I have a 04 Lariat 5.4 215,000 miles and it has been running horrible. I fired up my torque app and got these codes. p0171, p0174, p0300, p0351. About 65,000 miles ago i had all plugs and cop's changed.

At 2000 rpm exactly in any gear she starts bucking and shaking pretty badly. I had to get on the interstate the other night and it wouldn't move. Semi was kind enough to show me how close he can get without hitting me. The p0171 and 174 seem to be a elbow the gets torn. I bought the elbow and i cant for the life of me find it behind the intake. Where around do i stick my hand? Drivers side or passenger side etc.? I sprayed a can of carb cleaner around the back of the intake and couldn't hear any change.


The o2's have never been changed so i should probably add to the list i would just like to get the two p0171, and p0174 and change that elbow since I have it. Then I'll work on my cop's since I have a couple extras.

 

If you have been running with the lean codes for a long time you may have cooked the cats. If it feels like it has a cork up its butt at about that rpm range, that is classic clogged cats symptom. I hope it isn't.

The elbow should be dead center right in front of the fire wall on the back of the intake.

 

There is no elbow behind the intake on a 5.4 3 valve. Look for your vacuum leak elsewhere.

With 65k on the plugs, it's time to change them again.

 

@glc,


There ACTUALLY are TWO (2) elbows "behind" the intake on the '04 5.4l 3v. One is a 'flimzy' soft rubber thingy that provides vacuum to the 'vacuum' compensated fuel rail pressure sensor - and it is definately a source of problem for vacuum leaks. It originates at a port on the rear passenger side of the IM at the very bottom of the belly, and there is NO WAY to see it or reach it without removing the IM !!!


The other provides vacuum to the power brake booster and the 'elbow' is stablized with a metal bracket bolted to the rear of bank 2 head. There is NO WAY to connect or disconnect it without removing the IM. (As it so happens, mine was only half connected from the factory and a source of a minor leak).


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@energizedsbs


I finally found the link I wanted to provide that will definitely help you.


http://www.ford-trucks.com/forums/10...ml#post9929436


Also, after trying for about 4 hours to reconnect the elbow to the break booster - I finally just connected a 3 foot section of new vacuum line to the port on the IM, and THEN installed the damn thing and killed the factory connection.

 

Sorry I wasn't more specific - there's no PCV elbow on a 5.4 3v. My fault.

 

@energizedsbs


I notice you mention using the Torque App. I have been through identical symptoms with codes P0171 and P0174 and same repair efforts. LIKEWISE, I could not hear a noticeable change in idle spraying (I used ether) around the IM. But I could DEFINATELY see it on Torque graphs of O2 sensors and Short Term Fuel Trims very dramatically. Since you use Torque, you might try setting up a dashboard screen like I did and monitor these items while spraying carb cleaner or ether. I could tell I either had leak in manifold gasket or cracked manifold on bank 1 / around cyl 2-4. Replaced IM, as well as driver's side rear.


Also. I am a firm believer O2s should be replaced > 100,000. They get lazy & tired (coated with exhaust contaminants) and their calibration drifts - in the direction that causes increase in fuel trims and deteriorating fuel mileage.


As for COPs. I differ with everybody on this one. There is not a damn thing in a COP that wears or deteriorates with either use or age - provided it is clean / dry / and has no mechanical cracks. They are prone to getting cracked at the weakest point where the wire plugs on to top - from us leaning on them while working under the hood. But other than that, they have NOTHING in them except two coils of copper wire and an iorn core. Boots, however are another story. Replace them and clean / streach the spring wires that go to the plugs and use dielectric grease. If you have doubts about one, you can test it with a coil testor from Amazon for a fraction of the cost of a single COP. See the Ampro testor for $11.00 here:


Also, I would assume you have ran across my 'off the wall' theory about misfire problems in this post:
https://www.f150online.com/forums/v8...ml#post5159499


Good luck. Hope this helps.

 

You can buy boots that also come with springs as a kit. Fraction of the price of a whole COP.