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So this is a question/issue that I have had for a while now and have just been too lazy to ask. Then I ran across Johnnysks's Exhaust Dust thread over in the Canada forum and thought I might bring the question over here, hoping more folks would see and respond.

So what exactly causes this excessive carbon dust from the exhaust? One person said the cat is failing, but can this be the case if the car isn't throwing a CEL? And my car only has 33K miles on it, which is way early for a cat to go bad in my opinion.
 

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Unburned fuel....maybe this can shed light a little. Written by 3D Auto.
Carbon is a natural byproduct of the combustion process and is vented through the exhaust system. It is normal for a thin layer of carbon to cover the parts of the engine and exhaust that come into contact with the combustion process or engine exhaust. Since the introduction of unleaded fuel, carbon deposits have been greatly reduced. Normally, carbon does not present a problem.

However, through the introduction of contaminents such as oil or overly rich air/fuel ratios, carbon build-up can become excessive and reduce engine performance and require costly service or repairs.

Driving habits can also impact the amount of carbon build up. Highway driving tends to cause the engine to get sufficiently hot so as to burn away some contaminents that would otherwise become deposits. Unfortunately, short trips tend to promote the build up of carbon deposits. Having said that, in general, there are two main causes of excessive carbon buildup; burned oil and overly rich air/fuel mixtures.

Oil-based carbon build-up occurs when piston rings become worn and oil is able to leak past the rings from the crankcase. Oil can also leak from valves into the combustion chamber. Typically oil-based deposits appear as dark black and have a gummy, tar-like consistency.

Carbon tends to coat any surface that may be exposed to either the combustion process or handle engine exhaust. It is often most evident on fuel injectors, engine valves and combustion chambers. Deposits also form on the throttle body, spark plugs, intake manifold as well as in the catalytic converter and oxygen sensors. If carbon buildup is present in the EGR passages, it is probably the result of oil leaking down the valve stems. An automobile that is burning oil will tend to emit exhaust that has a bluish tint and may be a little heavier than normal.

By contrast, fuel-based carbon build-up occurs when an engine burns an excessively rich air/fuel mixture. Too much fuel will tend to produce a relatively large amount of carbon waste that is not as thick as oil deposits but it is hard, dry and tougher to remove.

Causes of fuel-based deposits often include a computer fault, a bad or leaking fuel injector or other potential reasons that cause and excessive amount of fuel to be burned during the combustion process.

In general, carbon deposits can cause a drastic drop in both fuel economy and performance. Because so many automobiles on the road rely on computers and sensors for optimal engine performance, it is easy to see how carbon deposits can play havoc with modern engines. For example, most automobiles rely on an onboard computer to adjust the air/fuel ratio in accordance to the O2 readings for optimal performance. Because oxygen sensors are exposed to engine exhaust, it is easy to see how susptible they are to contamination from carbon-deposits. Incorrect oxygen sensor readings causes the computer to make performance adjustments based on incorrect data.

Particularly thick deposits also tends to increase engine compression simply because the carbon deposits take up more space inside the combustion chamber. Abnormally high compression may result in spark knock (detonation), particularly when driving under load or accelerating. In more extreme conditions, if carbon deposits are thick enough, the top of the piston may actually come into contact with the carbon-coated cylinder head or valves. When this happens, the sound resembles a hammer noise or like a rod bearing has gone bad.

Carbon build-up can also result in excessive auto emissions. Here's how: An excessively rich fuel mixture or burned oil can create a heavy carbon residue that coats the inside of the catalytic converter. If left unchecked, excessive carbon deposits can make the catalytic converter ineffective at burning residual fuel vapors (hydrocarbons). A sufficiently compromised catalytic converter will need to be replaced. In addition, if your state requires annual auto emissions testing, you may fail simply because your catalytic converter is unable to reduce your vehicle's auto emissions.

Here are a number of signs to keep an eye out for if you suspect carbon build-up:
Engine pinging
Hesitation
Poor acceleration
Spark knock
Lack of power
Carbon coated spark plug
Repeated stalling in cold weather
Thick, bluish exhaust
Engine ping or a hammering sound

To treat carbon build-up there are off the shelf fuel addatives that tend to reduce or treat carbon build-up. In addition, there are more thorough carbon cleaning option available at most service facilities. Some of these solutions involve special chemicals, pumps and vacuum devices or blasting equipment to remove stubborn deposits.

If your engine has excessive carbon deposits, parts of the engine may need to be disassembled to do a thorough cleaning. Also, keep in mind that to do a thorough job, the intake manifold should also be removed to clean the carbon buildup from the inside of the manifold.
 

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Discussion Starter #3
+rep for the detailed description. I have been searching the net for some time to find just what you posted. If only I would have asked the forum a little earlier.

Now the question is if this is something that I should be concerned about?
 
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