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Unread 09-15-2014, 09:07 PM   #1
amj951
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Rattling during start up

Hey all,
So I am experiencing some rattling (rock in a can kind of rattling) when i start the jeep up when the engine is cold. I'm almost certain that it is one of the mini cats but I'm not 100% sure. It lasts just about the length of the time it takes till the engine heats up then it goes away. I am not experiencing any sort of power loss or mileage drop though, and from what ive read a bad cat= power loss and mileage drop. Anyways, my question is what else could it possibly be? I'm sure someone out here has experienced this. I don't just drop the cash on a whole new cat set up if it's not needed. BTW the jeep has 60,000 miles on it. thanks in advance!

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Unread 09-16-2014, 03:42 AM   #2
ky-homelite
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I have the same issue. Doesn't do it every morning, seems random. Doesn't seem to matter if it's extremely cold or hot outside either. Sounds like a single rock in a soup can or something, lasts maybe 3-4 seconds and that's it. It's hard to track down since it doesn't do it every cold startup, and by the time I get out of the Jeep it's stopped making the noise. I honestly have no idea where to even start looking. I'm not down on power, and still get the same horrible mileage haha!
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Unread 09-16-2014, 07:38 AM   #3
biffgnar
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Its not a given that a bad cat will show reduced power/mileage. The rattling you describe is stereotypical bad cat sound.
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Unread 09-16-2014, 12:33 PM   #4
amj951
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Quote:
Originally Posted by ky-homelite View Post
I have the same issue. Doesn't do it every morning, seems random. Doesn't seem to matter if it's extremely cold or hot outside either. Sounds like a single rock in a soup can or something, lasts maybe 3-4 seconds and that's it. It's hard to track down since it doesn't do it every cold startup, and by the time I get out of the Jeep it's stopped making the noise. I honestly have no idea where to even start looking. I'm not down on power, and still get the same horrible mileage haha!
mine started out the same way.. over time, of course, it has gotten increasingly louder and more frequent, although it does go away. that's why i am assuming it is one of my mini cats that has slowly started to break apart and hasn't actually become clogged or clogged my main cat, which i am sure will eventually happen. looks like ill just be buying a whole new replacement here shortly. anyone have any experience with the catco 9170? says its a direct replacement, but i have learned over time that a direct replacement, doesnt always mean a direct replacement.
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Unread 09-16-2014, 04:12 PM   #5
brokenyoujoint
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somethings loose or you got a bad cat.... Block your jeep. Put the ebrake on, put it in park or neutral and have a responsible person start it up while you lay in, on, under, around your jeep and listen for it. Noise issues arent exactly easy to diagnose unless you're in the first person position. I know it's easier to ask than to look but don't be afraid to get your back a little dirty and find it yourself. I'm guessing a Cat.
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Unread 09-16-2014, 04:15 PM   #6
dcope17
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How about a sticky rocker arm or lifter???
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Unread 09-16-2014, 04:48 PM   #7
amj951
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Quote:
Originally Posted by brokenyoujoint View Post
somethings loose or you got a bad cat.... Block your jeep. Put the ebrake on, put it in park or neutral and have a responsible person start it up while you lay in, on, under, around your jeep and listen for it. Noise issues arent exactly easy to diagnose unless you're in the first person position. I know it's easier to ask than to look but don't be afraid to get your back a little dirty and find it yourself. I'm guessing a Cat.
yea i've gone under and listened to it.. it's just difficult to pin point if it is for sure one of the mini cats since they are so close to the block, may need to get a stethoscope to help me out. I'm certain it is not coming from the main cat though. i was thinking that it could be a loose bolt or something originally but would a loose bolt stop rattling when the engine reaches operating temp?

I am pretty sure that it is not a sticky rocker arm of lifter.. ive watched a few videos on diagnosing a bad rocker arm or lifter and the sound is completely different.
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Unread 09-16-2014, 06:53 PM   #8
brokenyoujoint
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kinda sounds like a couple of nails in a tin can for a minute then when your jeep warms up it goes away?
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Unread 09-16-2014, 07:06 PM   #9
amj951
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Quote:
Originally Posted by brokenyoujoint View Post
kinda sounds like a couple of nails in a tin can for a minute then when your jeep warms up it goes away?
yea thats basically exactly what it sounds like. i was under it a bit ago trying to tap on the mini cats with a rubber hammer to see if i could here any rattling.. sounded like i did, but it was difficult to know for sure since the sound of the hammer tapping the cat was louder.
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Unread 09-16-2014, 09:08 PM   #10
brokenyoujoint
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cat
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