96 F150 351 Throwing Codes?

[NeXtras]

Whats up guys..

buddy of mine has a 96 F150 with the 351 in it, MAF.. He's throwing two codes, P171 and P174, both system too lean codes ive been told..

He's replaced all three o2 sensors, did plugs, replaced EGR Valve and EGR tube, PCV valve, MAF Sensor.. did quite a bit of work and he still has the codes. He did have them cleared but they came back..

any ideas?

 

[blacksnapon]

Time to start looking for vacuum leaks. Most generally they show up on the intake. Another possibility is the vacuum hose to the booster and the grommet in the booster.

 

[NeXtras]

Time to start looking for vacuum leaks. Most generally they show up on the intake. Another possibility is the vacuum hose to the booster and the grommet in the booster.

The dealer told him they tested for Vac leaks with smoke and didnt find any

 

[Black150]

How's the fuel pressure? Not many things to cause a lean mixture.

 

[conanski]

Leaks in the air injection system.

 

[95F350XL]

Alotta fords with MAF get the lean code when the MAF is dirty, tell him to gently blow the sensor out. If not he will need a new MAF.

 

[NeXtras]

brand new egr and injection tube.. NEW MAF as well

 

[conanski]

Another thread I was reading says one of the leading causes of P0171/P0174 codes is the DPFE sensor, it can go bad and not throw a specific DPFE code and this causes the EGR valve to open more than it should and that will result in a too lean condition.