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I just picked up a 2003 Expedition XLT RWD with a 4.6L SOHC and 163k miles. It is throwing code P0171 Too Lean on Bank 1. The IAC Valve had an internal short to the case, I found a Collapsed PCV Hose and a broken vacuum line and fixed all of those but still have the lean condition and the code keeps coming back. The only noticeable symptom is a little shaking at idle, under load everything seems fine. It has new Upstream O2 Sensors and Catalytic Converters, but the Downstream O2 Sensors look like the original ones so I am going to swap them tomorrow clear the code and see if P0174 comes up instead. Here is my freeze frame data, any help would be greatly appreciated:
Check to makes sure the fuel pressure is up to specs. If it is then you still have a vacuum leak. If you don't find any issues with the hoses it can be the intake manifold gasket.
Isn't this the one with the integrated coolant crossover tube on a plastic intake manifold? They're known to crack and leak where the coolant crossover is
On the 2v 4.6l (or was it the 5.4?) they have the plastic intake manifold with an integrated aluminum coolant crossover tube, which also shares the same gasket as the intake manifold. The plastic gets brittle and cracks near the coolant crossover, voila, vacuum leak, or worse, coolant leak into the intake ports.
Check to makes sure the fuel pressure is up to specs. If it is then you still have a vacuum leak. If you don't find any issues with the hoses it can be the intake manifold gasket.
I am going to test fuel pressure and see, I just ordered a new fuel filter and fuel pressure tester and am just waiting for them in the mail. Do you know what the correct spec is at idle and under load for fuel pressure? I heard it was 55-65 psi. I was also thinking it might be a fuel injector o-ring, so I am going to replace those on Bank 1 and see since it only costs like $4 for all 8 of them.
A few years ago I replaced an Intake Manifold on my 2001.5 Mustang GT with a 4.6L SOHC, it had the plastic/aluminum crossover and started leaking coolant but never threw a code. I put a Dorman one on and it worked fine, came with the Gaskets and everything. Does anyone know if its the same procedure for the Triton 4.6? Thanks for the input.
About 5 days after I did the fuel filter, the light came back on. I ended up replacing the intake manifold gasket, it was blown out at the back of Cylinder 4. While I was in there I noticed the gasket that goes in between the aluminum upper intake manifold, and the plastic lower intake plenum was also leaking so I replaced it as well. While I had the intake manifold out I checked the plugs and they were all Motorcraft and looked pretty new. The gap was good on them so I just re-installed them. I swapped out the O-Rings on the injectors, and found one injector with a broken tip. I swapped that injector out to the other bank a few days ago have not had a code come back yet. Hopefully if the CEL does come back it will be on Bank 2 and then I will know it is the Injector.
I checked the plugs and they were all Motorcraft and looked pretty new. The gap was good on them so I just re-installed them.
While I understand the concept of don't replace what isn't broke...considering how difficult they are to replace I think I would have done so and then taken comfort in knowing they were good for another 100K miles. But that's me. $$
While I understand the concept of don't replace what isn't broke...considering how difficult they are to replace I think I would have done so and then taken comfort in knowing they were good for another 100K miles. But that's me. $$
I have 8 brand new motorcraft plugs for the truck just sitting here in the box, but the plugs that were already in there literally looked brand spanking new otherwise trust me I would have replaced them. I think the last person that had the truck had an extended warranty or something because it looks like someone has just recently thrown a lot of parts at it trying to fix this code. Still no code yet and its been almost 200 miles so it looks like it might actually be fixed finally, fingers crossed, lol...when I did the fuel filter it took about 250 miles for the CEL to come back on though so we will see.
