Unfortunately checking check engine codes won’t help you any. All that computer tells you is whether or not the circuits are plugged in. I had similar problems as you. Truck wouldn’t even stay running. I replaced crank sensor, when I pulled it out, I saw it was split down the middle. Replaced with new aftermarket, problem fixed instantly. A month later, I would get back fire under acceleration only while engine was cold. Again, only codes was 12 and 55. I replaced coolant temp sensor for computer problem fixed. While I had coolant temp unplugged I turned key on to see if it would even throw a code. Sure enough got a coolant temp sensor code. So yeah, checking codes don’t do squat if any sensor is bad. As long as it’s plugged in, computer won’t tell you anything.

 

I,m going to O'Rielys to loaner tool -fuel pressure tester

 

Well got the tester for fuel pressure. Reads about 30 psi while on, when engine running it fluctuates between 40 psi & 35psi, fluctuates constancely not steady-bad fuel pump?

 

Cycle the key a couple times, to thoroughly prime the system, (don't start the engine) what does it read?

 

stays at 30 psi

 

But it goes up when it's running???

 

yes-close to 40 psi while fluctuating

 

Hhhmmm..... That *should* be ok... though it's low when not running.....