- Idle Air Control (IAC) valve: The IAC valve is responsible for controlling the amount of air that bypasses the throttle body when the engine is idling. If the IAC valve is faulty, it can cause the engine to stall when put in gear.
- Throttle Position Sensor (TPS) The TPS is responsible for sending a signal to the engine computer about the position of the throttle. If the TPS is faulty, it can cause the engine to stall when put in gear.
- Mass Air Flow (MAF) sensor: The MAF sensor measures the amount of air that enters the engine. If the MAF sensor is faulty, it can cause the engine to stall when put in gear.
- Fuel pressure: Low fuel pressure can also cause the engine to stall when put in gear.
Here are some things you can do to troubleshoot the problem:
1. Check the IAC valve. The IAC valve is located on the throttle body. It is a small, round device with a black electrical connector. To test the IAC valve, disconnect the electrical connector and start the engine. If the engine idles smoothly, the IAC valve is faulty.
2. Check the TPS. The TPS is located on the throttle body. It is a small, black sensor with a single electrical connector. To test the TPS, disconnect the electrical connector and start the engine. If the engine idles smoothly, the TPS is faulty.
3. Check the MAF sensor. The MAF sensor is located in the intake tube, just before the throttle body. It is a small, cylindrical device with a black electrical connector. To test the MAF sensor, disconnect the electrical connector and start the engine. If the engine idles smoothly, the MAF sensor is faulty.
4. Check the fuel pressure. The fuel pressure regulator is located on the fuel rail. It is a small, round device with a single vacuum hose connection. To test the fuel pressure regulator, disconnect the vacuum hose and start the engine. If the engine idles smoothly, the fuel pressure regulator is faulty.
If you are unable to troubleshoot the problem yourself, you should take your Xterra to a qualified mechanic for diagnosis and repair.
