Issues with 2005 Rumble Bee - codes P0171 & P1074 and falls on it's face at WOT

[ClayC]

2005 Dodge Ram 1500 w 5.7 and 36K miles.

My dad bought this truck in 2012 and it pretty much got parked in a garage for years with a 1/2 tank of fuel. Got it out the end of March and got it home. I almost immediatley had a misfire code on cylinder 5. Filled up gas tank and drove it for a few days but code never went away.

Swapped cylinder 1 and 5 coil, problem persisted.
Swapped cylinder 1 and 5 injector, problem moved to cylinder 1.
Replaced injector and no more misfire code.

Drove it for a couple of days with no issues. Then one day when leaving work I started it and it died. Started back up and died again. It was acting like it had couldn't hold the idle, but it did finally go and drove home. I can start it and drive it if needed, but it will occasionally die at start up the first time. At part throttle it drives fine, plenty of pick up. At WOT it falls on it's face. RPMs will increase (not like normal but they will increase) but it wont' "go" anywhere. Back to part throttle and it's fine.

I have 2 codes -

P0171 - System Too Lean Bank 1
P0174 - Fuel System 2/1 lean

I've checked for vacuum leaks and haven't found anything. I've monitors the O2 sensors while driving and don't really see anything that sticks out to me.

I'm thinking about replacing more injectors because of the issue I had right at the beginning and I'm thinking I could have some of them gummed up.

Anyone have any thoughts on what it might be or things to look for?

thanks!!
Clay

 

[LoneWolf3574]

These are possible causes for those codes and I am aware that you have already checked & replaced an injector.

There could be a vacuum leak downstream of the MAP sensor (ie intake gasket leak)
Possible cracked vacuum or PCV line/connection Faulty or stuck open PCV valve
Failed or faulty oxygen sensor
Sticking/plugged or failed fuel injector
Low fuel pressure
Exhaust leak between engine and first oxygen sensor (usually broken exhaust manifold bolts/studs)

Read more at: https://www.obd-codes.com/p0171 and https://www.obd-codes.com/p0174
Copyright OBD-Codes.com

 

[jws123]

I would check the fuel pressure you said its been sitting that alone can kill a fuel pump.

 

[ClayC]

I ended up replacing the injectors and that didn't fix the issue, so then I replaced the fuel pump and the upstream O2 sensors. I didn't really suspect the O2 sensors but I figured it wouldn't hurt. I think the main issue was the fuel pump. When I pulled it out the suction strainer on the pump had started to disinegrate, and when I touched it then it completely fell apart. I think that was limiting fuel volume.

Truck drives great now but I still have an issue. I think the new fuel pump check valve is bad because it won't hold fuel pressure when it's off. It slowly looses pressure and within an hour it's below 20 PSIG. I checked the injectors and didn't see any of them leaking when there was pressure on the system.