Q: Rough idle with DTC P0171, engine stalls unless MAF sensor is unplugged - 2007 Volvo S40 2.4i

asked by on

I am having a problem with the air or fuel system in my car. Check engine light is on with error code 0171. Car seems to run okay when started from cold. After engine is warm, if I turn the car off then start it again, it idles very rough and often stalls.

I removed the MAF sensor and cleaned it with CRC MAF Cleaner, but the same behavior continues. If I unplug the MAF sensor completely, the car seems to start fine. With the MAF plugged in, though, the car will not start or will start, idle rough, and stall.

Is it safe to assume the MAF sensor needs to be replaced or is there something else that could be causing this issue?

My car has 162000 miles.
My car has an automatic transmission.

Your mass air sensor has most likely gone bad and/or is not giving correct data to the computer. Replace the sensor, clear the codes, and retest this.

Was this answer helpful?
The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details
  1. Home
  2. Questions
  3. Rough idle with DTC P0171, engine stalls unless MAF sensor is unplugged - 2007 Volvo S40 2.4i

Get an instant quote for your car

Our certified mechanics come to you ・Backed by 12-month, 12,000-mile guarantee・Fair and transparent pricing

Get a quote

What others are asking

Q: Q: My car jerks when I accelerate

This may be a sign of a dirty or failing mass air flow sensor. The mass air flow sensor reads the air intake as it is mixed with fuel prior to being injected into the motor. When this fails, this...

Q: DPF light, traction and engine lights flashing, car has no pulling power, dense blue/black smoke on each start.

Based on the information you provided, it is possible that a failed seal in the turbo is allowing engine oil into the intake. The result would be increases carbon buildup on your DPF (Diesel Particulate Filter). Usually a flashing Check...

Q: Master cylinder losing fluid and I can't find leak.

It is possible that your brake fluid could be leaking into the power brake booster. This is the big round container that the master cylinder is bolted to. The brake booster operates off of the vacuum created by the engine...

Related articles

How Long Does a Heater Control Valve Last?
Keeping the right amount of coolant in a car is essential in keeping the engine at the right temperature. Failing to have the right amount of coolant or even bad elements...
P0052 OBD-II Trouble Code: HO2S Heater Control Circuit High (Bank 2 Sensor 1)
P0052 code definition HO2S Heater Control Circuit High (Bank 2 Sensor 1) What the...
P2103 OBD-II Trouble Code: Throttle Actuator Control Motor Circuit High
P2103 means there is a fault with the throttle actuator control motor circuit, likely due to a defective electrical component or part.