1. The Easy Checks (Do these FIRST):
* Spark Plug and Wire: Inspect the spark plug for cylinder 1. Is it fouled (black, wet, oily)? Is it damaged? Check the spark plug wire for cracks, fraying, or damage where it connects to both the plug and the distributor cap (if applicable, some Aleros have coil-on-plug). Replace if necessary.
* Ignition Coil (Coil-on-Plug or Distributor): If your Alero uses coil-on-plug ignition, inspect the coil for cylinder 1 for any signs of damage. If it uses a distributor, check the cap and rotor for cracks, burns, or corrosion. A faulty coil or distributor components can prevent spark delivery.
* Fuel Injector: Check for fuel delivery to cylinder 1. This is more complex and might require a fuel pressure test or injector diagnostic using a scan tool. A clogged or faulty injector won't provide fuel to the cylinder.
* Vacuum Leaks: Inspect vacuum lines for cracks or disconnections. A significant leak can disrupt air/fuel mixture, leading to misfires.
2. More Advanced Diagnostics:
* Compression Test: This is crucial. Low compression in cylinder 1 indicates a problem with the engine itself (worn piston rings, valves, head gasket).
* Scan Tool: A scan tool can read diagnostic trouble codes (DTCs). These codes can pinpoint the likely cause of the misfire, such as a specific sensor malfunction. Auto parts stores often offer free code reading.
* Injector Pulse Test: This test verifies that the injector is receiving the electrical signal to open and inject fuel. Requires a scan tool or multimeter.
* Camshaft Position Sensor (CMP) and Crankshaft Position Sensor (CKP): These sensors are vital for proper ignition timing. Faulty sensors can lead to misfires. They're commonly replaced in older cars.
3. Possible Causes Based on Symptoms:
* Worn Spark Plug: The most common cause of a single cylinder misfire.
* Faulty Ignition Coil: Coil-on-plug systems are prone to failure.
* Clogged Fuel Injector: Less common, but can happen.
* Vacuum Leak: Disrupts air/fuel mixture.
* Internal Engine Problems: Low compression points to issues like worn rings or valves.
* Sensor Malfunction: Various sensors (CMP, CKP, MAF, etc.) can cause misfires.
Important Considerations:
* Safety First: Work on a car requires safety precautions. Disconnect the negative battery terminal before working on electrical components.
* Professional Help: If you're not comfortable performing these checks yourself, take your car to a qualified mechanic. Misdiagnosis can lead to unnecessary repairs or further damage.
Start with the simple checks. If those don't solve the problem, move on to the more advanced diagnostics or seek professional help. Remember to note down your findings at each step to help you (and a mechanic) pinpoint the issue.
