Our Favorite Online Repair Manual... Mitchell1

Clogged Catalytic Converter?



I own a 2003 Chevy Monte Carlo SS. It has 130,000 miles on it. It appears to lose power when trying to accelerate when the engine is warm. For example, cruising on the interstate at 70 mph for a short time, engine at normal operating temperature, when I need to accelerate to pass the transmission down shifts, rpm increase, yet speed does not. I think my catalytic converter is becoming plugged. It does not seem to effect acceleration when the engine is cold. Any suggestions?



Sounds like the catalytic converter to me too. If this happens at night, pull off the road to a safe stop and pop the hood. Look at the catalytic converter and see if it’s glowing red. You may have to look under the car, and not under the hood to see it. I had an 86 Corvette that had the same problem and the headers and pipes before the converter would glow red due to the blockage. A technician can diagnose this problem too with a pressure check of the exhaust system before the converter. It will show high pressure before the converter if it’s clogged.
A bad O2 sensor could be to blame, but you should be getting a check engine light too. Also a clogged fuel filter may be causing a lean condition at the high speeds you are talking about. I would have it changed if it has not been as well as crawling under the car to look for the red hot converter.

Good Luck,


Before you click out! While I know a lot about cars, I don't know a lot about YOUR CAR! A repair manual is essential and I have a way for you to get one FREE.

Click Here To Read More
(Link opens in a new window)

Learn more with our Autoshop101 courses.

Posted: 26th June 2006  |  Author: Kevin Schappell  |  Category: Exhaust

One Response to “Clogged Catalytic Converter?”

  1. ggreier says:

    Listen to Kevin Bernie, he is right. I have the very same car as you 2003 Monte Carlo SS Limited Edition. It has 150000 Km on it. That’s about 130000 miles. I could take off real fast when the engine was cold but not enough to spin the tires. This car could always spin the tires. But when if got hot and I tried to climb a double lane hill ( which I usually use the left lane because I am always passing all the Jap Crap that’s polluting our North American Highways) I had to use the right lane because it would down shift, rpm’s go up, car slows down. How embarassing! It turned out to be a clogged catalytic converter caused by long distance travel and cheap gas. It’s an expensive fix. I think I will use better gas for now on.

    Ontario Canada

Leave a Reply

You must be logged in to post a comment.

About This Blog

AutoEducation.com has been around since 1999 educating you on how cars work.

Solid advice, a little bit of fun, and even answers to your specific questions keep customers coming back. We want to help make owning a car as easy as possible for you and your family. Americans love their cars, and we are here to help you get the most out of that experience! The blog is an agile way we can respond to visitors and answer questions or post the news of the day.

Want to take your education to the next level?

Sometimes you have to get "hands-on" and there is no better place than a trade school. If you are looking for a new career, or simply just want to learn to do repairs on your own car, we can help.

We have a directory of all the trade schools, vo-tech schools and automotive colleges in the USA. Get the best education for your need, at night or full-time.

Click Here to Find an Automotive School...

We Recommend...

Online Auto Repair Information for the Do-it-Yourselfer