Possible Causes:
* Resonance/Exhaust System Component Vibration: The most likely culprit. At 2000 RPM, a specific frequency of the engine's vibrations might be causing a part of the exhaust system (muffler, pipe, hangers) to vibrate excessively, creating a loud noise. This is amplified if there's any looseness, damage, or wear in the exhaust system. A slightly dented or weakened pipe can act as a resonator at specific frequencies.
* Exhaust Manifold Leak (Less Likely): While less probable given the RPM-specific nature, a crack in the exhaust manifold could cause noise, but it would likely be more pronounced at higher RPMs and possibly accompanied by other symptoms (loss of power, rough running).
* Catalytic Converter Issues (Less Likely): A failing catalytic converter can make noise, but it's usually a rattling sound, not necessarily isolated to a single RPM.
Troubleshooting and Fixes:
1. Visual Inspection: Carefully examine the entire exhaust system from the engine to the tailpipe. Look for:
* Loose or broken hangers: Tighten or replace any loose or broken hangers.
* Dents or rust damage: Significant dents or rust holes can cause resonance. Repair or replace damaged sections.
* Leaks: Look for holes or cracks in the pipes, muffler, or connections.
* Loose or broken heat shields: These can rattle and create noise, but usually not limited to 2000 RPM.
2. Sound Location: With the engine running at 2000 RPM, try to pinpoint the exact location of the noise. This will help you focus your inspection. Have someone rev the engine while you listen carefully.
3. Professional Inspection: If you can't identify the problem visually, take it to a qualified mechanic specializing in exhaust systems. They have the tools and experience to diagnose the issue properly.
4. Test Drive: Before and after any repairs, test drive the vehicle to confirm the noise is gone.
Important Note: Ignoring exhaust problems can lead to further damage and potentially dangerous situations (carbon monoxide poisoning if there's a significant leak). Address this issue promptly.
It's very unlikely that a simple fix like tightening a bolt will solve this; it almost certainly requires finding and repairing a structural problem within the exhaust system. A visual inspection and possibly some hands-on experience by a mechanic are needed.
