* Fuel delivery issues: Cold weather thickens fuel, making it harder for the fuel pump to deliver consistently, especially in older vehicles with potentially worn components. This could be due to:
* Fuel pump: A weak fuel pump struggles to maintain pressure when cold. As the fuel warms, it becomes less viscous, alleviating the problem.
* Fuel filter: A clogged fuel filter restricts fuel flow, especially noticeable when cold.
* Fuel injectors: Injectors can leak or become less efficient when cold, leading to an inconsistent fuel/air mixture. They often improve once warmed up.
* EGR valve: A faulty EGR valve can cause rough running, particularly when cold, as the mixture isn't properly controlled. (Exhaust Gas Recirculation)
* Ignition system problems: Similar to fuel delivery, components in the ignition system can perform poorly when cold. This might involve:
* Spark plugs/wires: Worn or fouled spark plugs will misfire more often when cold. Similarly, cracked or worn spark plug wires can fail to transmit the spark reliably until components heat up.
* Distributor cap and rotor (if applicable): These components can crack or develop carbon tracking, causing weak or intermittent sparks when cold. The 1993 Town Car may have a distributor; check your model's specifics.
* Ignition coil: A weak ignition coil might not produce sufficient voltage for consistent spark when cold.
* Other potential issues (less common):
* Mass airflow sensor (MAF): A faulty MAF sensor can provide incorrect air/fuel readings, leading to a rough idle, especially when cold.
* Throttle position sensor (TPS): A faulty TPS can cause incorrect fuel metering, again impacting cold start performance.
* Vacuum leaks: Small vacuum leaks in hoses or the intake manifold can cause rough running. These leaks might be more apparent when the engine is cold, due to differences in pressure and temperature.
Troubleshooting Steps:
To diagnose the problem, a systematic approach is best:
1. Check the obvious: Start by inspecting spark plugs, wires, and the distributor cap and rotor (if equipped). Look for cracks, corrosion, or signs of wear.
2. Listen for unusual sounds: A whining sound from the fuel pump might indicate a problem.
3. Check engine codes: Use an OBD-II scanner (or a code reader for older vehicles) to retrieve any diagnostic trouble codes (DTCs) stored by the engine control module (ECM). These codes can provide valuable clues.
4. Consult a repair manual: A specific repair manual for your 1993 Lincoln Town Car will have detailed diagnostic procedures and specifications.
5. Professional diagnosis: If you're not comfortable performing these checks, take your car to a qualified mechanic. They have the tools and experience to properly diagnose the issue.
The rough running only when cold strongly suggests a problem with fuel delivery or ignition, but a thorough inspection is necessary to pinpoint the exact cause.
