Possible Causes:
* Ignition System:
* Worn Spark Plugs/Wires: These are the most common culprits for rough running. Check for worn electrodes, cracks, or corrosion on the plugs and wires. Replace them if necessary.
* Ignition Coil: A failing ignition coil can cause misfires and rough running. Testing is needed to determine its condition.
* Distributor Cap and Rotor (if equipped): Cracks or corrosion in the distributor cap and rotor can interrupt the spark delivery. Inspect them closely.
* Ignition Control Module (ICM): This module controls the ignition timing. A faulty ICM can lead to erratic engine performance.
* Crankshaft Position Sensor (CKP): This sensor tells the computer the engine's rotational position. A faulty sensor can cause major running issues.
* Fuel System:
* Fuel Injectors: Clogged or faulty fuel injectors can lead to inconsistent fuel delivery, resulting in a rough idle and rough running at all speeds. Cleaning or replacing injectors might be necessary.
* Fuel Filter: A clogged fuel filter restricts fuel flow. Replace it if it's dirty or hasn't been changed recently.
* Fuel Pump: A weak or failing fuel pump might not supply enough fuel pressure. Check fuel pressure with a gauge.
* Air Intake System:
* Mass Airflow Sensor (MAF): A dirty or faulty MAF sensor provides inaccurate readings to the engine computer, leading to poor fuel mixture and rough running. Clean it with MAF sensor cleaner (following instructions carefully) or replace it if necessary.
* Air Filter: A severely clogged air filter restricts airflow, leading to a lean fuel mixture and rough running. Replace it with a new one.
* Vacuum Leaks: Leaks in the vacuum lines can disrupt the engine's operation. Inspect all vacuum lines for cracks or loose connections.
* Engine Mechanical Issues:
* Worn Piston Rings or Valves: This would usually be accompanied by other symptoms like low compression, blue smoke from the exhaust, and loss of power. A compression test is needed.
* Camshaft Issues: Problems with the camshaft can affect valve timing, causing rough running.
Troubleshooting Steps:
1. Check Engine Light: If the check engine light is on, get the codes read using an OBD-II scanner. This will provide valuable clues about the problem.
2. Visual Inspection: Inspect all visible components of the ignition and fuel systems for signs of damage, corrosion, or leaks.
3. Start with the Basics: Replace spark plugs and wires, check the air filter, and ensure all vacuum lines are properly connected.
4. Systematic Approach: Address the most likely causes first (spark plugs, wires, air filter, fuel filter).
5. Professional Help: If you're not comfortable working on your car, take it to a qualified mechanic for diagnosis and repair.
The rough running at all speeds suggests a significant problem. Ignoring it could lead to further damage. A proper diagnosis is crucial to fixing the issue effectively. Remember to always consult your owner's manual for specific information about your vehicle.
