Running Lean, any suggestions??
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Junior User
Joined: Jul 2004
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Running Lean, any suggestions??
The other day my SES light came on, truck still ran fine but i went adn got the codes read today. PO171 and PO174 bank 1 and bank 2 system too lean.
The truck is a 99 F-150 w/5.4L. They suggested that I clean the MAF sensor. I cleaned it but was wondering if it could be anything else. Thanks for the help.
The truck is a 99 F-150 w/5.4L. They suggested that I clean the MAF sensor. I cleaned it but was wondering if it could be anything else. Thanks for the help.
Senior User
Joined: Sep 2003
Posts: 223
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From: York, PA
Low fuel pressure from the fuel pump, clogged interiors of the fuel injectors in the nylon socks, plugged fuel filter, low pressure calibration on the fuel pressure regulator.
Exhaust manifolds leaking, Large intake vacuum leak, PCV hose broken, intake manifold broken or gasket leaking, plenum gasket leaking, power booster leaking vacuum, Idle Air Control motor sticking open.
Mass Air Flow issues usually bring along engine pinging, (lean engine in another way)
brings up the same codes of oxygen sensor issues, but still no out of calibration Mass Air Flow codes.
I have seen all of the items on the fuel side as listed and the mass Air Flow issue, I have not seen any of the vaccum leak items though, but are a possibility.
The manifolds break and leak for sure, AIC motors do stick and I believe the PCV hoses break, I have not seen these codes set with these for issues yet.
Just some ideas. Broken Wire
Exhaust manifolds leaking, Large intake vacuum leak, PCV hose broken, intake manifold broken or gasket leaking, plenum gasket leaking, power booster leaking vacuum, Idle Air Control motor sticking open.
Mass Air Flow issues usually bring along engine pinging, (lean engine in another way)
brings up the same codes of oxygen sensor issues, but still no out of calibration Mass Air Flow codes.
I have seen all of the items on the fuel side as listed and the mass Air Flow issue, I have not seen any of the vaccum leak items though, but are a possibility.
The manifolds break and leak for sure, AIC motors do stick and I believe the PCV hoses break, I have not seen these codes set with these for issues yet.
Just some ideas. Broken Wire
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Junior User
Joined: Jul 2004
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Thanks guys, for the advice but i need some more. My SES light came on again and i bet it is the same codes. My question is where do i start with the fuel filter or start checking for vaccum leaks. I listened for exhaust leaks tonight but didnt' hear anything so i dont' think it is that.If i get time i will check the intake manifold and all the vaccum lines.
By the way still running factory intake.
By the way still running factory intake.
Senior User
Joined: Jun 2005
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From: Bridgewater, NJ
To verify that there are indeed no exhaust leaks, while the engine is running put a rag or a gloved hand over the exhaust and see if any noise occurs in the exhaust system, and that the pressure of the exiting gas does not change as you cover it. I had a similar problem, and it was because my mass air sensor was affected by an aftermarket intake. After spraying it down with electrical contact cleaner, the problem went away. (I was getting the same lean codes and my short & long term fuel trims were way off).
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Junior User
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I checked my vaccum lines yesterday and found one that had burned completly through. So i went to Advance Auto Parts last night and replaced it. I hope that will solve my problem.
Thanks for the help
Thanks for the help
