Cats are off, will gutting them throw the check engine light? What are my options? (1 Viewer)

Francis K

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Still waiting for my welder to finish my truck, going on two months now and another problem popped up. He had to cut the cats to get the XO fab sliders on there apparently, whether that actually needed to be done or not is a moot point as he already did it. So now that they are off the truck should I just have him gut them? They're 25 years old I highly doubt they are actually doing anything anymore other than restricting airflow. Will that trip the sensor and throw the check engine light? I know many of you enjoy the warm glow of the check engine light but I would rather avoid that.

Any other options here or anything I can do besides paying $500 for some magna flow or something?
 
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CalnSam

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i made a test pipe in place of the 2nd cat, it definitely smells worse, has more drone and is louder. Not worth the savings and i will be buying another cat when funds allow

it has triggered a CEL twice in 2 years, both times after a hard acceleration while drinking California gas
 
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They're 25 years old I highly doubt they are actually doing anything anymore other than restricting airflow.
Clearly you've never been stuck in a drive-through line behind a schmuck in a Jeep Cherokee with gutted cats, like I have. It's disgusting. If you insist on doing this, please at least re-route some of your exhaust into the cabin so that you get a good whiff of what everyone else has to put up with.
 

Francis K

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It’s a 97 and no I’m not in Cali and specifically looking to avoid an obnoxious exhaust and definitely smell, didn’t consider that. You got the wrong guy for that garbage…

So just tell him to weld them back on is what you guys suggest? Nothing should be altered or done with them?
 
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I agree that this is really weird and I'd personally be angry about it as I prefer a non hacked up exhaust. If your 80 has been maintained and run on clean fuels/etc. the cats may well be ok and have life left in them. The OG cats on my 97 with 280k plus miles seem to be doing fine with no apparent issues. New ones may be better in some way(s) but don't seem necessary to me.

Since they are off I'd run a borescope in one end (if needed) and a light in the other and see how they look. If they are intact without chunks missing/etc. and don't have build up and blockage I'd run them. If they show signs of decay or build up I'd replace them. You'll want to split the two cats to be able to inspect them more easily. Get new seals (toyota) and hardware for re-attachment and you may need to cleanup the mating surfaces a bit to help with re-sealing the joint.

Depending on the deal you have going with this welder I'd expect him to cover at least some of the costs to get this sorted since it sounds like he didn't even consult you before creating this issue.
 

Francis K

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Thanks guys, yea it is odd I wish he had said something first I would have done research here and gave him some pointers as to how other guys did it. But it is what it is it’s too late for that now, apparently he plans to just put them back on. You guys don’t think that’s a good idea?
 
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You will throw a code without the front cat in place. The fact you didn't have the light on before says they should still be working. Take a look at the honeycomb and make sure it looks good. If it's melted they're on their way out. If not, slap them back in. You don't want to buy new ones right now as the price of cats has gone through the roof with the rise in Rhodium and Palladium prices.
 

Francis K

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You will throw a code without the front cat in place. The fact you didn't have the light on before says they should still be working. Take a look at the honeycomb and make sure it looks good. If it's melted they're on their way out. If not, slap them back in. You don't want to buy new ones right now as the price of cats has gone through the roof with the rise in Rhodium and Palladium prices.


Yea trust me I looked! Just talked to him he said they look fine, I guess they’re getting slapped back on there….
 
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old trick is to use a spark plug anti fouler on the 2nd O2 to lift it further out of the exhaust stream. Worked on my Honda and my Evo in the past. :p
 

cruiserdan

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The downstream O2 will sense a catalytic inefficiency if both cats are not present and functioning.
 

cruiserdan

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Yes. The front sensor is pre-cats. The rear sensor is behind the second cat.
 
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I had cut my 94 cats out with straight pipes , for the sliders, stuck and sounded real Honda ricey at high rpm’s. Put at least one cat back in
 
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I had cut my 94 cats out with straight pipes , for the sliders, stuck and sounded real Honda ricey at high rpm’s. Put at least one cat back in
Now I want to remove my cats, if only I could get this boat anchor to rev to 8k rpm. :p
 

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