SupermanZ28

I've got a 95 z28 and I'm having some problems with my build. I've got a 383 stroker; did a mail order tune from Harris Performance. It's been acting funny for a while, but I just assumed that it was bc I needed to get it dynoed tuned. I do have tuner cat, but I haven't used it yet. Before it messed up, car ran and idled fine, just ran a little rich.
So for my problem... Used to do highway pulls and stuff (esp when running late to work) Put the car in 4th and open it up... Hit about 120 and shift into 6th to cruise, right when I shift, car cuts off. I either have to drop it into 5th or back to 4th to jump it back off, it jerks and then cuts back on. Did this for like a week or two up until about a week and a half ago. Left a traffic light and shifted into 2nd at about 3k rpms, pressed on the gas and car started backfiring, got scared and shifted into 3rd. Backfiring stopped until I pressed on the gas again and it backfiring, immediately shifted into 4th, and it stopped again. Cruised in 4th at like 25mph until it started slowing down, shifted back down into 2nd and it starting backfiring again, so I pulled over and cut the car off. Did a visual check and nothing looked wrong, went to start it and nothing happened. I thought it was my fuel pump bc my injectors were basically maxing it out the stock one, so I installed a granatelli 255.
Tried to crank it up and it won't fire. I know I have fuel pumping from the pump, I've got spark, I've got compression, and I've got air. Motor will crank, but won't fire up. If you turn the key back and keep your foot on the clutch, you can hear the motor slow down and intake backfire (very quiet boom, boom). I have no idea what is going on, my only thought now would be my pcm. Please help, want my baby back on the road.

Brian68

Not trying to be an ***, but did you replace the fuel filter? I wouldn't worry about the PCM yet, sounds like low fuel pressure.

SupermanZ28

That's what I was hoping for, but I changed the fuel filter when I changed fuel pump. AC Delco filter and Granatelli 255lph pump.

Brian68

There is still a regulator failure to look for with a fuel rail pressure check.

"Motor will crank, but won't fire up."
Will it fire on carb cleaner in the intake?

SupermanZ28

Don't know if it helps, but it would also cut off when I try to reverse. That's the main reason I was thinking loss of fuel pressure, but if it was fuel pressure, changing the pump would have fixed the problem. No problems 1-4th pulls up to redline, but when I get out of it by shifting to 6th or neutral and try to cruise, the car cuts off.

SupermanZ28

Didn't have access to a pressure tester, gonna try to borrow one tomorrow. Pressed on the hookup and it shoots out fuel.

Brian68

Could be PCM grounds or resistance in power circuits. I would still want to know rail pressure. O2S going rich?
How did the cap/rotor look?

SupermanZ28

How would I test the PCM grounds? Haven't touched any of the wires since I got the car, just unplugged 4 plugs, sent it to get tuned and plugged them back in. All I have to do is plug the tester in and prime the fuel pump right? Not really a good thing, but I know I'm running rich bc I've burned my cat out. I know i need a real tune, but I keep breaking random stuff right when i get the money for the tune.