Ignition System:
* Worn Spark Plugs and/or Wires: These are the most common and easiest to check. Old, worn, or fouled plugs can misfire, causing a rough idle. Worn wires can lead to poor spark delivery.
* Distributor Cap and Rotor (if applicable): Cracks or corrosion in the cap and rotor can disrupt the spark delivery. This is less likely on later models that may have coil-on-plug ignition.
* Ignition Coil(s): A failing ignition coil can cause misfires in one or more cylinders.
* Crankshaft Position Sensor (CKP): This sensor tells the computer the engine's rotational speed. A faulty sensor can cause erratic idling.
* Cam Position Sensor (CMP): Similar to the CKP, a faulty CMP sensor can disrupt the ignition timing, leading to a rough idle.
Fuel System:
* Dirty Fuel Injectors: Clogged injectors prevent proper fuel delivery to the cylinders.
* Fuel Pressure Regulator: A faulty regulator can cause incorrect fuel pressure, leading to a lean or rich fuel mixture.
* Fuel Filter: A clogged fuel filter restricts fuel flow.
* Mass Airflow Sensor (MAF): This sensor measures the amount of air entering the engine. A dirty or faulty MAF sensor can provide incorrect readings, leading to a poor air/fuel mixture.
* Throttle Position Sensor (TPS): This sensor tells the computer the throttle position. A faulty TPS can cause erratic idling.
Vacuum Leaks:
* Vacuum Hoses: Cracked, loose, or disconnected vacuum hoses can disrupt the engine's vacuum system, affecting idle. Inspect all vacuum hoses carefully.
* Intake Manifold Gasket: A leak in this gasket can also lead to vacuum problems.
Other Potential Causes:
* EGR Valve: A faulty exhaust gas recirculation valve can cause rough idling.
* PCV Valve: A problem with the positive crankcase ventilation valve can lead to excessive crankcase pressure and rough running.
* Engine Mounts: Worn engine mounts can allow excessive engine movement, leading to vibrations and a rough idle.
* Low Engine Compression: This indicates a problem with the cylinders, valves, or piston rings.
Troubleshooting Steps:
1. Check the basics: Start with the easy things – inspect spark plugs and wires, check for obvious vacuum leaks, and ensure all connections are secure.
2. Read trouble codes (if equipped): Use an OBD-II scanner to read any diagnostic trouble codes stored in the car's computer. This can point you in the right direction. Remember that a 1994 model may not be fully OBD-II compliant.
3. Check fuel pressure: A fuel pressure gauge can determine if the fuel pressure is within specification.
4. Consult a repair manual: A repair manual specific to your 1994 Chrysler LHS will provide detailed diagnostic procedures and specifications.
It's important to systematically check these potential problems. If you're not comfortable working on your car, take it to a qualified mechanic for diagnosis and repair. Attempting repairs without the proper knowledge can lead to further damage.
