I need help with a problem. I am working on a 2003 F150 4.6L with 199K miles for a friend. I do not have SES light, however I am getting a pending P0171 code. I've been working on this for the last 7 days and can't figure it out. Here is what I have done. I did a smoke test and found one small vacuum hose with a tear. I replaced that hose. I also observed a small amount of smoke coming from the EGR valve. I did a vacuum test on the valve and it holds 6lbs of vacuum. No other smoke was observed. I have cleared the codes and completed a drive cycle test. The pending P0171 appears again. I have replaced the O2 sensor before the CAT. I did a resistance test on all injectors on that bank. I also checked for normal injector sound using a stethoscope. I have pulled the spark plugs and done a compression test. All cylinders on both banks are normal for this amount of miles. I had a intermittent misfire on cylinder #2 and I replaced the COP on that cylinder. I have monitored the live data over a 50 mile drive test. The short term fuel trim on the #1 bank appears normal. However, the long term fuel trim stays around 18-20% enrichment. Any help/ideas would be appreciated.

 

Something you should be aware of; a smoke test will not always show with an intake manifold gasket leak.
Have you tried switching the plug from #2 spot with another plug from THE OTHER BANK.
Have you considered cleaning the MAF sensor, checking for worn bushings on the IMRC shaft?
Do you have Freeze Frame capability so you can see the PIDS at the time the code is set?