I have a 00 lightning with 41k on it my ses light and setting codes p0171 & p0174. I have replaced the pcv vales and the 90 degree elbow on the back of the intake. I cant find any vacuum leaks. there is a K&n air filter on the truck and i noticed that someone (not me) made a hole for the air temp sensor and used a cheep o ring to seal it i did replace it. does anybody have any other clues what could set this code?? the only other change to the truck is it has a fuel cell. Thanks for all your help.

 

Search the forum for those codes. There have been several posts on this topic.

 

Ok thanks subskip. I will do that again but let me ask you this I just notice I have a air breather where my oil cap should be. Do you think that could cause the p0171 codes??

 

Yes it can. I have even heard of a bad rocker cover gasket causing lean codes.

Try capping off the breather and clearing the codes.

 

ok i will try that. Do you know if all the ford trucks use the same oil cap or does the lightning have a different cap of its own?? Thanks Jgger.

 

any of the 4.6 or 5.4 F-150's will have the same cap...

 

Ok thank you Tarajerame and just to let you know i put a stock cap back on and i got my hands on a scan tool. I found my Long term fuel trim is at 25% on both banks. Short term fuel trim is bouncing around -3.9 to +4.6. I did notice that O2 sensors vdc on bank 2 sensor 2 is at .14vdo ad bank 1 sensor 2 is bouncing around .08 to .14. do you guys think i have an issue with 02 sensor on bank 1 sensor 2?? By the way i did clear the codes and I'm driving it to reset the readiness monitors. Do you guys think i should replace the K&n filter with a stock one?? I don't have any of the stock parts but these codes are driving me crazy. thanks so much for all the help.

 

Just an update I replace the air breather Cap with a stock cap and cleared the codes. After a day of driving the lean codes came back. My long trek furl trim did go down to 14%. I also stared to cap of anything that uses vacuums power. Fuel trim stayed around 10%. I'm going to try to test the fuel pressure next. If anyone has anymore hints let me know. Thanks so much for your input.

 

stil have the palstic Y in the fue tank?? if so it might be cracked

 

Tarajerame I'm not sure. Do you have any pictures of it??? My truck has a fuel cell in it. Thanks

 

Ok time for an update. I found my fuel pressure is at 29 psi engine running. Factory specs is 28-50 psi. I've seen other post stating that weak fuel pressure can cause lean codes. do you guys think that the lean codes are due to my truck having a weak fuel pump?? Thanks

 

Got any pics of the fuel cell setup?

 

No i don't slammediam but im going to make a new fuel cell with my lil bro. Who ever made used this fuel cell did a crapy job. No spot for the FTP sensor and they just cut a hole in the top and stuffed the pumps in there. I took a look at the fuel pumps to see if both pumps where installed and i found all type of junk in my fuel cell. I'm hopping the week fuel pressure is causing my P0171 & P0174. Has anybody had a weak fuel pump cause these codes?? I have check everything from vacuum leaks to checking all sensors. the only thing left is the fuel pump and it needs to be replace no matter what. so im keeping my fingers crossed. if this doesn't fix it then its going to a ford tech and ill let everybody know what the problem was. Thanks for the input.

 

Just an update i finally finish my fuel cell and installed 2 wallbro 255's. My fuel pressure is still vey weak so i checked the voltage on my fuel circuit and voltage is at 12v at prime then it goes down to around 3-4v. so I checked my fuel pump resistor and it ohms out at 1.2 ohms. so I've been on this site all day to see what upgrades my lightning brothers were doing and i like the 2 resistors set up with the heat sink. So i bought 2 heat sinks for a few dollars and I'm going to order the fuel pump resistor tonight. My big question is does the dual resistor provide a full 12v to the walbros?? i don't want to do the full fuel system upgrade or jumper the hi low relay but i don't want to shorten the life of the expensive fuel pumps. Another question i have is what is the resistor ohm out at??