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Discussion Starter · #1 ·
Hey guys. I was driving and suddenly lost a lot of power. You can hear a hissing/sucking noise, maybe blowing I’m not sure coming from what sounds like the drivers side of the car. I have no idea what to do. I have to have her fixed as soon as possible though because this is my daily driver and I don’t have a backup vehicle. The only engine code it shows is a catalyst code and because of the noise it’s making I’m inclined to believe it’s something dealing with a vacuum line or something. What do I need to check first?
 

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Maybe your cat broke off inside the exhaust pipe and is rattling, and it being clogged is causing extreme backpressure leading to power loss
Keep driving it that way and you'll need an engine soon
 

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Discussion Starter · #3 ·
The code is Warm-up catalyst efficiency below threshold. Didn’t pop up until I changed one of my O2 sensors. This issue for sure sounds like air. There’s no rattling noises that I can hear. It sounds like something is sucking or blowing really hard at high RPMs
 

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The code is Warm-up catalyst efficiency below threshold. Didn’t pop up until I changed one of my O2 sensors. This issue for sure sounds like air. There’s no rattling noises that I can hear. It sounds like something is sucking or blowing really hard at high RPMs
P0421 or P0431?
 

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Discussion Starter · #7 ·
Your cat is broken
Stop driving it before you cause more damage

take the manifold off and beat them out with a crowbar at least, it’ll save your engine
It’s that bad? Oh man. I thought it was a vacuum leak and thought the issue with the cat was the 02 being faulty. I’ll take it off and clean it out
 

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You can use FLIR or an IR thermometer to check the temperature of your cats. Or, you could pop the hood at night and see if they're glowing... Often times they are. And they absolutely make a hiss when broken.

Eventually you'll either crack a piston or melt a valve driving like that if it is.
 

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It’s that bad? Oh man. I thought it was a vacuum leak and thought the issue with the cat was the 02 being faulty. I’ll take it off and clean it out
A vacuum leak or intake problem would cause codes with the front O2’s or lean/rich codes

if you have cat codes, and you do (you have either or both of P0421 or P0431) then those are triggered by the rear O2 sensors after the cats, and you have a clogged or failed cat in the manifold

if you have an OBD2 generic scan tool even, you’ll be able to read out live data of long term fuel trims, that’ll tell us if you have any issue with a type of vacuum leak, but I’m not thinking it is

I think one of your cats has broken apart and is causing the whistling noise, loss of power; and if you keep driving it, you could be in for some real serious and expensive repairs on the engine itself, as driving with the clogged cat can cause more damage (burnt exhaust valve, extreme and excessive back pressure, blown head gasket from the pressure, other damaged engine parts from the clogged exhaust/back pressure, or the possibility of the broken cat pieces getting sucked back up inside your engine and clogging something and causing serious damage)

don’t drive it till you get that header off and solved

this isn’t an EPA approved method of fixing it, but at the very least you could take the header off, and since you have the 4cyl (you do right?), you can just beat the cats out and blow compressed air through each side and have a gutted header and then put it back on, at least the car will be drivable, have power, and not risk causing severe and catastrophic engine damage then; but you’ll get both cat codes thrown then for no cats

Speaking of catastrophic engine damage, r u up to date on your timing belt?

another thing to be concerned about is the possibility of cat chunks that broke apart from the header continuing to flow down the exhaust and then just clogging up your main cat under the car too, which would have to be cut off to even be inspected for clogging, as there is no flange for it
 

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Discussion Starter · #11 ·
You can use FLIR or an IR thermometer to check the temperature of your cats. Or, you could pop the hood at night and see if they're glowing... Often times they are. And they absolutely make a hiss when broken.

Eventually you'll either crack a piston or melt a valve driving like that if it is.
They’ve never gotten hot enough to glow. So when I hollow them out what will happen afterwards? My car will still run fine right?
 

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They’ve never gotten hot enough to glow. So when I hollow them out what will happen afterwards? My car will still run fine right?
Yeah, it’ll run better than clogged that’s for sure, and no risk of damaging the engine then

you’ll just have cat codes for the missing cats, failing you for an emissions inspection if you need that because of the permanent check engine light on, unless you get a tune, spacers, or replace the header with a new one with proper cats
 

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Discussion Starter · #13 ·
Yeah, it’ll run better than clogged that’s for sure, and no risk of damaging the engine then

you’ll just have cat codes for the missing cats, failing you for an emissions inspection if you need that because of the permanent check engine light on, unless you get a tune, spacers, or replace the header with a new one with proper cats
I’ll probably get a new header eventually. We don’t have inspections in SC so the engine light being on will be my only issue with this. Will my car be any louder after this?
 

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Discussion Starter · #14 ·
I’ll probably get a new header eventually. We don’t have inspections in SC so the engine light being on will be my only issue with this. Will my car be any louder after this?
I put my hand behind the exhaust tip and it isn’t blowing out much at all. Also the manifold got hot very quickly. Like within 1 min of running it’s hot enough to burn you
 

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Then your header cats are definitely clogged
Yeah the car might be a little louder but not too much, many of us on here have done this mod for power alone, sort of a cheap header in a way; you need to do it to fix your car and prevent and further damage
 

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Discussion Starter · #16 ·
Then your header cats are definitely clogged
Yeah the car might be a little louder but not too much, many of us on here have done this mod for power alone, sort of a cheap header in a way; you need to do it to fix your car and prevent and further damage
Okay so I got it off and one side had broken completely apart. There was two big pieces of it stuck where the exhaust starts at but I think there is pieces of it clogging my exhaust up because she still doesn’t run right. She runs better, but still is missing power. Do I need to take my exhaust completely apart or would it be easier to just straight pipe her?
 

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Okay so I got it off and one side had broken completely apart. There was two big pieces of it stuck where the exhaust starts at but I think there is pieces of it clogging my exhaust up because she still doesn’t run right. She runs better, but still is missing power. Do I need to take my exhaust completely apart or would it be easier to just straight pipe her?
The pieces have probably clogged your 3rd cat under the car now, it'll have to be cut off
 

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Discussion Starter · #19 ·
[third cat has been gutted. Trying to get the rest of the crap out of the piping that’s before it. Crunk her up and revved her up to blow it out and she revved up with no issues and is very loud lol
102294
 
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