* Ignition System:
* Worn Spark Plugs or Wires: This is a common culprit. Worn plugs can misfire, leading to sputtering and knocking. Worn wires can prevent a consistent spark.
* Failing Ignition Coil(s): The coil provides the high voltage for the spark plugs. A weak or failing coil will cause misfires, especially under load.
* Distributor Cap and Rotor (if equipped): Older vehicles might have a distributor; worn contacts here can disrupt the spark delivery.
* Fuel System:
* Clogged Fuel Filter: A clogged filter restricts fuel flow, especially when the engine demands more fuel at higher speeds.
* Low Fuel Pressure: A failing fuel pump or regulator can't supply enough fuel under high demand.
* Dirty or Failing Fuel Injectors: Clogged injectors deliver an inconsistent fuel spray, leading to misfires and rough running.
* Bad Mass Airflow Sensor (MAF): This sensor measures the amount of air entering the engine. A faulty MAF provides inaccurate readings, leading to a poor air/fuel mixture.
* Engine Mechanical Issues:
* Low Compression: Worn piston rings or valves can cause low compression, leading to knocking and sputtering. This is a more serious issue.
* Connecting Rod Bearing Issues: Knocking can also be a sign of worn connecting rod bearings, a serious problem requiring immediate attention. This is more likely to be a consistent knock rather than one that only appears under load.
* Valvetrain Problems: Worn or damaged valves can cause misfires and knocking.
* Other Possibilities:
* Vacuum Leaks: Leaks in the intake system can disrupt the air/fuel mixture.
* EGR Valve Problems: A faulty Exhaust Gas Recirculation valve can cause rough running.
Troubleshooting Steps (in order of easiest/cheapest to most difficult/expensive):
1. Check the basics: Start with the easiest and cheapest fixes: Check the spark plugs and wires for wear. Inspect the air filter; replace if dirty. Ensure the fuel level is adequate.
2. Listen carefully: Is the knock a rhythmic "pinging" (often detonation due to improper fuel/air mixture or timing), a more constant metallic knock (potential bearing issue), or a random misfire-like sound? The sound can help narrow down the possibilities.
3. Check codes: Use an OBD-II scanner to check for trouble codes. These codes can point you towards specific problem areas.
4. Professional Diagnosis: If you're not comfortable diagnosing the problem yourself, take your Stratus to a qualified mechanic. They have the tools and experience to diagnose the problem accurately.
Ignoring the problem could lead to more severe engine damage. The knocking, especially under load, suggests a significant issue that needs prompt attention to prevent further harm.
