Question about 2004 Chevrolet Impala

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Why would code p0171 coming up on my car

I have replaced pvc valve cleaned throttle body and mass airflow sensor

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Code p0171 refers to system too lean, bank 1===causes --intake/exhaust leak --AIR system---MAF/VAF sensors--fuel pressure/pump--injectors---HO2S sensor
as the HO2S sensor is the first sensor to inform the ECM of the mixture setting problem I would consider changing it first. Have the fuel pressure checked as there may be a problem with the pressure regulator in the manifold and lastly have the injectors checked for tip blockages.

Posted on Nov 23, 2014

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How do I eliminate a p0171 code 2004 chevy impala 3.8 litre


Google your OBD Codes & study the problem

Then component test to find a problem

TYPE: OBD PO171

Nov 23, 2014 | Cars & Trucks

1 Answer

To start, I coded my engine and got P0171 - Bank 1 System too Lean. From a stop, when I start out I have a sputter. I push the pedal more & there is no engine rev, and no acceleration. Then the engine...


i have had that problem before its most likely a dirty throttle body or a bad throttle position sensor or air idle control sensor some times cleaning the sensors will work before changing them

Aug 10, 2013 | 2000 Chevrolet Prizm

1 Answer

Hesitation on acceleration


Most common problem is a failed mass airflow sensor. Remove sensor and carefully inspect the sensor for debris building up on the diode. Another possibility is the egr valve may be partially stuck open. The upper intake manifold is made of plastic. The egr gases enter the intake just behind the throttle body inside the plastic intake. It is pretty common for the hot exhaust gases to burn through the plastic and possibly cause coolant to enter combustion chambers. A restricted catalytic convertor from previous engine misfires will accelerate this due to exhaust gases having no place to escape.

Mar 25, 2012 | 2000 Buick LeSabre

2 Answers

I have a 2000 ford windstar with these codes coming up po174 and po171 and yes i have changed all plugs and wires


Changing the plugs and wires is not really your problem. Your vehicle is running to lean which has to do with the fuel mixture. I would say more then likely you have a bad O2 sensor which would cause this but P0171 & P0174 are 2 different banks which is where the reason for it running to lean could be a number of reasons. I would get a can of mass airflow sensor cleaner. Do not let the parts people try to talk you into using brake parts cleaner because this is not good for the sensor. Something (a sensor) is telling your computer in the vehicle to mix the fuel and air incorrectly. Start by cleaning the mass airflow sensor (MAF) and then I would reset the computer and erase the codes and see if it comes back. You may have something as simple as a vacuum leak as well. There could be MANY reasons for this code and there are MANY tests to perform before you start replacing parts. Start with the MAF and look for a vacuum leak as well. That's where I would start and have been doing this for 25 plus years.

Jul 02, 2011 | 2000 Ford Windstar

1 Answer

Po171 code keeps coming up, I changed the fuel filter. Pressure at fuel filter is 45, pressure at fuel rail is 45. Pressure is 50 with pressure relief valve disabled. Diaphram is good at pressure...


did you check the o2 sensor bank 1 ? cause de p0171 code say sistem too lean bank 1 do you need replace this sensor and get a better fuel saving . or maybe is disconected or the o2 sensor wires could by cut o burn, i think about you problem is not the fuel sistem . clean again carefully the maf sensor without broke the tiny couple wires thks

Aug 07, 2010 | Ford F-250 Cars & Trucks

1 Answer

What is code P0171?


P0171

A lean fuel condition can be caused by:

* Low fuel pressure due to a weak pump or leaky fuel pressure regulator. (use a fuel pressure gauge to check fuel pressure at idle)

* Dirty fuel injectors. (try cleaning the injectors)

* Vacuum leaks at the intake manifold, vacuum hose connections or throttle body. (Use a vacuum gauge to check for low intake vacuum)

* Leaky EGR valve. (Check operation of EGR valve)

* Leaky PCV Valve or hose. (Check valve and hose connections)

* Dirty or defective Mass Airflow Sensor (MAF). (Try cleaning the MAF sensor wires or filament with aerosol electronics cleaner. Do NOT use anything else to clean the sensor, and do not touch the sensor wires

Jul 14, 2010 | 2002 Kia Sportage

1 Answer

99 CHEVY trouble shoot code P0171


LEAN TROUBLE CODES (P0171 or P0174) A code P0171 or P0174 indicate the engine is running lean. This means there is too much air and/or not enough fuel. You can confirm the engine is running lean by looking at Short Term Fuel Trim (STFT) and Long Term Fuel Trim (LTFT). Normally, STFT and LTFT should be plus or minus 8 from zero. If STFT and/or LTFT are more than about +10 or higher, it indicates the engine is running LEAN. Negative numbers (-10 or more) indicates the engine is running RICH. A lean fuel condition can be caused by:

* Low fuel pressure due to a weak pump or leaky fuel pressure regulator. (use a fuel pressure gauge to check fuel pressure at idle)

* Dirty fuel injectors. (try cleaning the injectors)

* Vacuum leaks at the intake manifold, vacuum hose connections or throttle body. (Use a vacuum gauge to check for low intake vacuum)

* Leaky EGR valve. (Check operation of EGR valve)

* Leaky PCV Valve or hose. (Check valve and hose connections)

* Dirty or defective Mass Airflow Sensor (MAF). (Try cleaning the MAF sensor wires or filament with aerosol electronics cleaner. Do NOT use anything else to clean the sensor, and do not touch the sensor wires)

______________________________-- Causes A 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 Solutions Possible 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

Jan 02, 2010 | 2001 Dodge Ram 1500 Truck 2WD

2 Answers

Code 171 and engine light is on


--BANK 1 = DTCs P0171 (lean) and P0172 (rich)

-Check intake air system for leaks, obstructions and damage.
-Check air cleaner element, air cleaner housing for blockage.
-Verify integrity of the PCV system.
-Check for vacuum leaks.

I would try cleaning the Mass Airflow Sensor first. A dirty Mass Airflow Sensor is a common problem for triggering PO 171 & 174 codes.

Good luck and keep me posted.

Oct 21, 2009 | Chevrolet Colorado Cars & Trucks

3 Answers

F150 stalls out at intersections.


Check there are no air leaks on the air intake system. - check all the clamps/hoses etc that may have been removed to replace airflow sensor.

Jul 17, 2009 | 2004 Ford F150

1 Answer

2001 2.0 jetta manual tranny engine light on


Here are the test procedure for a PO171 code.

1. Check and verify there are no vacuum leaks or unmetered air leaks.

2. Check and verify air filter, all inlet screens and throttle body are clear and clean (never use an aerosol cleaner to clean a throttle body, damage to the throttle body electronics may result. Use a rag dampened with cleaner to wipe the throttle clean)

3. Check and verify fuel pressure is 36 PSI at idle with vacuum to the fuel pressure regulator.

4. Check Mass Airflow Sensor (MAF) Grams/Second (G/S) readings as follows:

Idle (about 830 RPM) 3.5 G/S or more (4 to 4.5 G/S preferred).

2500 RPM no load, 9 to 15 G/S (11 to 12 G/S preferred).

Wide Open Throttle (WOT) road load (drive vehicle at 45 MPH in 3rd gear and perform a WOT acceleration, observe maximum indicated MAF G/S readings) 90 or more G/S should be present, (prefer above 100 G/S).

A MAF that exhibits consistently lower than normal G/S readings can cause a P0171 code to set. Please let me know if this information is helpful. Positive feedback is appreciated. Thank You!

Mar 21, 2009 | 2001 Volkswagen Jetta TDI

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