High-Probability Causes:
* Ignition Coil(s): The 2.2L often uses multiple ignition coils (one per cylinder or a coil pack). A failing coil will cause a misfire in the cylinder(s) it controls. This is a very common cause of misfires that are present across the RPM range. Inspect the coils visually for cracks or damage. Testing with a multimeter (or better yet, an oscilloscope) is ideal to confirm if a coil isn't producing sufficient voltage.
* Ignition Control Module (ICM): This module controls the firing of the coils. A failing ICM can cause intermittent or consistent misfires across multiple cylinders.
* Crankshaft Position Sensor (CKP): This sensor tells the ECM the position of the crankshaft, crucial for precise ignition timing. A faulty CKP sensor can lead to erratic ignition timing and misfires. This is more likely to cause issues across the RPM range.
* Mass Airflow Sensor (MAF): A dirty or faulty MAF sensor provides inaccurate readings of air intake, leading to a poor air/fuel mixture. While often causing issues at higher RPMs, a severely faulty MAF can affect the whole range. Clean it first, and if the problem persists, consider replacement.
Medium-Probability Causes:
* Injectors: A clogged or faulty fuel injector can prevent proper fuel delivery to a cylinder, causing a misfire. This is more likely to cause a rough idle or misfire at lower loads. Testing injectors requires specialized equipment.
* PCV Valve: A clogged Positive Crankcase Ventilation valve can cause a buildup of pressure in the crankcase, affecting combustion and leading to misfires. This is a relatively cheap part to replace.
Low-Probability Causes (but worth considering if the above are ruled out):
* Compression Issues: Low compression in one or more cylinders can cause misfires. This requires a compression test.
* Head Gasket Leak: A leak in the head gasket can allow coolant or combustion gases to mix, affecting compression and causing misfires.
Troubleshooting Steps:
1. Visual Inspection: Thoroughly inspect all ignition components (coils, wires, distributor cap and rotor if applicable). Look for cracks, burns, corrosion, or loose connections.
2. Code Scan: Use an OBD-II scanner to retrieve any diagnostic trouble codes (DTCs). These codes can pinpoint the problem area.
3. Check for Vacuum Leaks: Inspect all vacuum hoses for cracks or leaks.
4. Test the Components: As mentioned, testing the ignition coils, CKP sensor, and MAF sensor is highly recommended. This often requires a multimeter or specialized scan tool.
5. Compression Test: If other causes are ruled out, a compression test will help determine if there's a mechanical issue within the engine.
Important Note: Working on ignition systems involves high voltage. Disconnect the negative battery terminal before starting any work to prevent injury. If you are not comfortable performing these tests or repairs yourself, take your Cavalier to a qualified mechanic.
