I have replaced all fuel injectors, the MAP sensor, the MAF sensor, the fuel pressure regulator, and my Buick wants to putter and stall when it comes to an idle. What could be causing this!? I need answers, $500 later and it's still not running right. The fuel pump is working fine, supposably everything is working fine because the car is not spitting out any codes. But there is something wrong because it keeps acting this way. HELP!!

It is a generic OBD2 power train Code. The same solution could be applied to all other vehicles as well.
Error Code: P0171
Description:
Fuel Trim (FT), System too Lean, Bank 1
Possible Causes:
- Fuel pump pressure too high or regulating valve stuck closed.
- Intake/ exhaust leak.
- Secondary air injection (AIR) system.
- Manifold absolute pressure (MAP) sensor.
- Mass air flow (MAF) sensor.
- Fuel pressure/pump.
- Fuel Injector(s).
- Evaporative emission (EVAP) canister purge valve.
- Heated oxygen sensor (HO2S).
Solutions:
-Usually, simply cleaning the Mass air flow (MAF) sensor helps solve the problem.
- It is best to take MAF off and spray it with electronics cleaner or high flash point solvent.
- Inspect all vacuum and PCV hoses, replace if necessary.
- Check for a dirty fuel filter and proper fuel pressure.

why did you change mass air flow sensor ? do you have coil packs, any codes stored in ECM ? something is telling it to go full lean ! ? another sensor, OXYGEN SENSOR, MAP SENSOR ? aftermarket MAF sensors are garbage, you might need a stock , OEM , MAF !!!!!!!!! I would , my 87 buick gn boged when I replaced my MAF , I got a new OEM , STOCK , MAF, exact replacement, it ran wonderful !!!! again !

Have you checked the cam sensor? Also does that vehicle have a "throttle position sensor"? Some cars use both MAP and MAF sensors, not sure about your particular vehicle but if it is one of those, cleaning the MAF wouldn't hurt. Good luck.

You have a MAF and MAP, The mass air flow signal varies with engine load.It is attatched to throttle body. This if it is the primary signal can cause the problem you desribe try and disconnect it and see if it idles properly. The next item you need to inspect is the MAP ,manifold air pressure this is a back up for the MAF sensor.If this sensor fails you will not accelerate correctly and stall out flooding the vehicle with fuel. This monitor the MAF and your EGR. If the EGR valve is stuck open the vehicle stumble and stall out and affect the performance of the MAF and MAP.Make sure your MAP is connected and the vacuum hose is attatch this item is located at top rear engine compartment near fuel injectors

CHECK THE AIR INTAKE TUBE FOR TEARS OR LEAKS. A LARGE VACUUM LEAK WILL CAUSE THIS.

Sounds like a bad fuel pressure regulator.Check for fuel in the vacuum line going to regulator.

Hi Jonah,

I have the same problem and it only propped up after i had my exhaust manifold repaired, do you think the mechanic didnt do the weld it right?

James
2001 Saturn L200

Trouble Code: P0171 (3.8L V6 VIN 1 Auto)
Fuel Trim System Lean (Bank 1) Print this code data Number of Trips to Set Code: 2
OBD II Monitor Type: CCM Details
Indicators: MIL Details

• Fuel Details
• MIL Details

Trouble Code Conditions:
DTC P0101-P0103, P0107, P0108, P0121-P0123, P0130-P0138, P0140, P0141, P0201-P0206, P0300, P0401-P0405, P0410, P0440-P0446, P0506, P0507, P1404 or P1441 not set, engine started, vehicle driven at less than 82 mph at 550-4000 rpm, BARO sensor over 70 kPa (10.1 psi), ECT sensor from 68-230ºF, IAT sensor from 64-158ºF, MAF sensor from 2.8-150 gm/s, MAP sensor from 16-105 kPa (2.6-15.2 psi), fuel level over 10%, and the PCM detected the Long Term fuel trim value was more than +20% for 6 seconds. The PCM controls the air/fuel metering system to good overall fuel economy, driveability, and emission control. During open loop, the PCM determines fuel delivery based on sensor signals, without the oxygen sensor input. During closed loop, the PCM adds oxygen sensor inputs to calculate Short and Long term fuel trim fuel delivery adjustments. Short Term fuel trim values change rapidly in response to changes in the oxygen sensor signals. Long Term fuel trim makes coarse adjustments in order to maintain an air/fuel ratio of 14.7:1.

Possible Causes:

• Air leaks in intake manifold, exhaust pipes or exhaust manifold
  
• Fuel control sensor is out of calibration (ECT, IAT or MAF)
  
• Low fuel pressure (fuel filter clogged, pressure regulator failure)
  
• One or more injectors restricted or pressure regulator has failed
  
• HO2S element is contaminated, deteriorated or has failed
  
• Vacuum hose is disconnected, broken, leaking or loose
  

Troubleshooting:2002 Buick Park Avenue, 3.8L, P0171

start right back up? if it does , then pull the vacuum hose off the fuel pressure regulator and and a stall . if gas comes out of the regulator/and hose. Thats the problem , bad diaphram in fuel pressure regulator!! $45.00 @ auto parts store , snapring pliers is only tool you'll need!! ($5.00 tool) Chep and easy!! :) Hope this helps!! Richie

Wow, That has gotta be a pain. The Maf sensor regulates the fuel supply needed for proper air fuel ratio by telling ecu how muc air is moving thriugh the intake. Check it first, Then the TPS. Good Luck.