Question about 2002 Ford F150 Regular Cab

2 Answers

My 4.6 engine is getting 2 codes which tell me Lean mixture on en

My 4.6 engine is getting 2 codes which tell me lean mixture on both engine banks. I changed the fuel filter and cleared the codes. They came back and the engine is still running very rough. Any ideas? Thanks.

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  • bdaniels79 May 07, 2010

    The codes were 171 and 174. I will check for some more vacuum leaks. Thanks.

  • bdaniels79 May 10, 2010

    I took the cowling off of the throttle body so I could reach back behind the motor better and found the 90 degree hose that's only 2-3 inches long that ties the pcv valve from the right side valve cover to the back of the throttle body. This 90 degree rubber hose had a major hole in it. I replaced it and it runs great again. Thanks for all of the info for me. I really appreciate it.

  • bdaniels79 May 27, 2010

    I found the problem!!! the 90 degree rubber hose on the back of the throttle body that connects the hard plastic pipe that goes to the pcv valve on the valve cover had a huge hole it. A vacuum leak from h...!!! I replaced the hose and life is good. Thanks everyone for your help.


2 Answers

What are the codes?
The codes you get,do not tell you what is wrong, or what to replace.
The fuel filter has no role here,unless completely clogged
You need to diagnose the cause,of the codes and symptoms your experiencing

You may have a valve cover,leaking oil onto a spark plug,or a bad coil,thus a misfire and O2 codes, as well as other codes, that will drive you crazy and in the end ,
just go away.

Make sure the ducting from Air Filter to the Throttle Body is in place and no vacuum leaks
You could clean the MAF Sensor --with CRC MAF Cleaner

Let me know what help you need, just too may things I could talk about

Posted on May 07, 2010

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  • Anonymous May 07, 2010

    PO171-System to Lean (Bank1)

    PO174-System to Lean(Bank2)

    I would work on Ignition,Intake Ducts and make sure your O2 Sensors are screwed in tight. In that order

    I would doubt, all the O2 Sensors are slow to react,because you got codes for both banks. More like a vacuum leak near throttle body,effecting all cylinders.

  • JOHN DAVIDSON May 21, 2010



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  • 79 Answers

Does your vehicle have any aftermarket filters or air box, the computers in new vehicles are designed to run on whats provided by the factory,if you have a k n filter your mass airflow sensor is probably plugged by the oil in the filter

Posted on May 27, 2010

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1 Answer

I have two engine codes 171 and 174 engine is running fine how do i repair them

Well code 171 is telling you the fuel mixture is too lean for bank one and code 174 is too lean bank two.
So the most common cause is low fuel pressure.

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P0171 and P0174 Left and Right bank lean trouble codes pulled from ECU. Check Engine Light illuminated.

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The fuel/air mixture is too lean for the entire engine. The fuel pump pressure could be too low. The fuel pump pressure regulator could be at fault. There could be an air leak downstream of the MAF sensor. MAF sensor (hot wire type) could be dirty. Check for intake manifold vacuum leaks. The engine coolant temp sensor and/or the intake air temp sensor could be faulty (stuck at full hot mode).

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2003 Ford Ranger 4x4 extended cab- diagnostics checked and got these codes- P0171, P0174, P0300, P0316. Can you tell me what they mean?

P0171------ system too lean bank#1
Po174------ system too lean bank#2
For these 2 codes, try cleaning the maf sensor (mass air flow), that is mounted in the big black hose that goes from the air filter housing to the throttle plate, if it is dirty, that will cause those 02 sensors to send a signal to the computor to lean the air fuel mixture. If cleaning it doesn't work, the sensors will probably need changing.
P0300---- Random/multiple cylinder misfire
P0316---- Cylinder misfire at start up---- first 100 revolutions.
On those 2 codes, you have to do some testing to find out why there is a misfire.
Possible causes:
dirty/malfunctioning injectors
weak coil pack
fowling spark plugs/wires
Low fuel pressure

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1 Answer


Your sensors are reading correctly so leave them alone. What you have is a fuel delivery issue. Your MAF sensor is telling your engine to lean your fuel mixture. You need to remove and clean or replace (is better) the MAF. But first replace your PVC valve and clean your ERG valve.

Jan 20, 2010 | 2000 Dodge Intrepid

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Diagnostic code #'s p0174,p0171 system to lean bank 1, system to lean bank 2 help

oxygen sensors are telling you that the mixture is too poor on ur sistem need to check its behaviour and see whats causing that lean mixture
hoope this helps

Nov 10, 2009 | 2001 Lincoln Navigator

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A po171 code came on my scanner i need to know

system too lean in bank 1. clean your mass airflow sensor, replace fuel filter. iff all else fails check you fuel pump.

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MY LEXUS IS200 SE engine management light came on had it checked it was sensor 1 bank 2 had it replaced it came on again sensor 1 bank 1 had it replaced it came on again sensor 1 bank 2 HELP!!!!!!

What was the code? lean mixture? If so make sure there is no leak in the exhaust. I have worked on a lexus suv, but it was an 89. It had a lean mixture code. After examination I noticed a exhaust leak which was not apparent at first, there is a section in the exhaust the is very thin, and prone to leakage, causing the lean mixture code.

Jun 30, 2009 | 2001 Lexus RX 300

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