Strong persistent exhaust smell in 2003 Camry two weeks after front catalytic converter replaced

This summer we had the rear catalytic converter replaced in our 2003 Camry. On December 4 we had the front one replaced along with the upstream and downstream O2 sensors. Immediately after we picked up the car two weeks ago we noticed a strong exhaust/burning smell. A day later the check enging light came on. So we brought it back in and our mechanic explained the smell as coming from the coating the manufacturer puts on the converter to keep it from rusting. He said it should burn off after a while, but he agreed the smell was very strong and said that he’d take a look.

They had the car for a day, said they tried to “burn off” some of the coating which appeared to be pretty think, but couldn’t figure out the check engine light since it seemed to be pointing to one of the new O2 sensors. They gave us the car back with a “freeze frame” on it to try and get more data about the O2 sensor. Then we brought it back and they had it for a couple days. They replaced one of the new O2 sensors, took apart the new cataylic converter, replaced “a gasket” and gave us the care back.

The check engine light is off but the strong exhaust smell is still there, although not so much a burning smell anymore. And it’s not a sulfur smell which I’ve read about in other people’s bad converter stories.

They’ve been gracious through this and didn’t charge us anything after installing the converter, but I am no longer confident that this smell will just “go away in time.” Isn’t two weeks enough time? I’ve been out of the car for an hour now and I can still feel/taste the smell in my mouth. I’m not a smoker but it reminds me of the way my mouth felt the few times I’ve had a cigar.

I’m hoping for advice as to what’s going on with the car, but maybe more importantly how to talk to my mechanic to get this fixed once and for all.


I’m going to guess that there was an exhaust leak after the initial installation, which triggered the “Check Engine” light and caused the smell. Give it some more time but definitely bring it back if the smell persists or the “Check Engine” light comes back on.


Did the shop use genuine Toyota or aftermarket parts?

But let’s go to the beginning . . . why did the shop replace the cats and sensors in the first place?
Please go through your records and tell us what fault codes you had BEFORE all the parts were replaced

I’m also inclined to believe you may still have an exhaust leak. If the shop uses an evap/smoke machine, it will quickly find any exhaust leaks for them.

BTW . . . there are numerous Toyota technical service bulletins relating to oxygen sensors and cats.
Some of the bulletins clearly state that the engine control module software also needs to be updated to prevent a reoccurrence of the fault codes which prompted replacement of the parts in the first place.

Good comments above. Besides that, it is possible the odor is relating to the installation compounds they use to prevent leaks on the fittings. The material may take some time to set, meanwhile might smell a tad, esp when heated. Sort of like how paint dries. It smells at first, then doesn’t. The CEL could be – or not – causes by an improper installation of the cat. Hard to say. YOu might cold get another opinion I guess.


Check this out

If the shop did not update the pcm software, I strongly urge you to get it done. The bulletins I provided also make this point

The code combined with the smell tells me you still have an exhaust leak. Any shop with a hydrocarbon sniffer should be able to find it. Chances are good that there’s also a carbon trail visible with a good work light.

In your case the converter is integrated into the exhaust manifold, the front includes the exhaust manifold and bolts directly to the head, and the rear uses a “flex fitting” to attach to the header pipe. Those “flex fittings” are spring loaded connections with a soft metal “gasket” designed to seat with movement. If not properly installed, those fittings (which I hate) are a potential leak source. Since the “downstream” oxygen sensor is located after the flex fitting, a leak will also trigger a code for which the uninitiated might blame the O2 sensor.

My guess is that a good look-see at the flex joint with the car on a rack will show a carbon trail at the flex fitting. Whether I’m right or wrong, simply spending time with the car and driving it, as the tech apparently did, won’t likely fix the problem.