* Faulty Throttle Position Sensor (TPS): This sensor tells the engine control module (ECM) the position of the throttle. A malfunctioning TPS could send a false signal indicating the throttle is open, even when it's not, leading to unintended acceleration.
* Sticky or Faulty Throttle Body: The throttle body is the mechanism that controls airflow into the engine. If it's sticking or malfunctioning, it might remain partially open, causing the engine to rev and the car to move.
* Transmission Problems: A problem within the automatic transmission itself, such as a faulty valve body or internal mechanical issue, could cause the transmission to engage and the car to move unexpectedly. This is a more serious and potentially expensive issue.
* Cruise Control Malfunction: Although less likely, a malfunctioning cruise control system could inadvertently engage and cause unintended acceleration. This is usually accompanied by the cruise control light being illuminated.
* Vacuum Leak: A significant vacuum leak can affect the proper operation of the engine and transmission, potentially leading to erratic behavior including unintended acceleration.
* Faulty ECM (Engine Control Module): While less common, a faulty ECM could misinterpret sensor data or send incorrect signals to the engine and transmission, resulting in unintended acceleration.
* Worn or Damaged Shift Cable (Manual Transmission): Though less likely on an Altima which usually has an automatic transmission, a worn or damaged shift cable on a manual could cause the car to move unexpectedly.
What to do:
* Do not drive the car: This is a safety hazard. The problem needs to be diagnosed and repaired by a qualified mechanic immediately.
* Have it towed to a reputable mechanic or dealership: Attempting to diagnose and fix this yourself is dangerous and could worsen the problem.
Ignoring this issue is incredibly dangerous. Get it checked immediately to avoid accidents.
