Ignition System:
* Spark Plug: This is the most frequent cause. A fouled, worn, damaged, or incorrectly gapped spark plug will prevent proper ignition. Check the plug for wear, fouling (black, oily, or white deposits), or damage.
* Spark Plug Wire: A cracked, worn, or loose spark plug wire can prevent the spark from reaching the plug effectively. Inspect for damage and ensure it's securely connected.
* Ignition Coil: The ignition coil provides the high voltage for the spark plug. A faulty coil will result in a weak or no spark. A coil pack test is usually needed to confirm this.
* Ignition Control Module (ICM): This module controls the ignition coils. A failing ICM can cause intermittent or complete misfires in one or more cylinders.
Fuel System:
* Fuel Injector: A clogged or faulty injector in cylinder one won't deliver the proper amount of fuel. A fuel injector cleaning or replacement may be necessary.
* Fuel Pressure: Low fuel pressure can affect all cylinders, but a particularly weak injector might only show a problem in one cylinder under load. A fuel pressure test is needed.
Engine Mechanical Issues:
* Valve Problem: A burnt, bent, or sticking valve in cylinder one will prevent proper combustion. This is less likely than ignition or fuel issues but needs to be considered. A compression test is needed to check for this.
* Piston/Rings: Severe wear or damage to the piston or piston rings can lead to low compression and misfires. Again, a compression test will reveal this.
* Damaged Rocker Arm: A damaged rocker arm won't allow the valve to open and close correctly, inhibiting combustion.
Other Possibilities:
* Vacuum Leaks: A significant vacuum leak can disrupt the air/fuel mixture, affecting one or more cylinders.
* Crankshaft Position Sensor (CKP Sensor): A faulty CKP sensor can cause misfires by providing incorrect timing information to the engine control module (ECM).
* ECM Issues: While less common, a malfunctioning ECM can cause misfires. This is usually diagnosed by a mechanic.
Troubleshooting Steps:
1. Check for Diagnostic Trouble Codes (DTCs): Use an OBD-II scanner to read any stored trouble codes. These codes will often point directly to the problem.
2. Inspect Spark Plug and Wire: Start with the simplest and cheapest checks.
3. Visual Inspection: Look for any obvious signs of damage or leaks around cylinder one.
4. Compression Test: This is crucial for ruling out mechanical issues.
5. Fuel Pressure Test: Check fuel pressure to ensure the injectors are getting adequate fuel.
It's important to diagnose the problem systematically. Starting with the most likely and easily checked components (spark plug, wire, etc.) is recommended. If you're not comfortable performing these checks yourself, take your Cavalier to a qualified mechanic for proper diagnosis and repair.
