* Fuel injectors: When cold, the fuel can be thicker and injectors may struggle to atomize it properly. This is especially true if the injectors are worn or dirty. They may be delivering an inconsistent fuel spray, leading to a rough idle. This is a common problem on older cars.
* Choke (if equipped): Older cars might have a choke system. If the choke isn't working correctly (stuck, partially closed, or malfunctioning), it can lead to a rich or lean fuel mixture when cold, causing rough running. While less common on 93 models, it's possible.
* Mass Airflow Sensor (MAF): The MAF sensor measures the amount of air entering the engine. If it's dirty or faulty, it can provide incorrect readings, especially when cold, resulting in an improper air/fuel mixture.
* Throttle Position Sensor (TPS): Similar to the MAF sensor, a faulty TPS can provide inaccurate readings to the engine computer, affecting fuel delivery and idle speed when cold.
* Ignition System: Worn spark plug wires, failing ignition coil(s), or weak spark plugs can cause misfires, especially noticeable when the engine is cold and components haven't warmed up to their optimal operating temperature. These are less likely to ONLY be a problem when cold, however, as they often manifest when hot as well.
* Vacuum Leaks: A vacuum leak can disrupt the fuel/air mixture, and this is often more pronounced when the engine is cold.
Troubleshooting Steps:
1. Check for trouble codes: Use an OBD-II scanner to see if any diagnostic trouble codes (DTCs) are stored in the engine control module (ECM). This is the easiest first step.
2. Inspect spark plugs and wires: Look for signs of wear, damage, or corrosion. Consider replacing them if necessary; this is a relatively inexpensive fix.
3. Clean the MAF sensor: Carefully clean the MAF sensor with MAF sensor cleaner (following the cleaner's instructions). Avoid touching the sensor's element.
4. Check the fuel filter: A clogged fuel filter can restrict fuel flow, especially when the fuel is thicker due to cold temperatures.
5. Test the fuel pressure: This requires a fuel pressure gauge and might necessitate professional assistance. Low fuel pressure can be a significant cause.
6. Inspect vacuum hoses: Look for cracks, leaks, or loose connections in the vacuum hoses.
If you are not mechanically inclined, it's best to take your car to a qualified mechanic. They have the tools and expertise to diagnose the problem accurately and efficiently. Starting with the simple and less expensive checks (spark plugs, MAF sensor cleaning, trouble codes) can save money before moving to more involved diagnostics.
