Do Catalytic Converters Fail?
Thread Starter
Instructor
Joined: Jul 2003
Posts: 217
Likes: 1
From: Atlanta GA
Do Catalytic Converters Fail?
I just finished rebuilding my engine on my '93 LT-1 and failed the emssions test. The test guy said that my CATs were bad.
He said, that the test involved running gas back up the tail-pipe and then running the car at 20mph; however, the car wouldn't get past 4.4mph. I did see him do this. The tech then told me that this was a clear indication that I had bad catalytic converter(s).
The CATs have 236,000 miles on them, and they passed the test last year. However, they have been sitting in the driveway or the garage for the last 90 days while I worked on the engine.
THe curious this to me is that the car does run when not on the test stand with gas blowing up its tailpipe.
I don't know enough about this so I'm throwing the question out to you guys. If I need new CATs, no problem; I just don't want to waste my time and money on a wild goose chase.
He said, that the test involved running gas back up the tail-pipe and then running the car at 20mph; however, the car wouldn't get past 4.4mph. I did see him do this. The tech then told me that this was a clear indication that I had bad catalytic converter(s).
The CATs have 236,000 miles on them, and they passed the test last year. However, they have been sitting in the driveway or the garage for the last 90 days while I worked on the engine.
THe curious this to me is that the car does run when not on the test stand with gas blowing up its tailpipe.
I don't know enough about this so I'm throwing the question out to you guys. If I need new CATs, no problem; I just don't want to waste my time and money on a wild goose chase.
Le Mans Master
Joined: Aug 2007
Posts: 8,735
Likes: 412
From: WV
I just had to replace the cat on my 89 with 129,000 miles on it ..The cat was making a rattling noise and when I removed it the inside was falling apart.So yes, cats do go bad, and with the miles you have on your car I think your lucky they lasted that long...WW
Thread Starter
Instructor
Joined: Jul 2003
Posts: 217
Likes: 1
From: Atlanta GA
Thanks. That's all I needed to know.
Team Owner
Joined: Aug 2005
Posts: 34,988
Likes: 515
From: Riverside County Southern California
Co-winner 2020 C4 of the Year - Modified
2018 Corvette of Year Finalist
2017 C4 of Year
2016 C7 of Year Finalist
St. Jude Donor '09 thru '20
I just finished rebuilding my engine on my '93 LT-1 and failed the emssions test. The test guy said that my CATs were bad.
He said, that the test involved running gas back up the tail-pipe and then running the car at 20mph; however, the car wouldn't get past 4.4mph. I did see him do this. The tech then told me that this was a clear indication that I had bad catalytic converter(s).
The CATs have 236,000 miles on them, and they passed the test last year. However, they have been sitting in the driveway or the garage for the last 90 days while I worked on the engine.
THe curious this to me is that the car does run when not on the test stand with gas blowing up its tailpipe.
I don't know enough about this so I'm throwing the question out to you guys. If I need new CATs, no problem; I just don't want to waste my time and money on a wild goose chase.
He said, that the test involved running gas back up the tail-pipe and then running the car at 20mph; however, the car wouldn't get past 4.4mph. I did see him do this. The tech then told me that this was a clear indication that I had bad catalytic converter(s).
The CATs have 236,000 miles on them, and they passed the test last year. However, they have been sitting in the driveway or the garage for the last 90 days while I worked on the engine.
THe curious this to me is that the car does run when not on the test stand with gas blowing up its tailpipe.
I don't know enough about this so I'm throwing the question out to you guys. If I need new CATs, no problem; I just don't want to waste my time and money on a wild goose chase.
Did you install a "hot" Cam? What kind? How many miles did you drive the new engine before you went to the smog shop? Was the engine cold or at operational temperature? Takes a lot to fail SMOG outside California.
Thread Starter
Instructor
Joined: Jul 2003
Posts: 217
Likes: 1
From: Atlanta GA
I hadn't put more than 10 miles on it over two days when I had it tested. Its only 2.5 miles to the emissions test from the house and it was not that hot. Engine should have been at 196 though. I had driven it earlier for about 3 miles. So I think it was hot enough.
Team Owner
Joined: Aug 2005
Posts: 34,988
Likes: 515
From: Riverside County Southern California
Co-winner 2020 C4 of the Year - Modified
2018 Corvette of Year Finalist
2017 C4 of Year
2016 C7 of Year Finalist
St. Jude Donor '09 thru '20
You did not alow the computer to learn the new cycle. Drive the Vette about 100~200 miles before to go back to SMOG.
I did the same with my LT4 and I failed. The SMOG guy told me to drive it for 200 miles, I did and I passed.
The day you go to smog, drive for a good hour, the engine should be "crispy" and that when the cats work at it's best.
I did the same with my LT4 and I failed. The SMOG guy told me to drive it for 200 miles, I did and I passed.
The day you go to smog, drive for a good hour, the engine should be "crispy" and that when the cats work at it's best.
Thread Starter
Instructor
Joined: Jul 2003
Posts: 217
Likes: 1
From: Atlanta GA
You did not alow the computer to learn the new cycle. Drive the Vette about 100~200 miles before to go back to SMOG.
I did the same with my LT4 and I failed. The SMOG guy told me to drive it for 200 miles, I did and I passed.
The day you go to smog, drive for a good hour, the engine should be "crispy" and that when the cats work at it's best.
I did the same with my LT4 and I failed. The SMOG guy told me to drive it for 200 miles, I did and I passed.
The day you go to smog, drive for a good hour, the engine should be "crispy" and that when the cats work at it's best.
Where the heck are my keys....
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
Top 10 Most Expensive Corvettes Ever Sold on Bring A Trailer
Brett Foote
10 Things Every Corvette Owner Needs (2026 Edition)
Michael S. Palmer
8 Most "Only Corvette Owners Understand" Quirks and Problems
Pouria Savadkouei
10 Reasons the C6 Z06 is Still A Performance Benchmark After 20 Years
Joe Kucinski
How Much Horsepower Every Corvette Engine "LOST" in 1972
Joe Kucinski
Top 10 DOs and DON'Ts for Protecting Your Convertible Top!
Michael S. Palmer
Top 10 Most Explosive Corvettes Ever Made: Power-to-Weight Ratio Ranked!
Joe Kucinski
150 hp to 1,250 hp: Every Corvette Generation Compared by the Specs That Matter
Joe Kucinski
8 Coolest Corvette Pace Cars (and Replicas) of All Time
Verdad Gallardo
Team Owner
Joined: Aug 2005
Posts: 34,988
Likes: 515
From: Riverside County Southern California
Co-winner 2020 C4 of the Year - Modified
2018 Corvette of Year Finalist
2017 C4 of Year
2016 C7 of Year Finalist
St. Jude Donor '09 thru '20
Thread Starter
Instructor
Joined: Jul 2003
Posts: 217
Likes: 1
From: Atlanta GA
I am curious though.
Thread Starter
Instructor
Joined: Jul 2003
Posts: 217
Likes: 1
From: Atlanta GA
Well, I ran the car 200 miles and took it back to the emissions tester good and hot.
They put the car on the tester and they had the same problem. The car wouldn't go more than 4 mph.
This time however, the technician called me over as said, "What's ASR?"
Yep. The ASR was on and the car was just trying to adjust to the slippery surface. In this case the slippery surface was the two drums that the rear wheels sit in so that they can run the car up to 20 mph for the test.
I hit the ASR button, and the car passed emissions in flying colors.
Go figure. Sure glad I didn't buy those new CATs.
This should be one for the records.
They put the car on the tester and they had the same problem. The car wouldn't go more than 4 mph.
This time however, the technician called me over as said, "What's ASR?"
Yep. The ASR was on and the car was just trying to adjust to the slippery surface. In this case the slippery surface was the two drums that the rear wheels sit in so that they can run the car up to 20 mph for the test.
I hit the ASR button, and the car passed emissions in flying colors.
Go figure. Sure glad I didn't buy those new CATs.
This should be one for the records.
Le Mans Master
Joined: Mar 2001
Posts: 7,999
Likes: 14
From: Life is just one big track event. Everything before and after is prep and warm-up and cool-down laps
Cruise-In III Veteran
Cruise-In IV Veteran
St. Jude Donor '12
I always have to remind them to turn off ASR when they put mine on the rollers.
Le Mans Master
Joined: Dec 2000
Posts: 7,839
Likes: 22
From: San Diego, Ca
Well, at least out here, the Regs recognize ASR and for those systems that can't be turned off, they're exempt from the dyno and go through a static/idle test only. No test requires some sort of gas or backpressure being shot up the tailpipe - ASR prevented the vehicle from being tested at cruise - the only thing shoved up the tailpipe is the probe - it's all outlined here: http://www.cleanairforce.com/motoris...iontesting.php
Most States have similar info somewhere.
Most States have similar info somewhere.