By the Marlow Automotive service team · Reviewed by our exhaust technicians · Updated July 2026. Exhaust repair on all makes and models at our Plano shop since 2002.
The short answer: a new rumble, tick, or drone from underneath, a rotten-egg smell, falling fuel economy, or a check engine light with a P0420 code all point at the exhaust system — and the earlier it's inspected, the cheaper the fix. Exhaust problems are unusual in one respect: small leaks are inexpensive to repair, but the parts they damage downstream (oxygen sensors, catalytic converters) are some of the priciest on the car.
What does the exhaust system actually do?
It routes hot exhaust gases safely out the back, quiets the engine, and — in the catalytic converter — chemically scrubs the pollutants. Every joint from the exhaust manifold to the tailpipe is a potential leak point, and each one lives through extreme heat cycles every single drive.
The warning signs, in order of urgency
- Exhaust smell in the cabin — stop driving and get it checked immediately. Carbon monoxide is odorless and rides along with the gases you can smell.
- Ticking on cold start that fades as the engine warms — classic manifold leak or cracked flex pipe expanding shut with heat.
- Rotten-egg (sulfur) smell — the catalytic converter isn't finishing its chemistry: either it's failing, or an engine problem is overloading it.
- Louder exhaust note, drone at highway speed, rattling underneath — leaks, failed hangers, or a loose heat shield. Cheap now, expensive later.
- Check engine light P0420/P0430 — "catalyst efficiency below threshold." Get the free code scan before assuming the worst: sometimes it's an oxygen sensor, not the converter.
The failure mode that costs real money
A catalytic converter almost never fails on its own — it gets killed by an upstream problem: a misfire dumping raw fuel, an oil-burning engine, or a coolant leak. Replacing a converter without fixing the root cause means buying a second converter within the year. That's why our exhaust diagnostics always start upstream; it's also why a flashing check engine light is a stop-driving-now event (see what a complete diagnostic includes).
What honest exhaust repair looks like
On the lift, the whole system gets inspected end to end — photographed, so you see the actual crack, rusted flange, or failed hanger before approving anything. Where a section can be repaired instead of replaced, we say so. Exhaust work at Marlow Automotive is backed by at least our standard 12-month/12,000-mile warranty, with 2 years / 24,000 miles on qualifying repairs — and our 4.9-star Google reviews are full of drivers who came in expecting a big bill and left with a small one.
What to do next
If your car is louder than it was last month, or you've smelled anything unusual, have it looked at this week — most exhaust repairs are same-day. Book online, call 972-633-1299, or see our auto exhaust services.