VinnieB

My 99 F-150 4.6L has an ongoing issue the both lean codes. Pretty much everthing has been changed which influences
these codes yet upon analysis lean codes are in the correct range yet the check engine light comes on. So far all the valves and sensors
are new as is the fuel pump and the intake manifold is new. Any insights?

BareBonesXL

Post the actual code numbers, and freeze frame data or live data if you have it. "Codes in the correct range" doesn't really mean anything. Lean conditions are indicated by fuel trims. The two common codes are P0171 and P0174.

Johnny Paycheck

All those new sensors and valves are working (the old ones likely were as well) and the computer is telling you something is rotten.

Getting to play with our company truck with a 4.6 in it, reach behind the intake and slam your face up against the rear reaches by the cowel and feel for a collapsed hose. I believe it runs up to the passenger side valve cover. That hose is pretty flimsy and rips at the bend.

VinnieB

Sorry BareBones the fuel trims are in the correct range and shouldn't generate the error codes. Mechanic also changed the ECU
in case that was faulty

BareBonesXL

Not really sure what that would mean. The PCM uses the trims to generate the code. The logic chain is busted. Your story makes no sense.

Did you actually see the codes or did the mechanic just tell you he saw them? Might be worthwhile to stop by an auto parts store and have them read. Get the code numbers, not somebody's description of what they mean.

VinnieB

Just got the data from the mechanic at the point where the computer generated the fault codes 171 and 174 at operating temperature Bank 1 Short Term = 6 Long Term = 3
Bank 2 Short term = 5.5 Long Term = 6.3 According to him wilhin 10% is in tolerence and no code should be generated
Parts replaced to date Fuel tank, fuel pump, fuel regulator, MAP, MAFS,DPFE sensor, evap control module, Disasembled and replaced uper and lower intake gaskets checked for
unmetered air leaks none found.

Any suggestions before it goes to the dealer?
1999 1-150 base model 4.2L no A/C

99F150V6

P0171 - System to Lean (Bank 1) The Adaptive Fuel Strategy continuously monitors fuel delivery hardware. The test fails when the adaptive fuel tables reach a rich calibrated limit.

For lean and rich DTCs:

Fuel system
-Excessive fuel pressure.
-Leaking/contaminated fuel injectors.
-Leaking fuel pressure regulator.
-Low fuel pressure or running out of fuel.
-Vapor recovery system.

Induction system:
-Air leaks after the MAF.
-Vacuum Leaks.
-PCV system.
-Improperly seated engine oil dipstick.

EGR system:
-Leaking gasket.
-Stuck EGR valve.
-Leaking diaphragm or EVR.

Base Engine:
-Oil overfill.
-Cam timing.
-Cylinder compression.
-Exhaust leaks before or near the HO2Ss.

Same goes for P0174

dontherogue

Vinnie, I had similar problems on my '99 XL 4.2. I got codes P0171, P0174, P1131, P0133, and P1132. The first thing I found was a hole in a rubber elbow located in the line that starts with the pcv valve on the passenger side valve cover near the firewall, and then re-enters the intake just under the throttle body. The elbow is accessible after you remove the throttle body cover and housing from the air filter system. I described this in more detail in a thread "1999 4.2l pcv system driving me nuts" on this forum back on 05-09-2017.

The new elbow resolved P0171 and P0174, but not the other codes. I had to replace the two upstream 02 sensors to get rid of the remaining codes. The 02 sensors were replaced in May 2018, and I have had no codes since. I'm not saying your problem is identical to mine, but my truck is also a '99 with the 4.2 liter V6. Best of luck.

Jbrew

No ECU with these trucks, the PCM controls it all.

As said above, it's usually the PCV elbow w/both banks lean. This very one in fact, -

Jbrew

No MAP sensor as well.