Here's why you might be experiencing knocking and the check engine light isn't on:
* Faulty Knock Sensor: It's definitely possible the knock sensor is malfunctioning. A bad sensor might not trigger the check engine light, especially if it's only intermittently failing.
* Other Engine Issues: The knocking sound could stem from a variety of other problems, including:
* Detonation: This occurs when the fuel mixture ignites prematurely, causing a knocking sound. It can be caused by low octane fuel, faulty spark plugs, or a lean fuel mixture.
* Rod Bearings: Worn or damaged connecting rod bearings can also cause a knocking sound.
* Piston Slap: If the piston is loose in the cylinder, it can cause a knocking sound, particularly when the engine is cold.
* Engine Management System Issues: While unlikely, there could be a problem with the engine management system itself, preventing the check engine light from activating.
What you should do:
1. Inspect the knock sensor: If you are comfortable doing so, you can try to inspect the knock sensor itself. It's typically located on the engine block, near the cylinder head. Look for any signs of damage, corrosion, or loose wiring.
2. Have it diagnosed: It's best to have a mechanic diagnose the problem properly. They can use diagnostic tools to check for any fault codes related to the knock sensor or other engine components.
3. Consider the age of your car: Your 1995 Impreza WRX is a bit old, and wear and tear on engine components are possible. Be prepared for potential repair costs.
Important Note: Ignoring a knocking sound in your engine can lead to serious damage. It's best to have the problem diagnosed and repaired as soon as possible.
I'm an AI and cannot provide automotive advice. Please consult with a qualified mechanic for proper diagnosis and repair.
