1. Wiring and Connections:
* Injector Harness: Carefully inspect the wiring harness going to injector #2 for any breaks, chafing, corrosion, or loose connections. A seemingly minor issue in the harness can cause intermittent or complete failure.
* Coil Pack Wiring: Double-check the wiring to the coil pack (even though you replaced it, a wiring problem could still exist). Ensure proper seating and look for any damage.
* Grounds: Poor grounds can disrupt electrical signals. Trace the ground wires from the engine to the chassis and ensure they are clean and securely connected.
2. Mechanical Issues (Less Likely, but Possible):
* Valve Problem: Though less likely after replacing the cam position sensor, a bent or sticking valve in cylinder #2 could cause a misfire. A compression test will help diagnose this. Low compression in cylinder #2 compared to others points to a mechanical problem.
* Piston/Ring Problems: Worn piston rings or a damaged piston could cause a misfire, though this is less likely unless the engine has significant wear. Again, a compression test is necessary.
* Intake Air Leak: A vacuum leak before the throttle body, specifically on the intake manifold runner for cylinder #2, can cause a lean condition leading to misfire. Inspect intake manifold gaskets and boots carefully, especially if you've recently done any work around this area.
3. Further Diagnostic Steps:
* Data Stream Analysis: Use a scan tool capable of live data to monitor various engine parameters while the engine is running. Look for things like:
* Fuel Injector Pulse Width: Is the injector for cylinder #2 pulsing correctly?
* Short Term and Long Term Fuel Trims: These can indicate a lean condition (possible vacuum leak) or rich condition.
* Oxygen Sensor Readings: Check if the oxygen sensor is showing a problem related to cylinder #2.
* Misfire Counts: Keep an eye on the misfire count for cylinder #2 to see if the frequency changes with RPM or load.
* Compression Test: As mentioned before, this is crucial to rule out mechanical problems within the cylinder.
* Cylinder Leak-Down Test: This is a more precise test than a compression test, allowing you to identify exactly where the compression is escaping (valves, piston rings, etc.).
Important Note: Before diving into extensive mechanical inspections, thoroughly re-examine your electrical system (wiring and grounds) as the simplest solution is often overlooked. The intermittent nature sometimes associated with misfires makes a thorough inspection of all connections highly advisable. If you're not comfortable performing these tests, take your vehicle to a qualified mechanic for proper diagnosis and repair.
