LT1 Based Engine Tech 1993-1997 LT1/LT4 Engine Related

Erratic metallic sound when accelerating

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Old Oct 8, 2005 | 10:47 AM
  #31  
MyShibbyZ28's Avatar
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Re: Erratic metallic sound when accelerating

Originally Posted by MachinistOne
I have the exact same issue that you guys are describing, off-idle at 1100-1400rpms, a metallic rattle.....it is not detonation, spark knock or what-ever, i have narrowed it down to the cat, the filler inside it is breaking down and at low rpms it creates a resonance that vibrates the loose honeycomb in the housing...

Now if any of you have brand new cats on your car you may have detonation, but at that rpm with little or no load the motor should not detonate even with 87 octane.

How many of you with this issue have original cats?
I agree with what EvilBox said. I have original cats at 181,000 miles but I don't think they are loud enough or can make the same noise I'm hearing.

As for the scanner, is it scan data or scantool or what? if it's scantool i can help you but otherwise i don't know anything about the others.
Old Oct 8, 2005 | 11:11 AM
  #32  
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From: Houston, TX
Re: Erratic metallic sound when accelerating

Originally Posted by MyShibbyZ28
I agree with what EvilBox said. I have original cats at 181,000 miles but I don't think they are loud enough or can make the same noise I'm hearing.

As for the scanner, is it scan data or scantool or what? if it's scantool i can help you but otherwise i don't know anything about the others.
It's OBD-II software I have installed on my laptop, basically the same as Autotap. I was just wondering what sensors I should look at to help me diagnose this problem as well as my 7* of knock retard.
Old Oct 8, 2005 | 11:21 AM
  #33  
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Re: Erratic metallic sound when accelerating

mine has the same problem, however it is constant with the rpms and sounds like it is only coming from one cylinder. The highest octane gas we can get here is 90. I think it is just a loose rocker arm, though I have comp R lifters, hi tech pushrods and comp rocker arms, so they usually dont come loose after tightening the key and the nut...

So perhaps detonation could be possible for me.
Old Oct 8, 2005 | 01:04 PM
  #34  
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From: Houston, TX
Re: Erratic metallic sound when accelerating

Originally Posted by Silvershark
mine has the same problem, however it is constant with the rpms and sounds like it is only coming from one cylinder. The highest octane gas we can get here is 90. I think it is just a loose rocker arm, though I have comp R lifters, hi tech pushrods and comp rocker arms, so they usually dont come loose after tightening the key and the nut...

So perhaps detonation could be possible for me.
Hmmm... now that you mention a loose rocker, I do notice a very loud tick coming from my passenger side valve cover. Would that cause knock retard?
Old Oct 8, 2005 | 03:14 PM
  #35  
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From: greenville, NC
Re: Erratic metallic sound when accelerating

yup, if its bad enough
Old Oct 8, 2005 | 09:49 PM
  #36  
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Re: Erratic metallic sound when accelerating

Found out what my rattle is today. It's my exhaust right by my cat. that's barely, hardly, not even really moving, and it's banging against my frame/floors. I mean it's just the slightest movement, i can't move my exhaust with my hand but when you push really hard to the drivers side it'll stop rattling. Maybe this is what's wrong with your guys. Just push on the cat. with your foot from the passenger side to the drivers. But who knows, the sound you're hearing could be totally different from mine.
Old Oct 8, 2005 | 10:09 PM
  #37  
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From: greenville, NC
Re: Erratic metallic sound when accelerating

im gonna try that, i recently scrapped my y pipe really bad on a speed bump so that could be it.
Old Oct 8, 2005 | 10:33 PM
  #38  
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Re: Erratic metallic sound when accelerating

my car hit a curb or something before i bought it. I don't know forsure though because the owner before me didn't know anything about camaros and the underside was all mangled by the fender and such along with the y pipe. So i think that's what did it for me, maybe that speed bump did it for you.
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