The catalyst must be at operating temperature and requires precise engine fuel and ignition system management for the chemical change to occur. A converter can fail from engine misfires, running too rich (too much fuel), oil burning, coolant leaks, physical damage, or catalytic converter theft. Common symptoms include a Check Engine Light, rotten egg smell, rattles, or low power. This perspective reflects Jerry’ experience helping over 40,000 customers access accurate repair prices, and this guide can help you get at root causes. You can then use Jerry’s tools to sort out repairs at a reasonable price.
In this guide, you’ll learn:
- What’s urgent and what can wait
- Common causes and fixes
- Typical catalytic converter repair costs
- When to call a pro
- Test numbers to help avoid misdiagnosis and extra costs
The Jerry app provides repair estimates from a national database, finds shops near you (no phone calls), shows open recalls, lets you chat with AI about symptoms, and sets maintenance reminders. Download the Jerry app to check likely repair costs and compare nearby shops in minutes to help you get your car in top shape with as little hassle as possible.
Real customers Jerry helped
While pricing can vary based on different factors like location, parts used, and exact vehicle, Jerry uses real customer experiences to show what drivers are paying right now. Here are some examples of customers we’ve helped:
Estimates are modeled based on real vehicle and location data; names have been changed. Actual prices will vary by shop, parts, and vehicle condition.
At-a-glance: Can I keep driving?
Match your situation to the right risk level. Jerry customers are using these buckets to gauge their situations:
- 🚨 Urgent—turn it off and get help now.
- Strong rotten egg smell, engine misfiring, or a glowing red converter.
- Severe loss of power or stalling at speed (possible clogged cat).
- Loud exhaust after suspected theft (unsafe and illegal to drive).
- Smoke or burning smell under the car (overheating exhaust parts).
- Blinking check engine light.
- 🕒 Soon—okay to drive, fix this week.
- Check Engine Light is on, but not blinking.
- Rattling from under the car on startup or bumps.
- Failed emissions test for catalyst monitor only.
- ✅ Monitor—safe to drive.
- Slight MPG drop in cold weather with no codes.
- Brief egg smell after hard acceleration that goes away.
Why it matters: heat and backpressure from a failing cat rise quickly. Heat damages oxygen sensors, wiring, and floor insulation, while backpressure can cause engine stumbling or stalling.
Symptoms
Different problems with catalytic converters show up in different ways. Here’s how Jerry customers are finding that symptoms usually line up with causes and fixes:
Note: California Air Resources Board (CARB) states (CA, NY, CO, ME) require CARB-approved converters that cost more. Hybrids are frequent theft targets; EVs don’t have cats.
Risks if you ignore it
Jerry customers find that leaving a bad catalytic converter unfixed comes with real dangers, including:
Fire hazard: an overheated cat can glow red and ignite nearby parts. A potential fire hazard is a risk not worth taking for your own or other drivers’ safety, not to mention damage to the vehicle. A typical case involves the driver parking the car over something flammable, potentially starting a fire.
Engine damage: clogged cats increase exhaust backpressure, potentially damaging exhaust valves. Engine operation will be sluggish because of high exhaust backpressure.
Sensor/wiring damage: heat kills O2 sensors and melts wiring that’s bundled together and fairly close to the catalytic converter. A few precautions here will save having to unnecessarily replace O2 sensors and troubleshoot issues caused by melted wiring.
Emissions/legality: inspection failures and potential fines may result from neglecting catalytic converter repairs. You’ll have the added cost and inconvenience of addressing the underlying reasons why the car didn’t pass the smog test and the hassle of a retest.
Higher costs: a cheap misfire repair can turn into a $2,000+ cat replacement if ignored. A delayed repair can escalate costs quickly if other car components are impacted.
Can I do this repair myself? (DIY vs. pro)
Here’s a breakdown of what you can check safely yourself and what’s better left to a professional. Use Jerry’s insights into parts and labor rates to make an informed decision as you go:
DIY (safe checks)
- Inspect for exhaust leaks before upstream O2 sensors.
- Listen for rattles under the car (engine off, cold).
- Check spark plugs, coils, or recent bad fuel that may cause misfires.
- Stop driving if you smell rotten eggs or see a glowing cat.
Pro (recommended)
- Analyze fuel trims and misfire data (LTFT, STFT).
- Compare upstream vs downstream O2 sensor patterns.
- Test for backpressure (<1.5 psi normal at 2,500 rpm).
- Use an IR thermometer (outlet should be ~100–200°F hotter than inlet).
- Run vacuum tests for restrictions.
- Replace with the correct EPA/CARB-approved converter with new gaskets/hardware.
- Perform a drive cycle to reset monitors and confirm repair.
Special notes:
- Federal emissions warranty covers cats for 8 yrs/80k miles on many vehicles.
- CARB states require approved cats with EO labels.
- Aftermarket high-flow cats can cause codes and may be illegal.
- Rusted studs and seized O2 sensors can add labor costs.
What NOT to do
Some “fixes” make things worse, illegal, or dangerous. Avoid these:
- ❌ Don’t hollow out or bypass the cat, which is illegal and unsafe.
- ❌ Don’t keep driving with an active misfire, which can destroy the cat in minutes.
- ❌ Avoid damaging wiring, fuel lines and sensors when welding, use precautions. Temporarily remove sensors and either shield or temporarily move or remove any wiring. O2 sensors are a primary concern, since they’re screwed into the exhaust pipe close to the catalytic converter.
Prevention
Jerry customers prevent most catalytic converter issues with a few proactive habits:
Fix misfires immediately at a trusted shop.
Replace spark plugs on schedule (60k–100k miles).
Repair engine oil and coolant leaks promptly. This is just good housekeeping, and they’ll need repair eventually anyway.
Use only higher quality gasoline. It might be a false economy in the general operation of the car to use poor quality gasoline. Saving a few cents now isn’t worth costly fixes longer term.
Keep the cooling system in good shape. Repair any coolant leaks right away and replace coolant according to manufacturer’s recommendations.
Drive highway speeds for 15–20 minutes weekly to keep the cat clean.
Protect against theft with VIN etching, shields, or parking strategies. Catalytic converters contain precious metals like platinum, palladium and rhodium, making them attractive to thieves. Park your car in a garage overnight and in areas that have good traffic so there’s no time to steal the catalytic converter without someone seeing the act.
Use the Jerry app to check for emissions recalls and set maintenance reminders. The app can also help you find local quotes at trusted shops for routine maintenance and more significant repairs to maximize your dollar.
What our customers are asking us
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Is it safe to drive with a bad catalytic converter?
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What is the catalytic converter replacement cost?
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Are catalytic converters covered by warranty or recalls?
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Do cat cleaners work?
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How can I tell if my cat was stolen?
Steve Kaleff began working on cars at the very young age of nine years old, when his dad actually let him make fixes on the family car. Fast forward to the beginning of a professional career working at independent repair shops and then transitioning to new car dealerships. His experience was with Mercedes-Benz, where Steve was a technician for ten years, four of those years solving problems that no one could or wanted to fix. He moved up to shop foreman and then service manager for 15 years. There have been tremendous changes in automotive technology since Steve started his professional career, so here’s looking forward to an electric future!
Nick Wilson is an editor, writer, and instructor across various subjects. His past experience includes writing and editorial projects in technical, popular, and academic settings, and he has taught humanities courses to countless students in the college classroom. In his free time, he pursues academic research, works on his own writing projects, and enjoys the ordered chaos of life with his wife and kids.
