* Faulty CMP Sensor Signal: While unlikely to cause *better* running without the sensor, a faulty CMP sensor might be sending a *bad* signal that's causing the rough running. The PCM (Powertrain Control Module) might be trying to compensate for bad data, leading to a rough idle and poor performance. A simple check would be to replace the CMP sensor.
* Worn or Damaged Camshaft: If the camshaft lobes are significantly worn, the sensor might be picking up inconsistent signals, causing the rough running. The engine might run better without the sensor because the PCM defaults to a rudimentary timing strategy, ignoring the faulty sensor data.
* PCM Issue: A faulty PCM is also a possibility. It might be misinterpreting the signal from the CMP sensor or have a problem with its internal timing calculations. A scan tool capable of reading PCM codes could reveal this.
* Wiring Problem: While you say it's reconnected, there might be a short or intermittent connection in the wiring harness to or from the CMP sensor. A broken or frayed wire could send spurious signals when connected. Carefully inspect the wiring.
* Crankshaft Position Sensor (CKP) Issue: The engine also uses a crankshaft position sensor. If the CKP is malfunctioning, the PCM might struggle to sync the engine timing, especially with a faulty or missing CMP signal. A faulty CKP would likely make the engine run poorly *with* or *without* the CMP sensor.
* Other Sensor Issues: Other sensors like the MAP (Manifold Absolute Pressure) sensor or the throttle position sensor could contribute to the problem, especially when combined with a faulty CMP sensor signal.
Troubleshooting Steps:
1. Replace the CMP Sensor: This is the simplest and most likely solution. A cheap sensor can cause a world of problems.
2. Inspect the Wiring: Carefully check the wiring harness from the CMP sensor to the PCM for breaks, shorts, or corrosion.
3. Check for Diagnostic Trouble Codes (DTCs): Use an OBD-II scanner to read the PCM's trouble codes. This will give you valuable clues to the underlying problem.
4. Inspect the Camshaft: If the problem persists, a mechanic might need to inspect the camshaft for wear.
5. Consider the PCM: If all else fails, PCM problems can be difficult to diagnose and may require professional help.
In short, the engine running better without the CMP sensor is a clue pointing to a malfunctioning CMP sensor or a problem the PCM is trying to compensate for based on the sensor's incorrect input. Thoroughly check the sensor, wiring, and codes before moving on to more extensive diagnostics.
