I have been racking my brain over this one, at first I thought it was a vacuum leak but could not find any with smoke test. Then after thinking it over I thought that was not right since I am only getting a lean code for one side of the engine. So tried the starter fluid test around the intake manifold with no change to the engine at all while doing this. Need some help on this one, trying to save some money so I do not want to purchase unneeded parts if at all possible. Thanks for the help in advance.

 

Guess I neglected to say, this is on my 2003 F150 5.4 Triton engine

 

What I would check for, vacuum leaks, low fuel pressure, dirty MAF sensor and O2 sensor issues..I would be curious as to what your fuel trims are at.

 

LTFT B1 28.9 %
STFT B1 -2.3%
LTFT B2 -1.6%
ENG RPM 2134
VEH SPEED 29MPH
This is the freeze frame info from when the check engine light came on. way off on Bank 1
Checked for vacuum leaks with smoke test and with spraying starter fluid. Got no results from either. Fuel pressure would cause P0171 and P0174 not just the one to happen and the LTFT and STFT are off only on bank 1
Cleaned the MAF sensor with no change to any readings or ideal

 

I have the same issue on my 2004 Ford F-150 4.6L XLT. I have replaced the o2 sensors, spark plugs, coils, egr valve, clean MAF and fuel injectors. Still have lean code and truck idles rough. Can’t drive over 60mph and I think the truck is in limp mode. Let me know if you figure it out I could sure use the help.

 

Sometimes , if you suspect an intake manifold gasket problem , internally, Remove the PCV valve and plug it so what you do next will not affect intake air.
Then remove the oil fill cap , shoot a short shot of carb/ choke cleaner into oil fill hole. If there is an interal gasket leak idle will pick up the addl fuel from what you sprayed into the oil fill hole.

 

I had that issue with mine except it started in bank 1 now I'm in bank 2 and I've replaced the MAF sensor, PCV valve and tube, bought a new intake, and have checked the wiring for my o2 sensors and it seems that the wiring on the right side burns up and causes a lot things on my truck to act up essentially go into limp mode.

 

have you checked the wiring that runs down the passenger side to the transmission. Make sure it hasn't touched the manifold and burnt up.

 

Rodney, Since the issue is only on one side, I did not see mentioned yet by anyone that clogged or bad fuel injectors could cause a lean issue on one side. Have you checked into this yet? The simplest (and cheapest) thing to try first is to run some fuel injector cleaner through your gas tank.

BTW, does the LTFT number drop as you increase speed or load? This would be an obvious indication that it is likely some type of vacuum leak.