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What are the symptoms of a bad cat? 

 

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 Post subject: What are the symptoms of a bad cat?
Posted: Mon Jul 25, 2005 12:28 pm 
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What kind of sounds resonate from a bad cat, and what happens to the
drivabilty of the car.

Remember when I said I had a small hole in the heat sheild under the cat. Last night there was a mechanical tapping/ticking kind of noise coming from the cat, it matched in sync with the chuffy sound coming from the exhaust headers, but at a different pitch and yeah, coming right from the cat area. And it's not a nice throbby exhaust sound, if it were the engine you'd be thinking tappets of something. If you know what I mean?
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Posted: Mon Jul 25, 2005 12:45 pm 
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Im not sure kit but it gives me something to look at as well, some strange noises eminating from the foreward parts of my exhaust (ive also been told that on a clear night ppl can see small chunks of glowing exhuast coming out under boost hehe)

So im guessing when a cat dies, the baffles/catalyst melt away and block up the exhaust? A blocked exhaust should be fairly easy to diagnose with a vac gauge.... does your car feel like its struggling to breathe?

 

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Posted: Mon Jul 25, 2005 1:04 pm 
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4.9 EF Futura wrote:
Im not sure kit but it gives me something to look at as well, some strange noises eminating from the foreward parts of my exhaust (ive also been told that on a clear night ppl can see small chunks of glowing exhuast coming out under boost hehe)

So im guessing when a cat dies, the baffles/catalyst melt away and block up the exhaust? A blocked exhaust should be fairly easy to diagnose with a vac gauge.... does your car feel like its struggling to breathe?


Yeah you could say that. Also as if the engines kind of, not raspy exactly, but you can feel increased, rough harmonics through the pedal, the gear shifter, the floor, not pronounced, but noticeable. The revs don't feel clear and smooth through the shifter and pedal. It's hard to explain. Also with the added breathlessness. Can come good, but not often these days.

I've had a few issues along these lines for a while, I'm suspecting the cat, and to a degree maybe the ISC might be sticky or something?
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Posted: Mon Jul 25, 2005 1:12 pm 
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Maybe oxy sensor too??? Wouldnt hurt to change cat to a high flow one.

 

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Posted: Mon Jul 25, 2005 7:47 pm 
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We had a bad cat once, Couldnt go near it without being scratched.

Whoops, wrong cat.

My departed XR6 had a blocked Cat and had no power whatsoever, in fact i even got dragged off by a VN V6 (but I whooped it round corners, poor lad was confused, thought race tracks were straight). I also had the worst fuel economy ever, and a burning smell.

Hope the last part helps

 

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Posted: Mon Jul 25, 2005 8:32 pm 
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i had the same problem with mine. My mechanic changed my exhaust and it still hasn't fixed the problem. I had real bad fuel economy and its alot better now that its change but i made the stupid mistake of not gaettin a high flow cat.

 

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Posted: Mon Jul 25, 2005 8:40 pm 
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generally they rattle.
and then if it gets bad enough, the car can loose lots of power, and sometimes refuse to rev.

 

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Posted: Mon Jul 25, 2005 8:44 pm 
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high fuel economy and a rise in engine temps , not to mention the smell !

 

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Posted: Mon Jul 25, 2005 10:55 pm 
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i got a new cat last year and it smells like rotten eggs, i hope it's not rooted already?!

 

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Posted: Tue Jul 26, 2005 4:00 am 
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PeppyXR6 wrote:
We had a bad cat once, Couldnt go near it without being scratched.

Whoops, wrong cat.

My departed XR6 had a blocked Cat and had no power whatsoever, in fact i even got dragged off by a VN V6 (but I whooped it round corners, poor lad was confused, thought race tracks were straight). I also had the worst fuel economy ever, and a burning smell.

Hope the last part helps


I hopped in the back seat with my Nephews about a month ago ( I let my sister drive as I had had few wines), and after a few minutes after she'd started it, I could smell something burning. I thought the amp under the seat might have been on the way out. Until I realized I was smelling exhaust. Then I couldn't figure out why as all the windows were up.
But it was a little different than your normal clean smelling exhaust, it did have a slight burning sulphur quality to it.

It sounds more and more like a Cat problem doesn't it?
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Posted: Tue Jul 26, 2005 10:27 am 
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When they go, is it possible they make the exhaust louder?

Mine as of a week ago is very raspy n loud, altho have poped it up to inspect for suspect holes maybe, no go.
Dunno whats going on, i started using shell fuel again n this happens, altho dont think fuel can change the sound of the zorst like this?
Sounds awesome, but its bit of a worry to WHAT has changed.. :|

 

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Posted: Tue Jul 26, 2005 12:08 pm 
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Daniel wrote:
When they go, is it possible they make the exhaust louder?

Mine as of a week ago is very raspy n loud, altho have poped it up to inspect for suspect holes maybe, no go.
Dunno whats going on, i started using shell fuel again n this happens, altho dont think fuel can change the sound of the zorst like this?
Sounds awesome, but its bit of a worry to WHAT has changed.. :|


My exhaust note changes with Shell Premium aswell.
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Posted: Tue Jul 26, 2005 1:19 pm 
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Get under and shake the cat. If you hear parts rattling in side you know its time to get it looked at. Fuel economy and rattling noises are also signs its time. Your best to just get a high flow cat if your budget permits. Sounds like yours is stuffed anyways.

 

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Posted: Mon Aug 01, 2005 4:47 pm 
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Well I just had the cat inspected off the car. And the first thing he said it was running rich. I'm not sure why that would be the case though.
Anyway cat is fine he said, but he did say he thought the throttle cable was sticking, he showed me by revving it up to 3500 to 4000rpm and showed me how the needle and revs just floated down really slowely. Yeah she is slow in coming down, especially how she flares at warm starts, takes a while to settle.

What do you think guys?
I don't think the cables the problem, could it be a sticky ISC doing all of that?
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 Post subject: Re: What are the symptoms of a bad cat?
Posted: Sun Dec 04, 2016 4:35 pm 
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Hi All,

I Have a 2006 Ford Falcon XR6 with a horrid rattle which sounds like it's coming from the Catalytic Converter and sometimes it's a s**t to start. See the videos in the links below.

1st Video is a cold start and this is the clip where is refused to start.
https://www.youtube.com/watch?v=1che_079v8A

The 2nd Video is of it running and rattling away.
https://www.youtube.com/watch?v=cd3574DJJQQ

Me old man is convinced the cat is shagged as he was an exhaust tech. Now no longer in the trade.

From the many hours of google searches i have done suggests the same thing also the starting problem seems to be related.

I have had the engine light come on once in the manual it states it was complaining about the Emissions system which to me is another tell tail sign that there is an issue with the Cat.

I have had all the Spark Plugs replaced as there was a misfire while at idle under load everything appeared to be okay. Also the 6 Coils had to be replaced as the old plugs were that bad they killed the Coils. I believe they were the factory 100k Plugs. The car has done 116k Km's. Since it was misfiring that would cause the Cat to become damaged and break up then clog up the exhaust system?

By NZ law: "If the vehicle was first registered prior to 1 May 2010, it is exempt from this rule and provided the exhaust system meets the objective noise level test and does not leak then it will pass a Warrant of Fitness inspection."

Which tells me that i can have a piece of Pipe or a Resonator put in. instead of a replacement Catalytic Converter. There is no O2 sensor in the cat so in theory there shouldn't be any problem in doing this.

Id like to know your Guys thoughts on the matter.
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