funny knocking sound
Instructor
Joined: Feb 2007
Posts: 236
Likes: 1
From: Lubbock TX
I just recently had a pop corn sounding noise comming from underneath and could not find the source. It would do it on cold mornings usually and after a short drive would go away. Finally the starter started to fail and would not fully disengage. I replaced the starter and the noise is not there anymore. Just another suggestion.
Thread Starter
Racer
Joined: Jan 2009
Posts: 279
Likes: 1
From: North Port Florida
I just recently had a pop corn sounding noise comming from underneath and could not find the source. It would do it on cold mornings usually and after a short drive would go away. Finally the starter started to fail and would not fully disengage. I replaced the starter and the noise is not there anymore. Just another suggestion.
Much obliged for the input. If for some reason the cat(s) aren't the cause, I'll look into it
Thread Starter
Racer
Joined: Jan 2009
Posts: 279
Likes: 1
From: North Port Florida
Racer
Joined: Jan 2006
Posts: 388
Likes: 2
From: Palm City Fl
This maybe the same problem I just had but not with my vette. I have a '92 caddy Allante and I thought the exhaust pipes brackets were loose and I tightened them up but the noise was still there. Found out that it was the cat converter. Replaced it and no more noise.
Thread Starter
Racer
Joined: Jan 2009
Posts: 279
Likes: 1
From: North Port Florida
noise confirmed...
To close on this, I took the Z to the dealership today to confirm my belief that the Cat(s) were failing. As I pulled in to the service entrance my check engine light came on and the DIC threw code P0430 which would later translate to the #2 Bank (right side) catalytic converter not operating efficiently. The cat is covered by the GM Emission warranty for 8 years/80,000 miles for those who wanted to know and will be covered! 
Anyway, prior to taking the car in I noted that there was an ash-gray colored soot built up in the exhaust tips on the right side. Just another indicator. Thanks all to who offered suggestions. It was/is very much appreciated! 
Anyway, prior to taking the car in I noted that there was an ash-gray colored soot built up in the exhaust tips on the right side. Just another indicator. Thanks all to who offered suggestions. It was/is very much appreciated!
Drifting
Joined: Apr 2007
Posts: 1,496
Likes: 1
From: LEBANON PA.
Hi KWIKSILVERZ:
I was wondering what the mileage is on your z when the right cat went out? Did the dealer recommend to be replaced in pairs meaning changing the left & the right sides at the same time? Good for you that the warranty covered that item. Stuff usually happens after the warranty expries.
robsc501
I was wondering what the mileage is on your z when the right cat went out? Did the dealer recommend to be replaced in pairs meaning changing the left & the right sides at the same time? Good for you that the warranty covered that item. Stuff usually happens after the warranty expries.
robsc501
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Thread Starter
Racer
Joined: Jan 2009
Posts: 279
Likes: 1
From: North Port Florida
It had around 17,400 on the clock when I first "heard" the noise, but it escalated rather fast from there. I put it the shop with 17640 on the clock. As for the replacement, no. The dealer would not change both...just the problematic one. I'm not always quick to bash dealerships, but in this case it may make them money down the road if the other cat were to go after the 8 year warranty expires. In my case I still have a few years of coverage since the original owner bought it in 2004.
