96-00 454 Running Rough

[scons96]

UPDATE: I replaced the fuel pressure regulator yesterday and the fuel trims seem to be much better. Bank 2 is about the same as it was before, but bank 1 is down to around +13% at idle from being at +30% and higher. HOWEVER, the truck still runs incredibly rough. I had to take the distributor cap off anyway to get at the FPR so I checked out the rotor as well and that all seems to be fine. The only thing that seems to be different besides the scan tool data is now when I put it in gear it doesn't die, whereas before I had to put it in neutral at stop and go lights so it wouldn't shut off. So it seems I did fix something at least? I'm still pretty stumped though. Gonna do some more digging.

 

[Christian Steffen]

UPDATE: I replaced the fuel pressure regulator yesterday and the fuel trims seem to be much better. Bank 2 is about the same as it was before, but bank 1 is down to around +13% at idle from being at +30% and higher. HOWEVER, the truck still runs incredibly rough. I had to take the distributor cap off anyway to get at the FPR so I checked out the rotor as well and that all seems to be fine. The only thing that seems to be different besides the scan tool data is now when I put it in gear it doesn't die, whereas before I had to put it in neutral at stop and go lights so it wouldn't shut off. So it seems I did fix something at least? I'm still pretty stumped though. Gonna do some more digging.

Just for the hell of covering all your bases you might want to check the key on engine off fuel pressure. After that I'd start looking for a spark issue. Do you have a scan tool that can shut off injectors? If you could kill on cylinder at a time that would help.

 

[scons96]

Alrighty well I feel like a bit of a clown haha. Turns out I had the spark plug wires mixed up on bank 1 so the truck was essentially running on 5 cylinders. BUT, all the work I did was not in vain because I did confirm the FPR was bad. I knew it had to be something that I did because it ran fine beforehand. Thanks everyone for the advice.