LT1-LT4 Modifications 1993-97 Gen II Small Block V8

Confirm my clogged cat?

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Old 01-23-2009, 07:24 AM
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Yes, a clogged cat will make you run like someone lodged a potato in the tailpipe.
The cats tend to get extra hot and start glowing.
When stuff breaks up, it can get lodged in the exhaust system and cause restrictions further back as well.

Sounds to me like an excuse to install a high-flow cat (legal) and shake out the muffler
while you're at it to see if anything falls out or rattles inside (do you have a muffler?)
Old 01-23-2009, 10:06 AM
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Originally Posted by James Montigny
Yes, a clogged cat will make you run like someone lodged a potato in the tailpipe.
The cats tend to get extra hot and start glowing.
When stuff breaks up, it can get lodged in the exhaust system and cause restrictions further back as well.

Sounds to me like an excuse to install a high-flow cat (legal) and shake out the muffler
while you're at it to see if anything falls out or rattles inside (do you have a muffler?)
High flow cats are not legal in CA. You have to install specific CA approved OBDII catalytic converters. They run something like $350 a piece. If you take a high-flow/universal cat to most shops, they won't install it for you.
Old 01-23-2009, 10:09 AM
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My exhaust is cut right before the passenger side cat. No muffler. Can a cat be "slightly" clogged? Because I can still drive my car around, it runs crappy though.

Btw, I have a high-flow being sent to me right now, and I'm going to do it myself.
Old 01-23-2009, 10:13 AM
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Originally Posted by 96blackta
My exhaust is cut right before the passenger side cat. No muffler. Can a cat be "slightly" clogged? Because I can still drive my car around, it runs crappy though.

Btw, I have a high-flow being sent to me right now, and I'm going to do it myself.
Restriction on a clogged cat can vary. Hope the new high-flow cures your problem. If not, PM me and my buddies and I can come and help you diagnose it some time.
Old 01-23-2009, 10:23 AM
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Alright, for sure. Btw, I just read the Cali Generalz part in your sig, lol. I was at the last meet by In-N-Out.
Old 01-23-2009, 10:26 AM
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Originally Posted by 96blackta
Alright, for sure. Btw, I just read the Cali Generalz part in your sig, lol. I was at the last meet by In-N-Out.
Oh ****, I talked to you, lol. I'll probably see you at some other meets. Post up your results on the swap.
Old 01-25-2009, 10:02 PM
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We know it's the cat for sure now... as of recent you can hear **** rattling inside.
Old 01-26-2009, 09:55 AM
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put your hand over the exhaust and see if it feels like its restricted
Old 01-26-2009, 05:28 PM
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a bad o2 would cause the car to go into closed loop and run like crap. id deff do a back pressure test before replacing the cats
Old 01-26-2009, 05:48 PM
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rear 02 reads what comes out of the CAT.

You can swap 02's frt/bk and see if the CEL throws a code for the frt 02..if so than the 02 is bad...otherwise CAT is dead.
Old 01-26-2009, 06:09 PM
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If you are going to put another convertor in the car there is a "break in" procedure that will prolong the life of the cat and spare you the grief of having to install another one in the future.

I think its called the flash point, ( don't quote me on that ) but after you install a new cat mainly the Ceramic block cats you have to run the engine to operating temperature and then the exhaust past a certain temperature. After the cat reaches that certain temperature the wrap expands and seals the substrate in the cat. If you don't take the car for a good drive after installing the cat the chances of failure is much higher.

Just a little information for ya,

Arthur
Old 01-26-2009, 07:22 PM
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Originally Posted by petechapter50
a bad o2 would cause the car to go into closed loop and run like crap. id deff do a back pressure test before replacing the cats
Just going into closed loop will not cause the car to run like crap.

Originally Posted by ******
rear 02 reads what comes out of the CAT.

You can swap 02's frt/bk and see if the CEL throws a code for the frt 02..if so than the 02 is bad...otherwise CAT is dead.
You can not swap pre-cat o2's and post-cat o2's, they are different.
Old 01-26-2009, 09:14 PM
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Originally Posted by REGALIS
If you are going to put another convertor in the car there is a "break in" procedure that will prolong the life of the cat and spare you the grief of having to install another one in the future.

I think its called the flash point, ( don't quote me on that ) but after you install a new cat mainly the Ceramic block cats you have to run the engine to operating temperature and then the exhaust past a certain temperature. After the cat reaches that certain temperature the wrap expands and seals the substrate in the cat. If you don't take the car for a good drive after installing the cat the chances of failure is much higher.

Just a little information for ya,

Arthur
So basically let the car idle and warm up then a good freeway drive?
Old 01-26-2009, 09:51 PM
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Originally Posted by 96blackta
So basically let the car idle and warm up then a good freeway drive?
That would work fine. Once the material is allowed to cool after the initial heat up, it looses its ability to expand again. So a good highway drive would be perfect right after you install it. I wouldn't worry about letting the car idle to warm the engine up, just let it warm up as you drive. The exhaust is usually hotter under load so driving is the best way to "cure" the cat.

Arthur



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