I have a 2000 f150 with 5.4 Triton with 165k miles. I did invest in a code reader. It started missing and code P0302 came up along with P0171. Put new coil on #2 and truck ran fine for a few days. Then it started to run rough again. Shaking, Idle rough, no power and CEL came on again. This time code P0171. I changed out fuel filter to no avail. My next step was to start looking for vacuum leaks. As I'm searching these forums (so thankful that they exist) All I am finding is trucks with this problem also get P0174 code. My question is since I am only getting lean on one bank does that pretty much eliminate things like MAF or the famous elbow vacuum leak and make something that only affects one bank like an O2 sensor on CAT more likely? I'm just enough of a mechanic to get myself in trouble so any details I can get would be very helpful. Thanks in advance...

 

at 15 years old and 165 K miles I would definitely consider the vacuum hoses. The get hard, crack, burnt edges, ect..... It is common to get the 174 code also as you said, but not a necessity...... One good spot for bad hoses is the EGR above the drivers side valve cover more toward the back half. There are two small hoses, maybe 1/4 inch ID and 3/16 inch ID and each is about 8 - 10 inches long. Pull both off and see how brittle they are / cracks that might leak air. Some get hard from being close to the exhaust manifold tubing and you can have burnt ends....

Consider pulling other hoses off one at a time and examine each for hard / crack / broken.......... After you eliminate all vacuum problems, then worry about other causes.

 

Your truck may be just a smidgeon away from also throwing the P0174. With your new scanner, look at the Bank1 and Bank2 STFT (Short Term Fuel Trim) and LTFT (Long Term Fuel Trim). When the sum of the fuel trims for each bank exceed about +28% the PCM will set the P0171 for bank1 and P0174 for bank2