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Idaho Exhaust & Muffler Laws (2026)

Info: Your vehicle needs a muffler in good order, and cutouts and bypasses (which route exhaust around the muffler) are banned, along with changes that make the exhaust louder — in Idaho, "excessive noise" means more than 92 decibels measured at 20 feet (Idaho Code §§ 49-937, 49-106).

InfoVerified Jun 19, 2026

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Official source: legislature.idaho.gov →

General legal information, not legal advice — verify important decisions with a licensed attorney.

Exhaust & Muffler in states bordering Idaho

The same rule in each neighboring state LawLert has verified, from that state’s own official source.

MontanaInfo
Your vehicle needs a muffler in good working order that prevents excessive noise and smoke, and muffler cutouts and bypasses (which route exhaust around the muffler) are prohibited. Montana sets no fixed decibel limit (Mont. Code Ann. § 61-9-403).
Verified Jun 19, 2026 · Source: mca.legmt.gov · Full Montana rule →
NevadaInfo
Your vehicle needs a muffler in good working order that meets the Department's rules, and cutouts and bypasses (which route exhaust around the muffler) are banned on the highway. No fixed decibel limit is confirmed (NRS § 484D.415).
Verified Jun 19, 2026 · Source: leg.state.nv.us · Full Nevada rule →
OregonInfo
Your vehicle needs a proper exhaust. On the Department of Environmental Quality's stationary test, passenger cars built in 1976 or later are capped at 88 decibels, and cars built before 1976 at 92 decibels, measured at 25 feet (Or. Rev. Stat. § 815.250).
Verified Jun 19, 2026 · Source: oregonlegislature.gov · Full Oregon rule →
UtahInfo
Your vehicle needs a muffler or other effective noise-suppressing system in good working order, and a cut-out, bypass or similar device (which routes exhaust around the muffler) is prohibited. Utah sets no fixed decibel limit (Utah Code § 41-6a-1626).
Verified Jun 19, 2026 · Source: le.utah.gov · Full Utah rule →
WashingtonInfo
Your vehicle needs a muffler in good working order, cutouts and bypasses (which route exhaust around the muffler) are prohibited, and so is exhaust amplified beyond the factory muffler. Washington sets no decibel limit in statute (RCW § 46.37.390).
Verified Jun 19, 2026 · Source: app.leg.wa.gov · Full Washington rule →
WyomingInfo
Your vehicle needs a muffler or other effective noise-suppressing system in good working order, and a cut-out, bypass or similar device (which routes exhaust around the muffler) is prohibited. Wyoming sets no fixed decibel limit (Wyo. Stat. § 31-5-953).
Verified Jul 22, 2026 · Source: wyoleg.gov · Full Wyoming rule →

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