* Ignition System: Worn spark plugs, plug wires, distributor cap, or rotor could cause a misfire leading to rough idling. The ticking could be a symptom of a failing component arcing. This is a relatively common and inexpensive place to start checking.
* Fuel System: A clogged fuel filter, failing fuel pump, or dirty fuel injectors can all disrupt the fuel delivery to the engine, resulting in rough running. This wouldn't typically cause a ticking sound, but other issues in the fuel system could.
* Vacuum Leaks: Cracks in vacuum hoses or a failing vacuum-operated component can disrupt the engine's air/fuel mixture, leading to rough idling. A ticking might be a symptom of air leaking past a vacuum component.
* Valvetrain Issues: A ticking sound is often associated with valvetrain problems like worn rocker arms, lifters (hydraulic or mechanical), or even a sticking valve. These are more likely to be audible throughout the RPM range, but might be more noticeable at idle. This is a more serious issue requiring a more involved diagnosis and repair.
* Sensors: Various sensors (e.g., crankshaft position sensor, mass airflow sensor) can malfunction and cause rough idling. A failing sensor usually doesn't produce a ticking noise.
* Engine Mounts: While less likely to be a primary cause of the rough idle, worn engine mounts could contribute to vibration felt as a rough idle. This wouldn't cause a ticking sound, though.
What to do:
1. Check the basics: Start by inspecting the easily accessible parts: spark plugs, wires, distributor cap and rotor (if equipped). Look for any visible damage, wear, or carbon buildup.
2. Listen carefully to the ticking: Try to pinpoint the location of the ticking sound. Is it coming from the top of the engine (valvetrain area), the bottom (possibly a bearing), or elsewhere? This can help narrow down the possibilities.
3. Check for vacuum leaks: Visually inspect all visible vacuum hoses for cracks or looseness.
4. Consult a mechanic: Given the age of the vehicle and the combination of symptoms, it's highly recommended to have a qualified mechanic diagnose the problem. A proper diagnosis often requires specialized tools and experience. They can perform compression tests and other diagnostic procedures to identify the root cause.
Ignoring the problem could lead to more serious and expensive engine damage. Get it checked out soon.
