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

asked by on August 19, 2016

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.

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