6
votes
P0171 and Fuel Trims
Great question, you supplied enough data to give direction and this is a common problem.
This pattern of fuel trim behavior, higher positive at idle than at cruise speeds, is commonly seen when the ...
- 11.7k
2
votes
How to fix Check engine error P0171 on VW Tiguan?
As Jupiter states in the comment, vacuum leaks are the most likely cause (particularly around the PCV valve and EGR valve). Be sure to listen for a hissing sound of air throughout the engine ...
- 2,200
2
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Fuel Trim Readings
@Fred Wilson's comment is right on the money, high, positive long term fuel trims at idle that reduce at higher engine speeds indicate the presence of higher-than-normal unmetered air.
The fact that ...
- 39.2k
2
votes
Accepted
P0171: what to look at next, after MAF, O2 senors, fuel filter, and vacuum?
The main cause of most P0171 codes on the 4runner is the MAF sensor, which also has the air temperature sensor on it, a faulty air temperature sensor on your MAF can cause a running rich problem. It's ...
- 17.7k
1
vote
Vehicle not storing freeze frame data when it sets OBD P0171 code
I can only speculate why no freeze frame data is being stored with the p0171. My "guess" would be that it is a 2 trip code, and you are seeing a pending code on the first trip.
When it comes to ...
- 634
1
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PO171 trouble code at idle
Here's another possible cause, that I discovered while preparing to clean the Mass Air Flow (MAF) sensor using MAF cleaner spray; big as day, saw a big crack in the hose from the MAF body to the ...
- 364
1
vote
PO171 trouble code at idle
If the throttle body, MAF/MAP was cleaned, or other fuel/emission components replaced, the throttle relearn needs to be done.
Disconnect the negative cable from the battery (cover the post with
a ...
- 9,005
1
vote
Corolla gives me a P0170 code
LTFT at 29.7% seems mighty high. I'd start by looking for unmetered air leaks aka "vacuum" leaks.
Unmetered air might be fooling the primary O2 sensor - so called "false lean". Easy to check and a ...
- 12.4k
1
vote
P0171 and P0174 in 2008 Range Rover HSE
In general, these codes indicate that the ECU receives information about fuel mixture being too lean, ie. too much oxygen, too little fuel. Therefore, it is trying to compensate by adding more fuel (...
- 193
1
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What do you think of these spark plugs?
The end with the spark gap is primary importance . What are you burning ? I have not seen that much crud since the leaded gasoline days. This much fouling would be typical of leaded fuel , not a worst ...
- 3,733
1
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What does the fluctuating needle means in this vacuum test? Video uploaded to youtube
The fluctuation means a problem with a valve not seating properly or valve that is burned or warped. I can hear a valve tapping noise in your video (starts about 0:10 sec.). It's time for a ...
- 2,200
1
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Why my long fuel trim readings are higher than short trim ones?
You are right the STFT will replace the LTFT after a given amount of time. IIRC, the LTFT is the adjustment to the tune itself to compensate for fueling issues over a longer period of time. If the ...
- 162k
1
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Mazda 323 / Protege 2001 power problem
My suggestion is to look at the throttle body, specifically at the throttle position sensor (TPS). You need to see if it has the right output. You can either do this by looking directly at the ...
- 162k
1
vote
Help with P0171 code
P0171 is a "System too lean" error code. This is caused by the engine receiving more air than fuel so it compensates by adding more fuel (hence positive LTFT and STFT). A common way to diagnose ...
- 51
1
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P0171 "System too lean" error in Vauxhall Corsa 2011 - comes on intermittently
Ugh.. Corsa-Ds seem to throw this code for everything, sometimes just because the day ends in a "Y"
A failing Manifold Absolute Pressure (MAP) sensor is the usual culprit - particularly with the ...
- 10.5k
1
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P0171: what to look at next, after MAF, O2 senors, fuel filter, and vacuum?
Replace the MAF sensor. In looking at your freeze frame data, LTFT shouldn't be that high.
Look at Airflow g/s and it should inrange of 3.0 - 4.5.
Since your freeze frame is at 42mph rev motor up to ...
- 11
1
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P0171: what to look at next, after MAF, O2 senors, fuel filter, and vacuum?
LTFT1 39.8
This sticks out like a burr. The lambdas are sensing 40% more air than what the MAF/MAP is measuring, either due to unmetered air or insufficient fuel.
Given that the MAF and lambda ...
- 39.2k
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