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Old 2 Weeks Ago   #1
Join Date: Jul 2009
Location: Lakewood Ohio
Posts: 289

GTA Year: 1989
GTA Engine: 350 TPI Automatic
Opinions/Advice re: catalytic converters

My car is a 1989 5.7 with dual cats. Car has 71,000 miles. Original cats replaced about 2 years ago - had loud rattling sound and one had physical damage from a speed bump. Local muffler shop replaced them with no name economy cats. Now these things are rattling like marbles in a coffee can (the old metal kind). The shop replaced the one we thought was making the noise at no charge. Still rattling so the other one must be bad also. I've put on less than 1000 miles on the first replacement cats. The car runs very well with no issues and no SES light. I don't know what is causing the cats to fail so soon, other than their poor quality.

The car is over 25 years old and is exempt from emissions inspection. I am considering removing the cats and replacing with straight pipes. (For off-road use only!). I don't intend to sell the car, but if I did I would disclose the lack of cats to a buyer. Has anyone removed the cat(s) from these cars? Are there any engine/drivability issues that result from this? Will it set off an SES light? (No O2 sensor post cat, so I doubt it, but…).

If anyone has any experience with deleting the cat(s) on these cars I'd appreciate your input.

Last edited by 89-5.7GTA; 2 Weeks Ago at 11:11 AM.
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Old 2 Weeks Ago   #2
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Join Date: Mar 2015
Posts: 135

Re: Opinions/Advice re: catalytic converters

Originally Posted by 89-5.7GTA View Post
Are there any engine/drivability issues that result from this? Will it set off an SES light? (No O2 sensor post cat, so I doubt it, butů).
You are correct about that part. Post cat O2s are an OBD2 thing, and our cars are all OBD1. So no issues there.

Haven't done it myself yet, but have talked to several locals who have...no issues. My local shop wants to take mine out. I'll keep it in case I ever need to / want to go back to stock.
1988 Pontiac Trans Am
POCI #72200
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Old 2 Days Ago   #3
Bad luck or no luck
Join Date: Jun 2004
Location: Ravenna, OH
Posts: 1,941

GTA Year: 1987
GTA Engine: Custom
Re: Opinions/Advice re: catalytic converters

I did this to my car years ago. Even when I had to go through echeck, it wasn't an issue. I actually took the cat converter and punched it out hollow with a piece of pipe, then reinstalled it. Eventually I just replaced it with a piece of straight pipe.
87 GTA: Forged 408 LSX short block, TEA stage 2 cnc ported 243 heads, BRT Stage 3 stroker cam, LS6 intake, Longtube headers, custom 411 ECM, custom harness, custom tuned, Performabuilt stage 2 4l60E with PTC 2800 stall, 9 bolt rear with 3.70 gears and TAP girdle.

11.35 at 117 mph.
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