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VS spitting soot

maldotcom2

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I've noticed recently the whole back end of my car is covered in little specs of black soot, there's a lot of it around the exhaust and it dissipates the further away it gets. I can also wipe the tip clean, go for a drive and afterwards it will have splashes of black on it. Maybe i'm just imagining it but fuel consumption also seems higher.

The oxygen sensors were replaced not long ago and engine oil is regularly changed. Although last i checked it had consumed a bit of oil. it drives fine aside from a tick that sounds like a noisy lifter or bent pushrod.

Any ideas?
 

hako

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hako

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I'd watch the exhaust on cold starts - see if it puffs out black smoke indicating an initial rich fuel setting....if it does then maybe your coolant temp sensor is not sending the correct information to the ECU and the ECU is allowing the injectors to give an over-rich mixture.
Most Commodores have a few black 'splashes' at the rear on cold mornings especially when there has been a heavy dew - this increases the amount of condensation inside the exhaust system overnight and when the engine starts all the condensed water spit out the tailpipe...always with a bit of 'soot'. So maybe it's nothing to worry about.
Good Luck.
 

-=ApheX=-

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It may be an issue with your exhaust, with in the cat converter is heaps of platinum mesh etc, I have been told that once these cat converters have reached the end of there life they basically cannot continue to stop the carbon being extracted from the exhaust...
maybe take it to an exhuast specialist, or even ring one and ask a couple of questions and see if they can provide some insight...
Other than that, failing it's not the exhaust one can only assume it's using more oil and fuel than it should?
 

maldotcom2

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Hako, about 1 in 20 cold starts it will blow a puff of dark smoke. But it looks more like oil smoke rather than rich mixture.

Good point Aphex, might be worth using this to justify a high-flow cat. It's still running the original.
 

-=ApheX=-

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I have never heard of condensation building up in the exhaust? I have always been told that the water in the exhaust is the result of the carbon exhaust being converted in the cat to that of a watery compound... but then again i am no specialst...
 

Marcho

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Just a point to add. If is black smoke on start up then you best bet is its fuel. I had the same problem on cold mornings with my old VP.
If it's blue smoke than its oil. The second being oil getting past the rings and into you exhaust, this could lead to you need a rebuild mate so keep an eye on you oil. This can also cause the tappets to rattle or make noise.
 

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I have never heard of condensation building up in the exhaust? I have always been told that the water in the exhaust is the result of the carbon exhaust being converted in the cat to that of a watery compound... but then again i am no specialst...

Water is a by-product of the combustion of petrol which does contain hydrogen, and when petrol is burned, some of that hydrogen combines with the oxygen being used to burn it, producing water. One litre of petrol apparently produces almost 1 litre of water.

Most times the exhaust is hot enough that the water remains in the form of invisible water vapor. When the engine is cold, the exhaust pipe is cold, or the outside air is cold, this water may condense and become visible as "steam" or as liquid water dripping from the tailpipe. The insides of the exhaust will always contain carbon 'soot' which the water then picks up and comes out the exhaust black.

Some mufflers have a small hole drilled at the bottom-most point to drain this water out.
 
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