* Worn or damaged spark plug wires: Even a new plug won't fire correctly if the wire leading to it is cracked, frayed, or poorly connected. Inspect the wire visually and check the connection at both ends.
* Faulty ignition coil: The ignition coil provides the high voltage needed to fire the spark plug. A failing coil for cylinder #2 will prevent or weaken the spark, causing a misfire. This is a common culprit.
* Ignition control module (ICM) or ECU issue: These components control the firing of the ignition coils. A problem with either could selectively affect cylinder #2.
* Low compression: A low compression reading in cylinder #2 indicates a problem with the piston rings, valves, or head gasket. The spark plug might fire, but insufficient compression prevents proper combustion. A compression test is needed here.
* Fuel injector problem: A clogged or faulty fuel injector for cylinder #2 would prevent fuel from reaching the combustion chamber.
* Vacuum leak: A vacuum leak in the intake manifold can affect the air/fuel mixture, leading to a misfire.
* Damaged valve: A bent or sticking valve in cylinder #2 will also lead to misfires.
* Incorrect plug gap: Although you changed the plug, make sure the gap is correct according to your vehicle's specifications. Too wide or too narrow a gap can cause misfires.
* Wiring harness problem: A damaged or corroded wire in the harness leading to the cylinder #2 components can disrupt the electrical signal.
Troubleshooting Steps:
1. Visual inspection: Carefully examine the spark plug wire, ignition coil, and connections for any visible damage.
2. Check spark: Use a spark tester to verify that a strong spark is reaching the spark plug.
3. Compression test: Measure the compression in cylinder #2 to rule out mechanical issues.
4. Fuel injector test: Test the fuel injector for proper operation. This usually requires a fuel pressure gauge and potentially a scan tool.
5. Vacuum test: Check for vacuum leaks in the intake manifold.
6. Scan tool diagnosis: Use a scan tool to read diagnostic trouble codes (DTCs). The code might pinpoint the specific problem.
If you're not comfortable performing these checks yourself, take your vehicle to a qualified mechanic for diagnosis and repair. Ignoring a misfire can cause engine damage.
