Okay folks, I need help! I have a 2004 F-150 with the 5.4 3V. I started throwing a code for a P0191, P0193, P2196, P2198. I replaced a lot with no solution. Fuel pump, fuel pump driver module, fuel filter, throttle body positioning sensor and the fuel rail pressure sensor. Plus the VVT solenoids, all four oxygen sensors, coil packs, and fuel injectors have been done within the last two years as well. But, it’s losing RPM’s and bucking once it gets to operating temperature. Does anybody have any ideas why it does this? I’m not sure if the bucking had anything to do with the codes. I’m not showing codes since I’ve replaced almost the entire fuel system.

 

The P0191 and P0193 are fuel rail pressure sensor codes.

https://www.obd-codes.com/p0191
https://www.obd-codes.com/p0193

I would also clean the throttle body, get your cats checked for excessive backpressure, and change the spark plugs if they have more than 60k on them.

 

I replaced the Position sensor. The cats have been tested earlier this year. They came back good. I haven’t done a tune up yet though.

 

I see you edited after I posted - looks like you did change the fuel rail pressure sensor. If the 0191/0193 don't come back you can rule that circuit out.

I would still clean the throttle body, watch the video. Be aware of the sticking and breaking issue if you change the spark plugs. If it clatters like a diesel when the rpm drops, you have phaser issues, try heavier oil. You may need a full timing job - chains, phasers, guides, tensioners, and high flow oil pump.

 

No chatter when it drops. I thought about throwing an entire new throttle body at it. For some reason I feel like it’s something extremely stupid that I can’t figure out. The way it runs before it happens doesn’t seem like it’s a major issue. It feels more like an issue of no fuel being delivered into the engine or to much air.

 

First need to ask whether it still has any OBD codes, and if so what they are? If there are no codes, did you determine what caused the P0191 and P0193? Also, if no codes now I'd next check the temperature sensors with a scan tool (that reads live data) since you said