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Let me give you as much info as I can. I bought a 2003 F350 5.4L 320K miles at a DOT auction about 3 years ago. Ran good. I replaced the coils, plugs and injectors as a tuneup on an old engine. It's quiet and smooth. I had a P0171 and P0174 code pretty much the entire time, but no problems so I've been running it. With the price of gas I figured this is a good time to try to fix the code problems. about 2 weeks ago I cleaned the MAF with MAF cleaner and the throttle body with carb cleaner. Let them sit for about 2-3 hours and replaced to O2 sensors. No change. Prior I noticed my fuel trims long and short terms between Bank 1 and 2 were far apart. My B2O2 was flat at zero. The cleaning and new O2s made no difference for a couple weeks, till Saturday when I left work I got about a mile and the engine bogged down didn't shut off but went from 60mph to 10mph real fast. I pulled over after 20-30 seconds it picked up. I drove another couple miles same thing. I had to pull over 6-7 times in 40 miles to get home. It's sending a p1131 and P1151 code now The radical fuel trims I figured fuel pump and pressure regulator. I replaced those yesterday. My fuel trims between B1&B2 are now almost identical and I'm getting readings on my B2O2. I thought I had it, NO. So with my cheap OBDII I graphed my MAF at idle it reads around 1lb/min but every few seconds it jumps to 36 lb/min and even as high as 45, yet my idle is smooth. I graphed my throttle position its at 19 but it to jumps at idle to as much as 60%, yet I have a smooth idle. I rev it up runs ok but RPMs do fluctuate a little not much then all of a sudden it stalls and struggles to run it will do it if I let it idle too, 1 tiny step from shutting off. 30-45 seconds of this it picks up and runs smooth again. Only when it's struggling to run will I get the P1131 and or P1151. Prior or since I've had no problems with idle, acceleration, or starting. It's only the 30-45 seconds when it bogs out that started Saturday and it bogs out BAD. Any help would be greatly appreciated
EDIT this morning I disconnected the MAF from the harness yet I'm still getting readings with similar spikes. but it did throw a MAF code. I added pics to show how radical readings I'm getting all these are warm engine idle. It idles smooth but to look at these readings you'd think otherwise negative 56? Idle MAF Idle Throttle Position Idle RPM Idle. problem is it's a smooth idle around 725 Intake Air Temp negative 11? it's over 80 outside
Update I replaced the new B1S1O2 with the old one and my stalling seems to have ended. but now it's kicking out the P0171-P0174 codes again. Ohh well it's running. Funny that was the only sensor that seemed to be reading good. I'll let yall know more tomorrow after I put about 80 miles on it
Last edited by aquadave; May 3, 2022 at 05:17 PM.
Reason: Update
Why replace the fuel pump if the fuel trims between banks were different? Fuel delivery would affect both banks. Have you checked for vacuum leaks on the perpetrating bank?
Why replace the fuel pump if the fuel trims between banks were different? Fuel delivery would affect both banks. Have you checked for vacuum leaks on the perpetrating bank?
— Dave
It's old and that was last on the list for P0171 P0174 and it did make a difference bringing my trims together
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