Possible reasons for the drop in speed when turning on the automatic transmission:
*Throttle Position Sensor Problems: A faulty sensor can send incorrect throttle position data to the Engine Control Module (ECM), causing the engine speed to adjust incorrectly.
* Vacuum Leak: A vacuum leak can cause a loss of pressure needed to operate the engine’s drive trains, including the throttle valve. This may cause a drop in rpm.
* Malfunctioning Engine Control Module (ECM): The ECM is responsible for controlling the engine and transmission. A malfunction in the ECM may result in incorrect speed control.
*Transmission Problems: Wear or other transmission problems can cause increased resistance or slippage, causing RPM to drop.
* Torque converter problems: The torque converter is responsible for transferring power from the engine to the transmission. A faulty or worn torque converter can cause a drop in rpm.
* Entry Speed Sensor Problems: A faulty entry speed sensor may send incorrect vehicle speed data to the ECM, causing the engine speed to adjust incorrectly.
* Crankshaft Position Sensor Problems: A faulty crankshaft position sensor may send incorrect crankshaft position data to the ECM, resulting in incorrect ignition and RPM adjustments.
Steps to resolve the issue:
1. Check Throttle Position Sensor: Use an OBD2 scanner or multimeter to check the throttle position sensor output.
2. Check the vacuum system: Use a vacuum gauge to check for leaks or insufficient pressure.
3. Check ECM: Use OBD2 scanner to check ECM related trouble codes.
4. Check the transmission: Check the transmission oil for color, odor, or metal particles.
5. Check the torque converter: Have a mechanic perform a more thorough diagnosis and repair.
6. Check Input Speed Sensor: Check the sensor wiring and use an OBD2 scanner to check the input signal.
7. Check Crankshaft Position Sensor: Check the sensor wiring and use an OBD2 scanner to check the input signal.