Hey everyone I'm a new member. And I'm having an issue with code P0171 system too lean bank 1 on my 2004 GT. This code has been coming on and off by itself for 6-8 months now. I know it's the passengers side. I recently changed the intake manifold because it was leaking at the heater core. I also changed all these parts to freshen up the engine. Need help on what else to do thanks!
PCV Valve
Camshaft positioning sensor
Crankshaft positioning sensor
idle air valve control
Throttle body positioning sensor
Throttle body gasket
Intake manifold gasket
MAF
PCV to upper intake vacuum hose
Exhaust Gas Recirculation Pressure Feedback Sensor
Front o2 sensors
Fuel injectors
CAI filter

 

You've done the stuff that most guys throw at this code. It is usually a vacuum leak. Take a good can of Berryman's B12 and lightly spray around the intake plenum and where the TB mounts and all the hoses. It is usually a very simple cure for this and P0174. If you go out the 1997-2003 section on F150 Forums, type in those codes and you'll find a 1000 answers. It is very common for 1997-2004 Fords with 4.6 throwing this code. Hope this gives you a start and end to your problem. Good luck.

http://www.f150forum.com/search.php?searchid=10752937

 

Ok I'll try that it's been driving me nuts.. And I have a vacuum gauge on my gauge pod and it reads normal.. But do I hear a noise coming from the passengers side by the heater core hose

 

Gonna sound nuts, but try changing the alternator. I had a problem years ago that we just could not solve, and I changed a list as long as yours. Apparently the alt was sending bad electrical signals through the system and causing everything to go haywire.

 

I'll have the alternator checked out. It was replaced about 6 months ago and I had the code before that. But I'm willing and open to all suggestions.

 

Good thing about the mod motors is that they're not quite as computer based as the newer 4.6's and 5.0's. They're relatively easy to diagnose.

 

That is true.. But I'm having the hardest time finding the vacuum lines or I'm blind. For some reason finding a diagram online seems impossible also lol

 

If you have access to a 2000=04 Mustang service manual, go to section 140-1 and it is the picture of the vacuum schematic for your year. It is very similar to the 04 Crown Vic PI schematic. That one is shown here. I hope it helps you out some. I don't have a SN95 manaul, but you can download that here. http://www.mediafire.com/download/ao...ual+backup.pdf

 

Thank you! That manual is awesome!

 

So I took the car in to be leak tested with the smoke machine. NOTHING.. Lol car is solid with no leaks on the vacuum lines. They did notice some some leaking out of where the CAI housing meets the MAF meter. They said that was the cause. So I siliconed everything. Your guys thoughts on that?

 

As long as you use sensor safe silicone, why not. If you don't have that kind of silicone, I'd say stay away from it. Permatex #6 (BR) is not safe. Just so you know. Most of the others are ok. 598 (BR) is good to use but the #6 stuff really messes with sensors and screws things up badly.

 

Thanks so I did the silicone thing and I also changed the fuel rail pressure sensor. Still getting the same thing. Do you think it could be the CAI? Mine sits inside the fender well. Should I try one that sits inside the engine bay?

 

Or last but not least change the fuel pump? I hate seeing the CEL