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Iowa Exhaust & Muffler Laws (2026)

Info: Your vehicle needs a muffler in good working order so it doesn't make excessive or unusual noise, and muffler cutouts and bypasses (which route exhaust around the muffler) are prohibited.

InfoVerified Jun 19, 2026

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Your vehicle needs a muffler in good working order so it doesn't make excessive or unusual noise, and muffler cutouts and bypasses (which route exhaust around the muffler) are prohibited. Iowa sets no fixed decibel limit (Iowa Code § 321.436).

Official source: legis.iowa.gov →

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

Exhaust & Muffler in states bordering Iowa

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

IllinoisInfo
Your vehicle needs an adequate muffler and exhaust so it doesn't make excessive or unusual noise, and cutouts and bypasses (which route exhaust around the muffler) are prohibited, as are changes that increase noise. Illinois sets no fixed decibel limit (625 ILCS 5/12-602).
Verified Jun 19, 2026 · Source: ilga.gov · Full Illinois rule →
MinnesotaInfo
Your vehicle needs a muffler in good working order so it doesn't make excessive or unusual noise, and muffler cutouts, bypasses (which route exhaust around the muffler), and similar devices are banned. Minnesota sets no decibel limit in statute (Minn. Stat. § 169.69).
Verified Jun 19, 2026 · Source: revisor.mn.gov · Full Minnesota rule →
MissouriInfo
Your vehicle needs a properly attached muffler to quiet the exhaust, and muffler cutouts and excessive noise are barred — a violation is an infraction. Missouri sets no fixed decibel limit (Mo. Rev. Stat. § 307.170).
Verified Jun 19, 2026 · Source: revisor.mo.gov · Full Missouri rule →
NebraskaInfo
Your vehicle needs a muffler or other noise-suppressing system in good working order, cutouts and bypasses (which route exhaust around the muffler) are unlawful, and changes that increase noise are banned. Nebraska sets no fixed decibel limit (Neb. Rev. Stat. § 60-6,286).
Verified Jun 19, 2026 · Source: nebraskalegislature.gov · Full Nebraska rule →
South DakotaInfo
Your vehicle needs an exhaust system and muffler in good working order, the exhaust has to discharge to the rear or the side, and muffler cut-outs (which route exhaust around the muffler) are prohibited. South Dakota sets no fixed decibel limit (SDCL § 32-15-17).
Verified Jun 19, 2026 · Source: sdlegislature.gov · Full South Dakota rule →
WisconsinInfo
Your vehicle needs an adequate muffler operating at all times, and cutouts and bypasses (which route exhaust around the muffler) are prohibited, along with changes that amplify noise beyond the factory muffler. Wisconsin sets no fixed decibel limit (Wis. Stat. § 347.39).
Verified Jun 19, 2026 · Source: docs.legis.wisconsin.gov · Full Wisconsin rule →

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