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Really Bad Rattle noise

Old 10-11-2018, 07:07 PM
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MikieG1971
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Default Really Bad Rattle noise

My son was driving my 96 Lt4 6spd. He said when he shut the car off, it was fine. After school upon restarting there was a terrible rattle.
I have isolated to the "drum" looking device on the exhaust right behind the driver side exhaust manifold. Sounds like there is something loose in there.
What are your thoughts?

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Old 10-11-2018, 07:14 PM
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jmgtp
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That is a catalytic converter. There are 2 on your 94, one on each bank. Per your description, seems the catalyst has broken free and is rattling around. Solutions are replace with a new/used unit or replace with a segment of pipe and eliminate the converter (illegal).

edit: when the car is cold, rap the converter with your fist, you should hear it rattle and confirm that it is the source. Double edit - I said 94 above, but your 96 is the same. 2 converters.

Last edited by jmgtp; 10-11-2018 at 07:16 PM.
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Old 10-11-2018, 07:49 PM
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RetroGuy
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Verify first at least one of your cats is actually rattling internally and defective. If you live in a state that doesn't require catalytic converters, just replace both cats with straight pipe same as what it's connected to. I'd have a shop weld it in. If you must replace the cats, you can investigate high performance cats too.
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Old 10-12-2018, 12:00 PM
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rharker
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Even if the state doesn't have inspection requirements for having the CATS it is a federal law that governs. I would replace with OEM or equivalent Cat IMHO.
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Old 10-12-2018, 12:04 PM
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Originally Posted by rharker View Post
Even if the state doesn't have inspection requirements for having the CATS it is a federal law that governs. I would replace with OEM or equivalent Cat IMHO.
Therefore one needs to investigate prior removing...
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Old 10-12-2018, 12:08 PM
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Thereís no need to investigate, itís federal law. Plus cars without cats smell terrible. If itís a street car, I vote keep, or replace with high flow.
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Old 10-12-2018, 03:58 PM
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billschroeder5842
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Before you chuck the cats, make sure that the heat shield is not loose. I had a shild come loose on my 91 and it rattled like hell. I tighten it up with a little effort and it quieted down. Worth a look.
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Old 10-12-2018, 04:31 PM
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Mike Holmen
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Sell the old cats to a recycler and get some money towards new cats.
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Old 10-14-2018, 02:26 AM
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It's not the shield. It's inside it. Amazing how bad it sounds!
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Old 10-14-2018, 12:08 PM
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Originally Posted by MikieG1971 View Post
It's not the shield. It's inside it. Amazing how bad it sounds!
Best Bet: Start researching high flow / performance cats for your year now...

Last edited by RetroGuy; 10-14-2018 at 12:15 PM.
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Old 10-16-2018, 11:45 AM
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ctmccloskey
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I agree with the above postings that suggest you upgrade to High Flow catalytic converters.

I have a 1988 C4 and when I installed the Cat-back system that is on my car I also installed a high flow catalytic. According to my GTECH Pro I gained just over 14 hp after the Cat back system and high flow catalytic converter. They made an improvement in my power and helped keep the engine legal. I am a big believer in keeping the car's emissions clean and have everything working.

Here in Virginia they check to be sure that the catalytic is there on the Annual safety inspections. If the catalytic converters shell is missing then you will fail. But remember that this is a Federal law that prohibits the removal of the catalytic converter.

If you choose to eliminate the catalytic converters I would suggest that you remove them and clean out the ceramic insert from within and then re-install the converter shell. This way reduces the questions at inspection time.

Good Luck

Last edited by ctmccloskey; 10-17-2018 at 12:14 PM.
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Old 10-16-2018, 01:19 PM
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I would add a 3rd option if you're somewhat handy. You can hollow out the cat's if your county/state does not check emissions. Federal law requires that emissions equipment that came with the car not be removed, you hollow out the cat's no one will know. I've done this on a few vehicles over the years. My state requires annual inspection, it will not pass with bypass pipes, the cat has to be there, even though they don't check for emissions.
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Old 10-17-2018, 11:33 AM
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Originally Posted by pacoW View Post
I would add a 3rd option if you're somewhat handy. You can hollow out the cat's if your county/state does not check emissions. Federal law requires that emissions equipment that came with the car not be removed, you hollow out the cat's no one will know. I've done this on a few vehicles over the years. My state requires annual inspection, it will not pass with bypass pipes, the cat has to be there, even though they don't check for emissions.
Effective, but sneaky.
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Old 10-20-2018, 05:03 PM
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MikieG1971
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We done check anything in my state. $140 later, problem solved.
I have also noticed the "hiccup" it had under heavy and sudden acceleration is now gone as well.
WIN/WIN!!!!!
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Old 10-22-2018, 03:57 PM
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Well done getting it fixed and back on the roads!

What was the $140 for? When you share the results we all learn from your experience. This in turn will help others who experience the same issue.

I really like things when they turn into "Win-Win" situations, I wish it happened more often....
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Old 10-22-2018, 05:22 PM
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We don't check anything in my state.
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Old 10-23-2018, 04:13 PM
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Originally Posted by ctmccloskey View Post
Well done getting it fixed and back on the roads!

What was the $140 for? When you share the results we all learn from your experience. This in turn will help others who experience the same issue.

I really like things when they turn into "Win-Win" situations, I wish it happened more often....
Originally Posted by MikieG1971 View Post
We don't check anything in my state.
I don't think that answers the question...
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