My 1990 Ford XLT Lariat with the 5.0 302 recently started stalling out randomly. You all are much smarter than me, so please help me diagnose why, here are the facts:
- Randomly stalls, sometimes a few minutes after I start up, sometimes not at all, sometimes after 10 minutes of highway driving
- Spark plugs - I pulled them recently to inspect them, they were covered in a little bit of white residue which could mean that the engine is running lean, but it also could be from fuel additives that I put into the tank
- After about 15 minutes of driving, a check engine light comes on
- Runs completely fine besides this

I recently got done doing a lot of work to the truck, here are some things that might be involved - New ECU, New IAC, complete smog delete which entailed EGR delete, removal/plugging of vacuum lines to the EGR TAB TAD solenoids and then removing them and placing 75ohm resistors in their plugs, carbon can removal and cutting of the evap lines, now the evap line is just venting open air, and plugging all the lines that go into the engine, taking off the parts that go into the engine and then plugging them. I have done a lot of other work to it, but I don't think it would cause this issue.
I recently checked for vacuum leaks and I couldn't find any, but I might have missed them as I was using a crappy homemade smoke machine.
I am thinking it has to do with my fuel system, maybe the FPR or bad fuel pumps, maybe a clogged filter... not really sure. I tried to test fuel pressure from a schrader valve on the fuel rail but I don't really have the proper tools for it, I do know that after the initial turning of the key and the pressurization of the fuel lines, pressure slowly decreases after that initial pressure up. Both of my fuel pumps are loud also whenever they are on. Please help me!