* Crankshaft Position Sensor (CKP): A faulty CKP sensor can lead to misfires, especially on multiple cylinders. It's crucial for determining engine timing and if it's malfunctioning, the ECU might not send the correct signals to fire the spark plugs at the appropriate time. Cylinders 2 and 3 being affected together suggests a commonality in their firing order relative to the sensor.
* Camshaft Position Sensor (CMP): Similar to the CKP sensor, a faulty CMP sensor affects the timing of the valves and can lead to misfires. It's less likely to cause misfires on only two specific cylinders, but it's still a possibility.
* ECU (Engine Control Unit): While less common, a failing ECU could be the culprit. It's responsible for controlling everything, and a faulty unit might send incorrect signals to specific cylinders. This is a less likely scenario, but worth considering if other components check out.
* Wiring Harness Issues (Despite new wires): While you replaced the wires to the plugs, there might be a problem *within* the main engine harness, particularly near the connectors for cylinders 2 and 3. A short or break could be causing intermittent or consistent misfires.
* Fuel Injector Issue (less likely): While less probable given the specific cylinder pattern, a clogged or faulty fuel injector in either cylinder 2 or 3 could cause a misfire, though typically one would expect a continuous misfire, not an intermittent one. If the injectors weren't replaced or tested, it is worth considering.
* Valve Issue (Least Likely): Given your compression test was good, this is a long shot, but a sticking or damaged valve in either cylinder *could* contribute, though again you would expect consistent misfires.
Troubleshooting Steps:
1. Check the CKP and CMP Sensors: These are relatively inexpensive and easy to replace. Inspect them visually for damage and consider replacing them.
2. Inspect the Wiring Harness: Carefully examine the harness leading to cylinders 2 and 3 for any damage, breaks, or shorts, particularly near connectors. You may need a wiring diagram.
3. Perform a Fuel Injector Test (if possible): This involves testing the electrical signal and flow of fuel from each injector. This may require specialized tools.
4. Have the ECU Scanned: Use a professional OBD-II scanner to read any diagnostic trouble codes (DTCs) stored in the ECU. This may pinpoint the problem.
Important Note: The fact that cylinders 2 and 3 are affected *together* strongly suggests a shared component problem, making the CKP sensor a prime suspect. Start with the most likely and cost-effective options before moving to more expensive repairs like the ECU. Always consult a repair manual specific to your 2000 Ford Contour for detailed instructions and diagrams.
