C4 Tech/Performance L98 Corvette and LT1 Corvette Technical Info, Internal Engine, External Engine

Remove the cat???

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Old Nov 1, 2010 | 03:15 PM
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Default Remove the cat???

My mechanic recommends removing the cat. He says it will "Breathe better" and run better. He did a tune up on it and it runs MUCH better, but still has a stumble in the idle and when its hot, sometimes is hard to restart....it acts like its flooded or the choke is closed....even though there is no choke. He thinks removing the cat will allow it to breathe better and then he wants to adjust the CFI to loose the stumble. Is he jerking me around or is this sounding about right???
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Old Nov 1, 2010 | 03:28 PM
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For the 3+ hp and hollow sound it isn't worth it. It is nice to have a clean running car. Leave it on and spend money elsewhere (like your ignition system).
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Old Nov 1, 2010 | 04:12 PM
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Around here you have to do that kind of thing yourself no mechanic would touch it. Our state doesn't have inspections yet but they do come down hard on mechanics that do it. I'm not sure if that's a state or national law.
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Old Nov 1, 2010 | 04:20 PM
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Originally Posted by turbotim23
Around here you have to do that kind of thing yourself no mechanic would touch it. Our state doesn't have inspections yet but they do come down hard on mechanics that do it. I'm not sure if that's a state or national law.
Tampering with emissions equipment is federal stuff.
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Old Nov 2, 2010 | 07:56 PM
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what year is your vette?
If it's an L98 car it will be significantly louder without the cats. (ask me how I know)
You can just bust out the bricks and put the pipes back on for little money. I would do it only if the cats plug up.

JS
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Old Nov 2, 2010 | 09:11 PM
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You did not say your cat is cluged so if not he is jerking you around. If your car is right it will not stumble be hard to start ect. with cat on. Think you need a new mechanic.
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Old Nov 3, 2010 | 06:29 PM
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I agree with hookedo73 Find a good mechanic who can test your converters. Dont spend money on stuff you don't need or might cause you problems down the road.
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Old Nov 4, 2010 | 12:01 AM
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Originally Posted by hooked073
You did not say your cat is cluged so if not he is jerking you around. If your car is right it will not stumble be hard to start ect. with cat on. Think you need a new mechanic.


If your cats aren't broken up or melting down or otherwise clogged, they have nothing to do with your trouble.

What was included with the "tune up"? Plugs, wires, cap and rotor?
Adjusting the CFI is a good place to start. Fuel pump, fuel filter come to mind. Any oil smoke? Antifreeze smoke?

I would find another mechanic. Contact a local Corvette Club, they may lead you in the direction of someone qualified in CFI service. It sounds to me like this guy has no idea what's wrong. I would be very suspect of any mechanic that suggests removing a perfectly functioning, and required piece of equipment before trying to find the real issue. JMHO
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Old Nov 4, 2010 | 06:47 AM
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Probably the convertor is Ok the problem lies with the mechanic. Replace him and you should be OK
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Old Nov 4, 2010 | 07:23 PM
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The groups opinion is pretty much the same......leave the cat.....The mechanic never said anythnig about the cat being bad.....just that it would let the engine breathe better and THEN he wanted to fine tune the CFI stumble at idle and hard start after its hot. The cat WILL STAY. Mechanic??? Not so much. I have found a place where the ONLY cars they work on are Vettes. A bit more expensive on the labor rate, but it looks like it will be worth it for the CFI experience. Thanks to all for the input.
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Old Nov 4, 2010 | 07:40 PM
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Originally Posted by Shark Racer
Tampering with emissions equipment is federal stuff.
It can be up to a 5-figure fine for a shop to remove a working catalytic converter from a car so equipped.

If you have to go thru an emissions test to get new license tabs, then a lack of a cat is going to be a problem.

Find another shop with reputable people.
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Old Nov 6, 2010 | 03:35 AM
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You can test the converter for blockage while on the car to see if it's even the problem before you even bother. Since he's offering to remove your cat I assume Florida has no emissions testing.

This guy has been a mechanic for the last 43 years.

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Old Nov 8, 2010 | 02:06 PM
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Not sure about the stock system but can you simply disconnect part of the exhaust before the cat so you can vent to atmosphere and test it?
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