Menu

1A Auto Video Library
Our how-to videos have helped repair over 100 million vehicles.

Check Engine Light Smelly Exhaust How to Diagnose Catalytic Converters

Share on:

Check Engine Light Smelly Exhaust How to Diagnose Catalytic Converters

Created on: 2020-12-28

In this video, Andy explains common catalyst problems, and offers some tips and suggestions for what you can do to handle a problematic catalytic converter.

Installation Video
Watch video

Is your check engine light on, your engine runs rough, and you have poor acceleration? And your exhaust mills like rotten eggs? That's what we're gonna talk about in this video.

We scan tested the vehicle and we found that we have a catalytic converter inefficiency code on the bank two side. So, we don't have any other codes at this time but there's some things we want to check out. Under the hood, we want to take a look at the intake system, just make sure everything's tight, make sure nothing's loose, and check to see if you have any intake leaks. Now, we didn't have a fuel trim code so most likely we don't have any fuel trim issues. Everything up top visually looks okay, so let's go underneath the car.

So, we want to look at the exhaust system to see if there's any leaks. So make sure there's nothing right here. There might be a little bit of a leak right there but that's not a big concern. Anything from here back doesn't really matter, but if you see any leaks up here, especially in this...see if this gasket is leaking. That looks good. And nothing's popped off or anything, this all looks good.

The reason why you have a P0420 or P0430 is because of the catalytic converters, they're located right here. Exhaust gases are gonna go through there, they're gonna burn more the emissions out, and then the exhaust goes through the tailpipe and out through the muffler. If the catalytic converter is not working properly that's when you can get raw fuel out the exhaust pipe and that's what's gonna make it smell. This is one of the cats that came on this car, let's take a look at it.

So, how this is mounted in the car, this is the engine side and this is what goes out the exhaust and out to the muffler. What we have inside here actually looks like a honeycomb or almost like a filter or a screen, and the exhaust gases go in here, the unburnt fuel, it burns up the rest of the fuel report comes out the tailpipe. In this particular vehicle, there's an exhaust manifold that comes off the engine and mounts to this converter. There's also another converter that actually has the manifold attached to it. This vehicle happens to have a V6 engine, most vehicles that have V6 or V8 are gonna have two converters. If you only have a four-cylinder, you probably only have one. You're gonna have an O2 sensor that is before the converter that's actually monitoring what the engine is doing, the air-fuel ratio, what's burning and what's not, and then you're also going to have enough an O2 sensor after the converter that's monitoring what the catalytic converter is doing. Now, the reason why you get these codes is because the computer was monitoring the back O2 sensor and saw that the catalytic converter was not doing its job.

The reason why you would have a P0420 or a 430, the 420 is going to monitor this cat, the 430 is going to monitor this one. The reason why we had the code on this vehicle if you look in this converter, it's actually hollowed out, there's nothing in there. The reason why someone hollowed this out was the engine was barely running, it was hard to drive so someone hollowed this out so the engine could actually breeze. But in removing this, you cause a check engine light and you're polluting the environment. For the most part, catalytic converters don't just fail on their own, there's a reason why they fail, whether there's leaking oil getting into there and causing this to heat up, you have raw fuel coming in there or even coolant. If you're replacing your catalytic converters, it's a good idea to replace the O2 sensors and also the spark plug. If you had an engine misfire, raw fuel is going to get in here and bring up your brand new you cats. So if you see that check engine light flashing, definitely find out what's going on, why you have a misfire before you burn these up.

If your engine is running rough, you have lack of power, and you have an egg smell coming out the exhaust, most likely you have a catalytic converter problem. If you enjoyed this video, make sure to subscribe to our channel, ring that bell, turn on all notifications so you don't miss any of our videos.


How to Tell Shocks and Struts Are Worn - Guide to Test Signs and Symptoms

How to Tell Shocks and Struts Are Worn - Guide to Test Signs and Symptoms

Watch this video to learn how to diagnose your shocks and struts. The experts at 1A Auto show you the signs and symptoms of failing shocks, so you can learn how to check your own suspension.

Search Videos
Go To Top

Same Day Shipping

Need your part faster? Choose expedited shipping at checkout.

Guaranteed To Fit

Highest quality, direct fit replacement auto parts enforced to the strictest product standards.

USA Customer Support

Exceeding customers' expectations, our team of passionate auto enthusiasts are here to help.

Instructional Video Library

Thousands of how-to auto repair videos to guide you step-by-step through your repair.

Loading...