Lean on both banks?
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Joined: Mar 2009
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Lean on both banks?
This is on an 03 4x4 5.4 It is showing lean codes for both banks. The truck has 185k miles on it. I'm going to start with a fuel filter because I dont think it has ever been changed. Hopefully that will fix it but, my luck is never that good so i'm already wondering what else it could be. Do bad 02s read lean when they go bad? It runs fine. I know it could be a number of things but what is most common on this truck for this problem?
Also the wipers dont work right. They stop at random and wont move unless I mess with the switch. It does it on every speed. I'm guessing it just needs a switch?
Thanks Mike
Also the wipers dont work right. They stop at random and wont move unless I mess with the switch. It does it on every speed. I'm guessing it just needs a switch?
Thanks Mike
Former ******
Joined: Nov 2004
Posts: 4,901
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From: Salt Lake City, Utah
A bad fuel pump can also cause lean, but the pump can be tested. Vacuum leaks are a common problem and can cause a lean condition. MAFs usually err on the lean side when they get dirty. O2 sensors loose signal strength over time, and the computer will interpret it as lean. However, lean codes are set when the computer errors out on an extreme and the engine is still lean when the correction still doesn't work. It is a good idea to replace the sensors if they have over 80K on them, but vacuum leak is a more than likely suspect.
Hotshot
Joined: Jul 2005
Posts: 11,932
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i agree with Bear. start by pulling each small black rubber vacuum line and connector off one at a time and see if it is hard, cracked, or loose on the fitting. I had that on a F150, lean codes due to bad vacuum hoses. hard and cracked due to age. heat.
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Joined: Dec 2004
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This is the front elbow the back elbow is worse but on the inside and could not tell till it was off. 
Last edited by 80f100302; Jul 19, 2009 at 11:26 PM. Reason: trying to add picture
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