Codes P0171 and P0174.

[JamesFox]

Code reader shows too lean codes P0171 and P0174 for my '98 4 litre overhead valve.

Engine running well except for howling noise comes from the air intake area. Howling has happened in the past but only during winter temps but has always disappeared when the engine warms up. Howling has been accompanied by a rough idle/stall at low throttle (stopped for a light when the engine is still cold) but the engine can be re-started easily. Some have suggested a faulty IAC but IAC has never been replaced b/c problem is minor

This year I got the check engine light and the howling is happening more frequently. Weather has been cold for several weeks.

Everyone says P0171 and P0174 are tough to diagnose and fix. Any thoughts? Anyone has this related to an engine howling sound?

 

[Sams01XplrSprt]

welcome

 

[aldive]

I see the "welcome specialist" didn't off you any help.

I shall attempt to do so.

P0171 OBD-II Trouble Code
Technical DescriptionSystem Too Lean (Bank 1)

What does that mean?Basically this means that an oxygen sensor in bank 1 detected a lean condition (too much oxygen in the exhaust). On V6/V8/V10 engines, Bank 1 is the side of the engine that has cylinder #1.

Note: This DTC is very similar to P0174, and in fact your vehicle may show both codes at the same time.

SymptomsYou will more than likely not notice any drivability problems, although there may be symptoms such as a lack of power, detonation (spark knock), and/or a hesitation/surge on acceleration.

CausesA code P0171 may mean that one or more of the following has happened:

The MAF (Mass Air Flow) Sensor is dirty or faulty. Note: The use of "oiled" air filters may cause the MAF to become dirty if the filter is over-oiled. There is also an issue with some vehicles where the MAF sensors leak the silicone potting material used to protect the circuitry.
There could be a vacuum leak downstream of the MAF sensor.
Possible SolutionsPossible solutions include:

In the vast majority of cases, simply cleaning the MAF sensor does the trick. Consult your service manual for it's location if you need help. I find it's best to take it off and spray it with electronics cleaner or brake cleaner. Make sure you are careful not to damage the MAF sensor, and make sure it's dry before reinstalling
Inspect all vacuum and PCV hoses, replace if necessary
Check for a dirty fuel filter and proper fuel pressure

----------------

P0174 OBD-II Trouble Code
Technical DescriptionSystem Too Lean (Bank 2)

What does that mean?Basically this means that an oxygen sensor in bank 2 detected a lean condition (too much oxygen in the exhaust). On V6/V8/V10 engines, Bank 2 is generally the side of the engine that doesn't have cylinder #1.

Note: This DTC is very similar to P0171, and in fact your vehicle may show both codes at the same time.



SymptomsYou will more than likely not notice any drivability problems, although there may be symptoms such as a lack of power, detonation (spark knock), and/or a hesitation/surge on acceleration.

CausesA code P0174 may mean that one or more of the following has happened:

The MAF (Mass Air Flow) Sensor is dirty or faulty. Note: The use of "oiled" air filters can cause the MAF to become dirty if the filter is over-oiled. There is also an issue with some vehicles where the MAF sensors leak the silicone potting material used to protect the circuitry.
There could be a vacuum leak downstream of the MAF sensor.
Possible SolutionsPossible solutions include:

In the vast majority of cases, simply cleaning the MAF sensor does the trick. Consult your service manual for it's location if you need help. I find it's best to take it off and spray it with electronics cleaner or brake cleaner. Make sure you are careful not to damage the MAF sensor, and make sure it's dry before reinstalling
Inspect all vacuum and PCV hoses, replace if necessary
Check for a dirty fuel filter and proper fuel pressure

-------------

The howling sound is most likely due to a faulty IAC. You an attempt to clean it, however, it will most likely require replacement.

Good luck in resolving your issues.

 

[BrooklynBay]

Welcome to this forum! I've moved this thread to the EEC-V section. A lot of times these codes are caused by a leaking intake manifold. There are many threads about the 00M12 on this site. You could see if the idle changes if you spray intake cleaner on the side of the intake manifold. Some people have reported that they experience this problem when the engine is cold, and it slowly goes away when it warms up. Seals expand when they warm up. # 51 in my list of useful threads has additional information: http://www.explorerforum.com/forums/showthread.php?t=177975

 

[Hry1914]

following the awful howling sound

This computer stuff is really greek plus to me,. The howling I get is real quite right in the intake box for the air cleaner, I haven't had any real problems, the only code i have is for an O2 exhaust sensor, check engine light has never gone out, but hat's related to a short I'm told BS i say. Simple carb adjustment and I over run the codes enough to clear emission
The only other problem i have is the cooler/ heater fan went out. starting the sensors trace, and following thru with as much as I can, tracers according to the book from the Air filter to "? > DOES anyone know if an engine has been over heated at any time would it retain any "noise", dumb but any engine not repaired correctly may have scars that carry over, like a thin line leak, any pressure behind it may scream a high pitch. and follow the air intake tube to the front of the engine air filter box, making a whirling howling noise !

 

[BrooklynBay]

Welcome to this forum! The idle air control solenoid has been known to make this noise.

 

[BruceMichie]

Had interesting resolve to an issue at my shop with 98 Ford Explorer, codes P0171 & 174. Found no vacuum leaks at the engine; however, there is an evaporative control canister purge value located UNDER the battery. This value had been damaged by battery acid. Replaced it, codes did not return. So far my customer is a happy camper.

 

[goalkeeper21986]

Had both codes, noticed a loose vacuum hose, quick and easy fix lucky for me

 

[expl0rerct]

In my case, my 2000 Explorer XLT with 4.0L SOHC had both P0171 and P0174 codes. As suggested by this post, I bought a can of electrical contact cleaner and cleaned my mass air flow sensor. I also checked and reseated the PCV valve to make sure the fit was snug. I cleared the codes by removing the battery cable negative terminal, and reconnecting it. So far the codes haven't come back for over 300 miles. For the record, I didn't have any rough idling or any indication of leaky upper/lower intake gaskets. I hope this helps. It saved me a lot of money.

 

[2009KVFD976]

Im having the same issue witb my 01 SOHC. already cleaned MAF and air filter (spectre) took it to a shop and they hooked up a smoke machine and smoke was billowing out of the EGR diaphragm, so i replaced it and PCV valve and cleared the codes. and they came back in less than 20mi!! So i replaced intake gaskets and cleared the codes... once again they came back. what else can it be? Loose exh manifold or O2 sensor?