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Pee Zero One Seven One Bee.


Naterenfo1

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:temper: I am so frustrated with my 4.0...
I have gotten these codes all winter... cleared and reset, then it happens again...
P0171B
and
P0174B
Here's what I got:
98 Ranger 4.0V6 2wd Ext cab. I swapped tire sizes mid winter, from a 225/75/14 to a 235/75/15 AT tire. On a full tank during summer, I was averaging about 260-300 miles on a tank, depending how I felt that week. Driving similiar to summer driving, little to no Idle time, and driving about 10-30 miles a day, I average 180-220 on a full tank of gas. WTF?

My 02 sensors appear to be working fine, haven't pulled them, but the readings on my code reader are within spec.

Anyone have an idea?
I have scanned the site quite a bit, and haven't found too terribly much. I have sprayed around my intake with carb cleaner, no bogging or revs, I also sprayed over vacuum lines and no bogging or rev's. Can someone link me to MAFS testing procedures? or give me voltage specs?

Any and all help is appreciated!
-Nate
 


AgPete139

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Pretty much, your system is running too lean.

Have you tried cleaning your MAF? You really don't recalibrate these things, but if you are looking for voltage numbers from the signal wire, hopefully someone else can chime in. My 4.0L is also in the shop, and may be a different reading.

As for the cleaning process, take out your MAF / housing and spray it generously with carb cleaner and remove the oils & other potential grime that may be showing a different reading than desired. This is especially habitual with aftermarket air filters, like K&N. It will read differently...I really must suggest this first, since it's the quickest & easiest solution.

Another thing: change your fuel filter. Cheap @ $4.50, should be done yearly for maintenance, and helps with gas mileage. Have you done this lately?

And lastly, another thing that could cause a lean mixture is a bad intake manifold gasket. But, usually one bank goes out, not always both (which is why I suggest those 2 other solutions first, and cheaper easier). Your lower intake manifold gasket (the reason for spraying the carb cleaner near the gasket regions on the block & listen for idle) may not get down far enough or drip down near the leak to help you out.

Let us know how it goes.



Pete
 

97fordrunner

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+1 and welcome to TRS glad to have some more people from the cities on here
 

Naterenfo1

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Thanks for the help guys!
@Pete, I changed out the fuel filter not too long ago, it was actually last spring. It was a Wix filter, so I am assuming its still fine. I suppose I shall change that anyway.
I found this article on ALLDATA and wanted to help out some other members pertaining to this issue.

LIGHT TRUCK:
1990 BRONCO II
1990-99 RANGER
1991-99 EXPLORER
1994-96 BRONCO

ISSUE
This TSB article is a diagnostic procedure to address vehicles that exhibit lean driveability symptoms and may or may not have any Diagnostic Trouble Codes (DTCs) stored in memory.

MASS AIR FLOW (MAF) DISCUSSION
MAF sensors can get contaminated from a variety of sources: dirt, oil, silicon, spider webs, potting compound from the sensor itself, etc. When a MAF sensor gets contaminated, it skews the transfer function such that the sensor over-estimates air flow at idle (causes the fuel system to go rich) and under-estimates air flow at high air flows (causes fuel system to go lean). This means Long Term Fuel Trims will learn lean (negative) corrections at idle and learn rich (positive) corrections at higher air flows.

If vehicle is driven at Wide Open Throttle (WOT) or high loads, the fuel system normally goes open loop rich to provide maximum power. If the MAF sensor is contaminated, the fuel system will actually be lean because of under-estimated air flow. During open loop fuel operation, the vehicle applies Long Term Fuel Trim corrections that have been learned during closed loop operation. These corrections are often lean corrections learned at lower air flows. This combination of under-estimated air flow and lean fuel trim corrections can result in spark knock/detonation and lack of power concerns at WOT and high loads.

One of the indicators for diagnosing this condition is barometric pressure. Barometric pressure (BARO) is inferred by the Powertrain Control Module (PCM) software at part throttle and WOT (there is no actual BARO sensor on MAF-equipped vehicles, except for the 3.8L Supercharged engine). At high air flows, a contaminated MAF sensor will under-estimate air flow coming into the engine, hence the PCM infers that the vehicle is operating at a higher altitude. The BARO reading is stored in Keep Alive Memory (KAM) after it is updated. Other indicators are Long Term Fuel Trim and MAF voltage at idle.

Symptoms
^ Lack of Power
^ Spark Knock/Detonation
^ Buck/Jerk
^ Hesitation/Surge on Acceleration
^ Malfunction Indicator Lamp (MIL) Illuminated -
DTCs
P0171, P0172, P0174, P0175 may be stored in memory
OBDII DTCs
^ P0171, P0174 (Fuel system lean, Bank 1 or 2)
^ P0172, P0175, (Fuel system rich, Bank 1 or 2)
^ P1130, P1131, P1132, (HO2S11 lack of switching, Bank 1)
^ P1150, P1151, P1152, (HO2S21 lack of switching, Bank 2)
OBDI DTCs
^ 181, 189 (Fuel system lean, Bank 1 or 2)
^ 179, 188 (Fuel system rich, Bank 1 or 2)
^ 171, 172, 173 (HO2S11 lack of switching, Bank 1)
^ 175, 176, 177 (HO2S21 lack of switching, Bank 2)
^ 184, 185 (MAF higher/lower than expected)
^ 186, 187 (Injector pulse width higher/lower than expected)

1. Look at the BARO PID. Refer to the Barometric Pressure Reference Chart in this article. At sea level, BARO should read about 159 Hz (29.91 in. Hg). As a reference, Denver, Colorado at 1524 meters (5000 ft.) altitude should be about 144 Hz (24.88 in.Hg). Normal learned BARO variability is up to +/- 6 Hz (+/- 2 in. Hg.). If BARO indicates a higher altitude than you are not at (7 or more Hz lower than expected), you may have MAF contamination. If available, Service Bay Diagnostic System (SBDS) has a Manifold Absolute Pressure (MAP) sensor that can be used as a barometric pressure reference. Use "MAP/BARO" test under "Powertrain," "Testers and Meters." Ignore the hookup screen. Connect GP2 to the reference MAP on the following screen.

2. On a fully warmed up engine, look at Long Term Fuel Trim at idle, in Neutral, A/C off, (LONGFT1 and/or LONGFT2 PIDs). If it is more negative than -12%, the fuel system has learned lean corrections which may be due to the MAF sensor over-estimating air flow at idle. Note that both Banks 1 and 2 will exhibit negative corrections for 2-bank system. If only one bank of a 2-bank system has negative corrections, the MAF sensor is probably not contaminated.

3. On a fully warmed up engine, look at MAF voltage at idle, in Neutral, A/C off (MAF V PID). If it's 30% greater than the nominal MAF V voltage listed in the Powertrain Control/Emissions Diagnosis (PC/ED) Diagnostic Value Reference Charts for your vehicle, or greater than 1.1 volts as a rough guide, the MAF sensor is over-estimating air flow at idle.

4. If at least two of the previous three steps are true, proceed to disconnect the MAF sensor connector. This puts the vehicle into Failure Mode and Effects Management (FMEM). In FMEM mode, air flow is inferred by using rpm and throttle position instead of reading the MAF sensor. (In addition, the BARO value is reset to a base/unlearned value.) If the lean driveability symptoms go away, the MAF sensor is probably contaminated and should be replaced. If the lean driveability symptoms do not go away, go to the PC/ED Service Manual for the appropriate diagnostics.

After replacing the MAF sensor, disconnect the vehicle battery (5 minutes, minimum to reset KAM, or on newer vehicles, use the "KAM Reset" feature on the New Generation Star (NGS) Tester and verify that the lean driveability symptoms are gone.


PS- I cleaned up my MAF sensor today, using the method that Pete told me, and also disconnected the battery for 5 minutes to reset the computer data. I drove about 10 miles and no check engine light as of yet- Acceleration seemed a little better as well! so hopefully all is well! I will fill up my gas tank tomorrow, and run a full tank of gas through and let you know how many miles I got on the tank. Hopefully I can help some of you out!!!!
Thanks for reading!
-Nate
 
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AgPete139

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Have you tried cleaning your MAF? You really don't recalibrate these things, but if you are looking for voltage numbers from the signal wire, hopefully someone else can chime in. My 4.0L is also in the shop, and may be a different reading.

As for the cleaning process, take out your MAF / housing and spray it generously with carb cleaner and remove the oils & other potential grime that may be showing a different reading than desired. This is especially habitual with aftermarket air filters, like K&N. It will read differently...I really must suggest this first, since it's the quickest & easiest solution.


Did you take the 10 mins time to clean your MAF first?




:icon_twisted:
 

Naterenfo1

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UPDATE- So far so good! No check engine light as of yet *fingers crossed* we had a couple pretty cold mornings, and no light still! I have driven about 50 miles on my fresh tank, and the fuel needle is about perfectly flush with the "F" line on the fuel gauge. I also currently have a snowmobile in the back of the truck, so the added weight will for sure take down some fuel economy as well.

Hopefully this worked! :headbang:
-Nate
 

97fordrunner

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Glad to hear it. So what was the final fix? cleaning the MAF?
 

Naterenfo1

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Final fix for me was Cleaning the MAF by removing the 4 bolts holding in to the housing, the C clamp holding the hose on, disconnecting the sensor, and spraying a liberal amount of carb cleaner in the sensor. After I felt it was clean, I sprayed it again and let it dry. Then again! and let it dry. I bolted the air filter box back on, connected it back to the intake hose, Tightened the clamp, connected the sensor, and then disconnected the ground terminal of my battery for 10-ish minutes to reset the computer and MAF info. reconnected the battery, changed the presets on my stereo back fired her up and haven't had the code come up yet!
 

trx450r

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hi pete, i have a 99 4.0 xlt 4x4 ranger that has been throwing the lean on bank 1 code at first then on both banks after about a month. it also has been sucking coolant throught the rad resivor which leads me to belive i have a bad lower intake gasket. I was wondering if bad intake gaskets could cause a sticking throttle situation because my rpms will stick at 1500- to whereever my foot leaves off it and holds for a few seconds til it slowly decreases by 100rmp till it hits 1200rmp then surges again. any input would be great. thanks
 

adsm08

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Well an air leak at the intake gaskets would cause a high/surging idle and a lean condition.

Loss of coolant would indicate a leak or a head gasket, and a blown head gasket can also set lean codes.

Check the oil, if it looks milky you have issues.
 

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