Black Stuff!
Thread Starter
Drifting
Joined: May 2002
Posts: 1,546
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From: Back in Nebraska
Black Stuff!
Quick question. When I start my car and let it warm up I find an area behind each tail pipe where there are black spots all over the ground. It is not oil or fuel, seems to be exhaust soot and moisture from the exhaust. It only does it when the car is being warmed up. Is it a sign of the mixture being to rich? Or something more serious?
Team Owner
Joined: Aug 2006
Posts: 24,125
Likes: 15
From: Columbia Missouri
Originally Posted by Apocolips
Quick question. When I start my car and let it warm up I find an area behind each tail pipe where there are black spots all over the ground. It is not oil or fuel, seems to be exhaust soot and moisture from the exhaust. It only does it when the car is being warmed up. Is it a sign of the mixture being to rich? Or something more serious?
A little rich. Probably your idle mixture screws. Turn them inward, clockwise 1/4 turn each...same time, and see if that helps. If not, do it again until the idle gets rough.
Team Owner
Joined: Aug 2006
Posts: 24,125
Likes: 15
From: Columbia Missouri
Originally Posted by I'm Batman
On an 82 you might have a bad sensor that's causing the ECM to act up. My Cherokee had the soot problem, a few new engine sensors fixed it right up.
On a '70 it's not a puter though, and he would have a different issue than the guy in an '82 with a puter right?
When did they switch to the computer?
Instructor
Joined: Dec 2004
Posts: 216
Likes: 1
From: Lapeer Michigan
You need to run the vehicle long enough to let the pipe get hot, which stops the production of condensation. When the exhaust is hotter then the inside surface of your exhaust system, you produce condensation. That causes condensation everytime you start up the vehicle, in cold weather, you produce more. If you run the engine long enough, it will empty the water from the low lying areas, which is why you should not just jump into your vehicle in the winter, drive 1 mile and stop it. That will rust out your exhaust quickly. In the summer, you produce less condensation because the pipe and the exhaust stay at a closer temperature which produces less condensation.
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Team Owner
Joined: Aug 2006
Posts: 24,125
Likes: 15
From: Columbia Missouri
Originally Posted by 1BAD80
You need to run the vehicle long enough to let the pipe get hot, which stops the production of condensation. When the exhaust is hotter then the inside surface of your exhaust system, you produce condensation. That causes condensation everytime you start up the vehicle, in cold weather, you produce more. If you run the engine long enough, it will empty the water from the low lying areas, which is why you should not just jump into your vehicle in the winter, drive 1 mile and stop it. That will rust out your exhaust quickly. In the summer, you produce less condensation because the pipe and the exhaust stay at a closer temperature which produces less condensation.
Yeah, that's the water part, but the black is a give-away of a rich system. Usually you won't notice as much but with the cold weather, the extra moisture in the system is blowing the evidence out onto the driveway behind his car.
Team Owner
Joined: Aug 2006
Posts: 24,125
Likes: 15
From: Columbia Missouri
Originally Posted by paul67
Completely normal. Start-up rich condition.
...and I agree with that, I'm just saying him checking to make sure his idle mixture isn't too rich won't hurt anything. At the very least, it'll get him closer to the proper tune he'll need for driving in colder weather.
Drifting
Joined: Mar 2006
Posts: 1,526
Likes: 2
From: Oak Ridge NC
Is it a q-jet?
Has it ever been rebuilt?
Q-Jet fuel well plugs are known to leak which will cause a rich mixture at start-up and idle. As said in a previous post, this is normal q-jet behavior.
When a q-jet is rebuilt, these fuel well plugs are epoxied which eliminates the leak.
Do your plugs show a rich condition? If not, it may not be your mixture setting.
Perhaps some of the q-jet carb experts will chime in.
Has it ever been rebuilt?
Q-Jet fuel well plugs are known to leak which will cause a rich mixture at start-up and idle. As said in a previous post, this is normal q-jet behavior.
When a q-jet is rebuilt, these fuel well plugs are epoxied which eliminates the leak.
Do your plugs show a rich condition? If not, it may not be your mixture setting.
Perhaps some of the q-jet carb experts will chime in.
Team Owner
Joined: Aug 2006
Posts: 24,125
Likes: 15
From: Columbia Missouri
Originally Posted by glenkov48
Adjust the choke when cold. It may be closing more than is needed, causing extra rich/soot condition. Adjust the idle screws when the engine is hot.
Good call.
Melting Slicks
Joined: May 1999
Posts: 2,897
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From: Moon Township PA
What year? What carb?
This black soot is moisture condensing out with the added heat. It does indicate a rich condition. If you have a carb that is tunable, I would suggest using a vacuum gauge to tune the carb to the highest vacuum setting.
This black soot is moisture condensing out with the added heat. It does indicate a rich condition. If you have a carb that is tunable, I would suggest using a vacuum gauge to tune the carb to the highest vacuum setting.
Team Owner
Joined: Aug 2006
Posts: 24,125
Likes: 15
From: Columbia Missouri
And it may not be JUST a rich idle mixture. That's just a good place to start. Get that tuned correctly for the current temps, and if it still does it you may have to look into a rebuild for your carb, if in fact it has the above mentioned malfunction.
Le Mans Master
Joined: Jul 2000
Posts: 6,664
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From: columbia city in
Originally Posted by bluesilver82
my 82 is doing the same thing. I just have not had time to mess with balancing the throttle bodies. I have a feeling it will take several tries and at least a six pack.
Melting Slicks
Joined: Mar 2006
Posts: 3,342
Likes: 7
From: Connecticut
Originally Posted by terry82
my 82 does this .it is normal. balancing the throttle bodies wiil not help this .
Show me a car with a exhaust tip that is not dirty. (unless it's cleaned on a regular basis)
The condensation is most likley from not getting the exhaust up to temp as 1BAD80 stated.
My cars are tuned well and the pipes are always dirty.
Take your finger and run it around any tail pipe and it will most likley be black.
Condensation will shorten the life of the system.
Team Owner
Joined: Aug 2006
Posts: 24,125
Likes: 15
From: Columbia Missouri
I'm not talking about dirty pipes, I mean spitting black water on the garage floor. My pipes gets dirty from use, driving, & high revs. Yes, the exhaust coats the insides of the pipes with filth.
I'm saying that keeping the mixture, or at least making sure, is at a good ratio...you can stop the black drops of water from dripping out and making little black stains on your floor. It can be an indication of a rich idle mixture. Never said it WAS is problem and that it wasn't normal but it's a good place to start.
I'm saying that keeping the mixture, or at least making sure, is at a good ratio...you can stop the black drops of water from dripping out and making little black stains on your floor. It can be an indication of a rich idle mixture. Never said it WAS is problem and that it wasn't normal but it's a good place to start.