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Thread: Hollowed out catalytic converter bad for engine?

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    Hollowed out catalytic converter bad for engine?

    I know it's bad for the environment and all, but does it increase performance to have a hollowed out cat? Does it harm your engine? I just put a new muffler on and when I took the cat off all of the honeycomb was loose inside. I dumped it out and now it's got a hole straight through. Good or bad?
    Tom - 1984 Toyota Van, Customized Camper

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    Re: Hollowed out catalytic converter bad for engine?

    Assuming your EFI system is running correctly, most of the emissions are eliminated before they get to the cat converter. I've even heard of guys passing the emission tests without the cat. The cat is there to burn off any residual unburned fuel (pollution) that may still be there before it exits the tail pipe. If you have an o2 sensor fail or one of the other sensors, the EFI system will default into a "rich" (dirty) mode as to not damage the engine by running it too lean. In such an event the cat will significantly help reduce emissions. Using the van for an extended period with a fault like this can plug the cat and eventually render the vehicle undriveable (therefore completely eliminating emissions). Not having one or having a gutted one won't hurt the van, but will allow a bad running van to create excessive emissions for extended periods. Food for thought....... Even though I now live in an area where emission testing is not required, I personally would rather spend a few extra bucks to insure I'm doing my part in keeping the environment clean (and hope others would do the same). The aftermarket units aren't that expensive. We should all try to do our part. Tim

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    Re: Hollowed out catalytic converter bad for engine?

    Quote Originally Posted by timsrv View Post
    Assuming your EFI system is running correctly, most of the emissions are eliminated before they get to the cat converter. I've even heard of guys passing the emission tests without the cat. The cat is there to burn off any residual unburned fuel (pollution) that may still be there before it exits the tail pipe. If you have an o2 sensor fail or one of the other sensors, the EFI system will default into a "rich" (dirty) mode as to not damage the engine by running it too lean. In such an event the cat will significantly help reduce emissions. Using the van for an extended period with a fault like this can plug the cat and eventually render the vehicle undriveable (therefore completely eliminating emissions). Not having one or having a gutted one won't hurt the van, but will allow a bad running van to create excessive emissions for extended periods. Food for thought....... Even though I now live in an area where emission testing is not required, I personally would rather spend a few extra bucks to insure I'm doing my part in keeping the environment clean (and hope others would do the same). The aftermarket units aren't that expensive. We should all try to do our part. Tim
    Hey Tim, my cat has been rattling like crazy at idle as long as I've owned my van and now I seems to have stopped + the van is severely lacking power. It also occasionally stalls immediately after startup which I can only fix by stomping on the gas as I start it. I was thinking these issues were related to plugs, air filter or fuel filter all of which I plan on replacing but now that I just realized the cat rattle has stopped (my friend once described it as someone sorting recycling under the van) I'm assuming it's plugged. Out of the "daily driver" cats available on rockauto which do you recommend I go with? Walker, eastern catalytic or bosal? Bosal / walker would save me about $40 CAD over the eastern catalytic but if it's worth it I'm happy to spend the extra. Thanks so much

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    Re: Hollowed out catalytic converter bad for engine?

    Good question. I don't know which is better and/or the best value. For ease of installation I would go with a "direct fit" that already has the flanges welded to it. I got one years ago with flanges for my 89 van. The flanges were "universal" and slightly over sized. Although it bolted up (just barely) the gaskets it came with were not enough to seal. I ended up going to my local Napa and getting a variety of of similar sizes (all rated for exhaust temps), then used the closest ones along with some high temp silicone (sensor safe) to seal it up. It all worked out fine, but it's been too long for me to remember what brands and/or part numbers of things I used. Tim

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    Re: Hollowed out catalytic converter bad for engine?

    Quote Originally Posted by timsrv View Post
    Good question. I don't know which is better and/or the best value. For ease of installation I would go with a "direct fit" that already has the flanges welded to it. I got one years ago with flanges for my 89 van. The flanges were "universal" and slightly over sized. Although it bolted up (just barely) the gaskets it came with were not enough to seal. I ended up going to my local Napa and getting a variety of of similar sizes (all rated for exhaust temps), then used the closest ones along with some high temp silicone (sensor safe) to seal it up. It all worked out fine, but it's been too long for me to remember what brands and/or part numbers of things I used. Tim
    Not sure I'll be able to reuse the existing fitting anyway as the bolts are seized as hell. Maybe some time soaking in penetrating oil would sort it out. But do the symptoms I'm experiencing sound like a plugged cat to you? Or more like something else? Thanks again

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    Re: Hollowed out catalytic converter bad for engine?

    It could be. Did you check trouble codes on the ECU? Also check your EGR modulator/diaphragm to see if it's been overheated. If your EGR parts have been overheated/damaged by extreme heat, then it's a safe bet your cat is plugged up.

    If the flanges are messed-up or you don't think you can replace, just take the van to an exhaust shop and have them cut out the old and weld in a universal one. You'd be surprised as to how reasonable most exhaust shops fees are for this type of work. Tim

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    Re: Hollowed out catalytic converter bad for engine?

    I haven't checked the codes in awhile, I know my o2 sensors have been toast since I got the van a year ago though. I'll check the codes. Thanks again Tim!

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