit for a while.

Thanks for the info!

 

The ECT (Engine Coolant Temperature) sensor "tells" the computer how warm or cold the engine is. When the engine is "cold" the computer naturally enriches the fuel mixture. When the engine warms up, it leans out the mixture. If the ECT sensor "sticks" at a cold reading, the computer will "think" the engine is cold all the time and keep the fuel mixture too rich causing the stalling issues you have been experiencing.

On the other hand, if the ECT sensor "sticks" at a hot reading, the computer will "think" the engine is warm all the time which won't be bad once the engine has warmed up but getting it started with the fuel mixture so lean, will be a royal PITA.

The reason I mention this as a potential problem is that the computer won't throw a fault code if the ECT sensor "sticks" at a temperature within the range that the computer "expects" to see. The problem only rears its head when the temperature that the sensor is "telling" the computer is NOT the actual temperature of the engine. That's why I posted the chart so you can cross-reference if needs be.

My strongest suggestion is to verify the fuel pressure with the engine fully warmed up. The pressure in the fuel system is constant at 35-40 psi no matter what the engine temperature is.