Possible causes include, but are not limited to:
* Oxygen Sensor (O2 Sensor) Malfunction: A very common cause. The O2 sensor measures the oxygen in the exhaust and helps the engine computer adjust the air/fuel mixture. A faulty sensor leads to poor fuel economy, rough running, and emissions problems.
* Mass Airflow Sensor (MAF Sensor) Problems: The MAF sensor measures the amount of air entering the engine. A malfunctioning sensor can cause a lean or rich fuel mixture, resulting in similar symptoms to a bad O2 sensor.
* Crank Position Sensor (CKP Sensor): This sensor tells the engine computer the position of the crankshaft. A bad CKP sensor can prevent the engine from starting or cause it to run poorly.
* Throttle Position Sensor (TPS): This sensor tells the computer the position of the throttle. A faulty TPS can cause erratic idle, poor acceleration, or stalling.
* Ignition System Issues: Problems with spark plugs, wires, distributor cap, rotor, or ignition coil can trigger the light.
* Exhaust System Leaks: Leaks before the O2 sensor can affect the readings and trigger the light.
* Evaporative Emission System (EVAP) Problems: Leaks in the fuel system's vapor recovery system can cause the light to come on.
* Temperature Sensors: Faulty coolant temperature sensor or intake air temperature sensor can throw off the engine's fuel mixture calculations.
* Catalyst Converter Issues: A failing catalytic converter can cause a variety of problems and illuminate the check engine light.
To diagnose the specific problem:
1. Obtain a Diagnostic Code: Since it's a 1992 model, you likely need to take it to a mechanic with an OBD I scanner to read the diagnostic trouble codes (DTCs). These codes provide clues to the specific problem. Generic OBD readers often won't work on this older system.
2. Visual Inspection: Check for obvious problems like loose or damaged wires, vacuum leaks, and visible damage to sensors.
3. Professional Diagnosis: Given the age of the vehicle and the limitations of the OBD I system, professional diagnosis is often recommended. A mechanic can properly diagnose the fault and repair it efficiently.
Without a diagnostic code, guessing at the cause is unreliable and could lead to unnecessary repairs. Get that code read first!
