* Shift linkage: The linkage that connects the shifter to the transmission could be worn, bent, or improperly adjusted. This is a common cause. Look for any visible damage or looseness in the linkage.
* Park pawl: This is a mechanical device inside the transmission that engages to hold the vehicle in park. It could be worn, broken, or not engaging properly. This often requires a transmission repair.
* Shift interlock cable or solenoid: This is an electrical component that prevents the vehicle from starting unless the shifter is in Park or Neutral. A faulty cable or solenoid can allow the vehicle to start even if the shifter isn't fully engaged in Park. This is a relatively common problem, especially in older vehicles. The solenoid is usually located near the steering column.
* Transmission problems: While less likely, internal transmission problems could contribute to this issue. This is a more serious and expensive repair.
* Low transmission fluid: While unlikely to be the *sole* cause of it popping out of park, low transmission fluid could exacerbate existing problems in the linkage or pawl. Check your transmission fluid level.
What to do:
1. Safety First: Do not drive the vehicle until the problem is fixed. If it shifts out of park while running, it could roll unexpectedly.
2. Check Transmission Fluid: Check your transmission fluid level and condition. Low or dirty fluid can point to a more serious problem.
3. Inspect the Shift Linkage: Carefully inspect the linkage connecting the shifter to the transmission for any signs of damage, looseness, or misalignment. Look for bent or broken parts.
4. Check the Shift Interlock Cable or Solenoid: This might require some mechanical knowledge or a professional mechanic to diagnose. A faulty solenoid is relatively easy to replace, but a faulty cable could require more extensive work.
5. Professional Diagnosis: If you're not comfortable inspecting the linkage or electrical components, take your Expedition to a qualified mechanic for diagnosis and repair. This is the safest and often most efficient approach. Explain the problem clearly – that it shifts out of park *when you start the engine*.
Ignoring this problem could lead to serious accidents. Addressing it promptly is crucial.
