2005 Nissan Sentra 2.5l Idle Surge – Erratic Idle

The following vehicle had an idle surge from 1500 – 1800 RPM. A new throttle housing was installed to remedy the problem. After the part replacelent, the idle surge became worse.

When the engine is started the idle surges up and down.

No fault codes were stored.
nofaultcodesnissan

When replacing the throttle housing (throttle body) you have to perform an Idle Air Volume Relearn. It is important to follow directions very carefully. If the relearn does not work the first attempt, try again. It has taken me a few relearns in the past to push it through.

Before performing Idle Air Volume Learning, make sure that all of the following conditions are met. Idle Air Volume Learning will fail if any of the following targets are missed for even a moment.

  • Battery voltage: More than 12.9 V (At idle)
  • Engine coolant temperature: 70 – 95 °C (158 – 203 °F)
  • PNP switch: ON
  • Electric load switch: OFF (Air conditioner, headlamp, rear window defogger)
  • Steering wheel straight-ahead position
  • Vehicle stationary
  • Transmission oil warmed-up
  • The following video highlights the idle air volume learning procedure using an advanced scan tool with Nissan factory options. When performing the throttle body adaption portion of the procedure, you will hear the throttle body open and close. If this does not occur, the procedure has failed. Attmept again or correct problem prohibiting relearn.

    If idle air volume learning cannot be performed successfully, check the following items:

  • Throttle valve is fully closed.
  • PCV valve operation.
  • Check that downstream of throttle valve is free from air leakage.
  • When the above items check OK, there may be a defective part prohibiting relearn. Run your diagnostic strategy.

    If the following conditions occur after engine has started, eliminate cause of condition and perform Idle air volume learning again:

  • Engine stalling
  • Errattic idle
  • 1996 Nissan Maxima 3.0 P0105 P1105

    Both fault codes point to the absolute pressure sensor. The absolute pressure sensor is connected to the MAP / BARO switch solenoid valve by a vacuum hose. The sensor detects ambient barometric pressure and intake manifold pressure and sends a voltage signal to the ECM. As pressure increases, voltage rises. The sensor is not used as an input to control the engine management system. It is used only for on-board diagnosis. Therefore you can have fault codes with no drivability complaint.

    You can see both the sensor and switching solenoid have been replaced. The fault codes remained.

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    I went directly to the sensor to backprobe the connector with the key ON and engine OFF. The first wire I tested was the 5 volt reference. The reading I obtained was 4.35 volts. Too low for a 5 volt reference. I wiggled the harness and the voltage changed accordingly. Next I cut the harness sheathing back to reveal damaged wires. 1 completely broken and the others with broken insulation. The harness to the sensor has a very sharp bend in it. Over time the wires degraded and finally failed. A quick harness repair and the fault codes were gone.

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