Just curious, is there a cylinder head temperature sensor AND a coolant temp sensor on the 03 5.4? I changed out the cylinder head sensor this morning but I also bought a coolant temp sensor (it was advertised as fitting the 2003 F150). I've been having high negative fuel trims and this sensor or sensors, if there are both, are my last resort. Thanks.

 

CHT only. No ECT.

 

Awesome, just wanted to make sure. Thanks!

 

If the CHT was not performing as expected, it should set a fault code.

 

I had read somewhere that if it was starting to fail that it could cause fuel trim problems. That was the only reason I changed it. I'm thinking now it's probably been the fuel pump all this time, I need to check fuel pressure first. There is a whining sound (its louder than before), engine surging at idle, sputtering engine on acceleration, very high negative fuel trims w/terrible mileage, and the truck will accelerate a little bit then sputter until it lowers the trims towards 0. The only "symptoms" it doesn't have yet are hard starting and shutting off/no start. 02 sensors are new, plugs/coils, injectors, cats, all EGR components, intake manifold, pcv valve/lines, all vacuum lines, IAC valve, CHT sensor, fuel filter...I may have forgotten 1 or 2 things but they are all new. It's been a dang cat and mouse game for a while now, but the pump seems like it's probably the culprit now. The MAF and IAT sensor have been cleaned and are reading around where they should so I have ruled them out.

 

A bad pump would cause positive trims, not negative. Check your fuel pressure regulator vacuum hose for liquid fuel. You might have a blown FPR diaphragm.

 

That was one of the things I forgot about, I replaced the FPR last week. It seemed to help the way the engine ran for about a day, but the trims were still negative. If it's not the pump then I'm at a loss at this point.

 

If all the sensors are working, there may be a leaking injector or low compression on one of the cylinders. You can also test the fuel pressure if you want to check the fuel pump performance.

 

It's getting negative LT trims on both banks, bank 2 is the worst of the two though. It does get a P0401 code occasionally too, although everything in the EGR system is brand new...not sure if that has anything to do with the negative trims or not. I chased the P0401 for a while, and even after replacing everything it still comes back sometimes.

 

Might help to tell the story from the very beginning. You started in the middle with the CHT question and negative trims. Has it ever run right for you? If yes, then what happened? Describe the parts you replaced, brand and quality.

Could be wrong injectors, blocked air intake system, or something odd like plugged converters or mufflers. There are diagnostic tricks you can try before replacing parts.

 

I've only had the truck for about 2 years. It ran great when I first got it, then started getting codes for misfires...changed plugs (Autolite) and coils (Edelbrock) and it was good to go. Then, started getting lean codes so on suggestion of a mechanic I changed out the intake manifold (Dorman) and injectors (AA Ignition/they have a lifetime warranty). Next, got codes for both upstream O2 sensors so I went ahead and replaced all 4 (Also AA Ignition) and I changed the fuel filter just because it looked like it had been there for a while. The truck ran awesome for a while after all of that. Then the P0401 code showed up, I found the vac solenoid wad bad as well as the EGR valve being partially stuck. I also went ahead and changed the DPFE/w hoses and the EGR tube. All of those are Standard Motor Products and the hoses are Dorman. I changed the cats out as well just because, and there are only 2 now instead of the 4 from the factory. I don't remember what brand they are though. The IAC valve is new because I kept having a rough idle and my truck would shut off in the middle of the road, it is also Standard Motor Products. I have also replaced several vacuum lines and the PCV valve/lines/fittings, and i installed an oil catch can while I was at it. The most recent was the CHT sensor and it is a Walker Products. Im honestly not sure what to look at next for the surging, rough idle, engine sputtering, and high negative LT trims on both banks.

 

That's a lot. Others have real experience, I just have what I've learned. Your "cleaning" of the MAF sensor catches the eye. You can unplug it and see if there's a change. Apparently the MAF sensor signal is very powerful as far as how the PCM reacts. If you unplug it the PCM will default to a basic fuel-air map. It should run fine, just not as well as with a proper MAF sensor signal. That's a simple quick test of one component.

Your persistent EGR error code might be a clue. Generally exhaust gases are only let through the system at higher RPM since they dilute the fuel-ar mix. You don't want EGR gases at idle.

Finally, aftermarket converters are often mentioned as bad, known to fail rapidly. The second part is a resonator, not actual catalyst bed, but the fact that they left it off implies "cheap".

Just some guesses. The MAF sensor check is quick and easy and won't hurt anything. Might be worth a shot.

 

I will check the MAF again tomorrow, maybe i missed something the last time. Its been several months since i checked it last anyway. The EGR code comes and goes randomly, but on my scanner the "EGR Commanded" looks correct when at idle and in motion, that one has me confused. The cats were just a quick option, hell, maybe they are the problem. I will pull them off and check. The O2 sensors are all fluctuating like they should, but who knows.

 

I'm not saying to check the MAF sensor signal at idle, or check if it's clean. I'm saying unplug it and drive. Just to be clear. Never tried it but I've seen it described as a test, by the pros.

 

Ah, ok, I haven't tried that yet. I will give that a shot tomorrow and see what happens.