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Black spots behind car

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Old Jan 24, 2014 | 12:52 AM
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From: If your not the lead dog the view never changes Boise, Id
Default Black spots behind car
I have a 1978 when I start it and let it warm up it leaves two black marks on the garage floor under the exhaust turn downs. It is not oil and washes right off the floor. At first I thought the engine had a lot of carbon built up but this has been going on for awhile.
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Old Jan 24, 2014 | 01:30 AM
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Originally Posted by RockyL32
I have a 1978 when I start it and let it warm up it leaves two black marks on the garage floor under the exhaust turn downs. It is not oil and washes right off the floor. At first I thought the engine had a lot of carbon built up but this has been going on for awhile.
Just a little rich with the choke on. Pretty normal especially in the winter and with a car thats not driven every day.
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Old Jan 24, 2014 | 09:03 AM
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While it's warming up, go back and look at the exhaust tips. You'll see where the black marks are coming from.
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Old Jan 24, 2014 | 09:43 AM
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It's carbon and just starting your Vette and running it for 5 minutes is probably exceeding you lifetime carbon credits you would have been allowed under Al Gore....
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Old Jan 24, 2014 | 10:04 AM
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mine did that when I got it until I removed the clogged Cat. F...Al Gore
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Old Jan 24, 2014 | 12:19 PM
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From: If your not the lead dog the view never changes Boise, Id
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Originally Posted by 81$$pit
mine did that when I got it until I removed the clogged Cat. F...Al Gore
Did your car show any other symptoms of a clogged cat? The engine in this car just doesn't seem to have the ump hit should. I know it was not a huge power maker to begin with.
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Old Jan 24, 2014 | 12:59 PM
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I have the same problem with the "black spots behind car"

Last edited by 63mako; Jan 24, 2014 at 01:03 PM.
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Old Jan 24, 2014 | 01:08 PM
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A clogged cat isn't what causes this. My car does it and it's never had cats.
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Old Jan 24, 2014 | 01:21 PM
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Originally Posted by RockyL32
Did your car show any other symptoms of a clogged cat? The engine in this car just doesn't seem to have the ump hit should. I know it was not a huge power maker to begin with.
It was running like crap and was a bit muffled. Much louder and faster now but I had the engine pulled out and gone through at the same time and had the headers gutted of all the tubes etc. No more black crap on my drywall though.

My cat got so hot at one point it almost burned down my Vette and my garage. I had a cardboard laying under it to catch all the leaks and it caught fire.
Last edited by 81$$pit; Jan 24, 2014 at 01:24 PM.
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Old Jan 24, 2014 | 01:22 PM
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Originally Posted by 63mako
I have the same problem with the "black spots behind car"

thats a GOOD problem to have...
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Old Jan 24, 2014 | 01:25 PM
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Originally Posted by 63mako
I have the same problem with the "black spots behind car"

Is that the best you can do?
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Old Jan 24, 2014 | 03:40 PM
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Need to properly set the choke and adjust A/F mixture during choke operation. Burning too rich at idle...
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Old Jan 25, 2014 | 01:28 PM
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Originally Posted by 63mako
I have the same problem with the "black spots behind car"

First thing I thought of when I read the title
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Old Jan 25, 2014 | 08:49 PM
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I just hate to tell you guys this...but,

those are black STREAKS!!!
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Old Jan 25, 2014 | 09:30 PM
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Condensation + carbon =spots
doesnt hurt to see if its a little rich
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