Q: 2011 Pathfinder Fluctuating idle, stalling, no power when accelerating

asked by on March 10, 2017

2011 Nissan Pathfinder 4x4. Just purchased it 2 weeks ago but had to bring it in for service shortly thereafter. I'm having a couple problems with it. 1) It has a fluctuating idle. They changed out the MAF and its still doing it. Checked for vacuum leaks and none were found. 2) The other day went out around the block, and the vehicle lost all power. I would push on the gas and there would be a lag between that and when the RPMs would go up. It would go up to 2500 and then bounce there but the car wouldn't move forward. My wife drove it later and she said it stalled, and had the same symptoms after. 3) Got out of the car with my wife in the drivers seat, opened the hood, and watched the throttle cable. She would floor it (in park), it would let out a sound like a blow off valve, then bounce the rpms at 2500. There would be a lag between the time that the rpms would go up and the plastic piece on the cable would move. I have videos of all this. Please help because the dealer can't help.

My car has 112000 miles.
My car has an automatic transmission.

Hi There, It sounds like you may have a dirty or failing idle air control valve causing your engine idle to fluctuate. The idle air control valve is a small valve on the engine’s intake system that reads the air intake as it comes into the motor. This is controlled by the car’s ECM which uses this information to make adjustments to the air/fuel ratio depending on various inputs such as outside air temperature, intake air temperature, load and various other things. As you accelerate, your car’s engine is receiving a much higher dose of fuel than when at idle and conversely, when you let off the gas pedal, there is a sudden change in this fuel supply as a result of your foot letting off the pedal. When this happens, the job of the idle air control valve is to bring this deceleration down to a slow and smooth idle rather than suddenly cutting off the fuel supply causing the motor to die. When the idle air control valve is not working properly, this cause a disruption in this process resulting in the engine not being able to idle properly.

The other possibility may be that you have a faulty MAP sensor. The Manifold Absolute Pressure (MAP) sensor senses engine load and generates a signal that is proportional to the amount of vacuum in the intake manifold. The engine computer then uses this information to adjust ignition timing and fuel enrichment. When the engine is working hard, intake vacuum drops as the throttle opens wide. The engine takes in more air, which requires more fuel to keep the air/fuel ratio in balance. When the computer reads a heavy load signal from the [MAP sensor]((https://www.yourmechanic.com/services/manifold-absolute-pressure-sensor-map-sensor-replacement), it adjusts the fuel mixture to slightly more rich than normal so the engine can produce more power. The computer will then retard (back off) ignition timing slightly to prevent detonation that can damage the engine and decrease performance. This may also be caused by other closely related components such as a dirty or failing mass air-flow sensor, a faulty throttle position sensor or potentially a vacuum leak. I would recommend having an expert from YourMechanic come to your location to diagnose and inspect your vehicle.

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