Tommy J

2004 FX4 126k. I've been dealing with these 2 issues lately. Lean codes and bogging down. Don't know if the 2 are related but the bogging down and falling flat on its face are driving me nuts. The symptoms are varied. Sometimes it does it when pulling out with a lot of peddle and other times while moving and going to accelerate it hits a flat spot around 2000rpms but always seems to slowly come back up to speed when I stay on the gas. I put a dorman FPDM in about 3 yrs ago and was wondering if that could be something I should consider looking at. The truck starts fine otherwise. All filters were recently replaced, foam around air box etc

F150Torqued

@Tommy J

It could...

Laws of Hydrodynamics dictates that the amount of fuel delivered thru an injector while inergized for a specific period of time - is directly perportional to the fuel pressure "ACROSS" the injector.

The FRP Sensor senses fuel rail pressure (relative to intake vacuum, ie: ACROSS the injectors), and provides positive closed loop feedback signal to PCM so it can adjust fuel pressure via the FPDM. The FDPM provides % duty cycle square wave voltage to the actual fuel pump inside the fuel tank - causing IT to modulate the fuel fuel pump output - through fuel filter - into the fuel rail.

THUS - if anything in that closed loop system is 'out of wack' - it could proportionally degrade fuel delivery 'THRU' the injectors, and cause the PCM to lengthen STFT trying to correct / compensate for it. Bogging could be the result of lack of fuel (energy). LEAN codes occur strictly because LTFT+STFT fuel trims are being lengthened more than 30% to compensate for oxygen (lack of fuel ratio) in the exhaust.

So, I would say the FPDM 'COULD' cause fuel delivery deficiency and thus 'bogging down' AND lean codes.

Monitor Fuel Trims, Fuel Pump Duty Cycle, Fuel Rail Pressure.

To diagnose things, I like to challenge certain sensors to determine what happens an if they are functioning as designed. /// While monitoring STFT and Fuel Rail Pressure - remove vacuum line to the FRP sensor and plug it. Connect a short piece of vacuum line to the FRP sensor itself and _suck_ (and _Blow_) on it.--- Observe STFT and Fuel Rail Pressure ///

redfishtd

really good tool to see if thats whats happening .I have had the dorman fpdm for years ,it seems to have a good reputation .However the gasket in the connector to it caused me grief by causing intermittent connection but I finally pulled rubber gasket out and that was years ago . Never resealed it, been thru more than a few floods from hurricanes ..

Tommy J

So, Only one code popped up earlier this week and it was 0174 which is bank 2 lean. I used to get a single bank lean and the other pending until I regularly got both banks lean. My LTFT were around 12 to 14 at idle and would go up with throttle while parked. STFT would fluctuate in the single digits My freeze frame showed long terms in the 20's when it threw a code. So, last night when I was poking around the engine I noticed my oil fill neck where it meets the valve cover looked a little ugly. I remembered that on more than one occasion when I changed the oil the neck spun loose with the cap so I siliconed it a while back. It looked like there were some slight gaps so I removed the neck or spout or whatever its called and noticed the o ring was chewed up in one area. I cleaned it up and re installed and applied silicone again all around the base till I get a new o ring. Did'nt drive far today but no codes and LTFT were in the single digits while idling and went up with increased throttle. Could that have been it??? the cause of my lean codes. Don't know yet if it still bogs down or not. I"ll be taking it on the highway this weekend. Im crossing my fingers it might have been something that stupid that I might have overlooked.