High-Probability Suspects:
* Mass Airflow Sensor (MAF) or Throttle Position Sensor (TPS): These sensors tell the engine's computer how much air and throttle opening there is. A faulty sensor will send inaccurate information, leading to a rich or lean fuel mixture and erratic engine operation (surging). This is a common culprit for surging and check engine lights.
* Dirty or Faulty Fuel Injectors: Clogged injectors can cause inconsistent fuel delivery, resulting in surging and poor performance. Likewise, faulty injectors can spray improperly, leading to the same problem.
* Ignition System Problems: Worn spark plug wires, a failing distributor cap or rotor (if applicable), or bad spark plugs can cause misfires, leading to surging and a check engine light.
* Vacuum Leaks: A leak in the vacuum system can disrupt the airflow to various engine components, resulting in uneven running and a check engine light.
Less Likely, but Possible:
* Transmission Issues: While less likely to directly cause a check engine light, a transmission problem *could* contribute to surging. However, transmission problems usually manifest differently than solely engine surging.
* Computer/ECM Problems: A failing engine control module (ECM) is a less common but possible cause. This is a more expensive repair.
What to Do:
1. Read the Diagnostic Trouble Codes (DTCs): The check engine light is storing trouble codes. You'll need an OBD-II scanner to read these codes. Auto parts stores often offer free code reading services. The codes will give you a much more specific indication of the problem.
2. Inspect the obvious: Check for loose vacuum lines, visually inspect the spark plug wires, and look for any obvious signs of damage or wear in the engine bay.
3. Don't ignore it: Continuing to drive the car with a surging engine and a check engine light can cause further damage.
Important Note: Without knowing the specific DTCs, any attempt at a diagnosis is speculative. Getting the codes read is the crucial first step. Once you have those codes, you can then research the specific problem and determine the best course of action. A mechanic can properly diagnose and repair the issue, especially if you're not comfortable working on your own vehicle.
