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Old 06-18-2014, 04:18 PM
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Focke Wulf's Avatar
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Replaced my front O2 sensor and spark plugs. All covered in carbon. Before fixing this problem when I turned my baby on, black carbon would Come out of the tail pipe staining the ground. Not that large. Maybe a foot by 5 inches. Anyway, started her up again and the carbon came out again. Is this natural right after I replaced everything and it will clear up over time or do I need something to clean it like 93 grade gas or something else? The problem by the way was the air filter was covered in mud and dirt.

97 TJ rocking a 2.5 engine. Automatic.
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Old 06-18-2014, 05:12 PM   #2
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It should eventually clear out. Water is a product of combustion so it may take a few weeks.

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Old 06-18-2014, 08:01 PM   #3
Knows a couple things...

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Do NOT run a higher octane grade gasoline, that could and likely would just make it worse. 87 octane gasoline ignites faster and far more easily than 89-93 octane fuels do which are purposely made to burn slower and be harder to ignite. True.

Do you tend to drive your Jeep exceptionally conservatively, never (or hardly ever) revving it hard to high RPMs? If so, that will cause carbon to build up inside the combustion chambers. A good way to clear that out is with the age-old "Italian tuneup" which is nothing more than driving it super-aggressively over a few days... when safe accelerating hard to high RPMs using wide-open throttle. That is what commonly happens to high-performance cars whose owners are afraid to drive them aggressively enough and is how most mechanics fix them.

There's another method to get rid of carbon that is done more often than the Italian Tuneup since it can be done in just a few minutes without driving aggressively. This may sound scary to a novice mechanic but done properly, it is highly effective and has been in use since WWII when aircraft mechanics discovered it. With the engine running, SLOWLY and CAREFULLY trickle (!!!) 12-16 ounces of water into the air intake while the engine is running. Slowly enough that it will take probably 2 minutes to empty the water container. Keep control of the water container, you don't want to accidentally dump the full container in all a once which would hydrolock the engine.

Keep the RPMs up as you do this because it will cause the engine to stall if you don't.

This causes little micro-shockwaves inside the combustion chamber breaking up the carbon deposits and blowing it out of the engine through the exhaust system.

I don't want to read any whining about this process from those it scares. It works, works fine, and will get rid of carbon deposits quickly and easily without any harm coming to the engine.

By the way, here's how it was discovered during WWII... to help heavily-laden bomber aircraft climb to high altitudes over Europe, water injection was added to the bomber engines which substantially increased their power. Once this started, mechanics soon noticed the engines were sparkling clean inside with no carbon deposits. This is still done to this day in some engines and some aircraft engines including jet engines.
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Old 06-18-2014, 09:37 PM   #4
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Nice post Jerry. Sounds cool. I just want to times 2 higher octane burns slower. I only use it for what it's called for like my bikes and I found premium without ethanol here. Good stuff. Use it for my bikes and mowers. Stabil is a good additive if you run 10 % ethanol gas and a tank lasts over a month. It starts to absorb water and oxidize faster that pure gas which is hard to find. The stabil added to fresh gas will help stop oxidation and water absorption also gumming. It won't do nothing for old gas. Once it's oxidized it's staying that way.
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Old 06-18-2014, 11:04 PM
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When I drive, I go easy on the gas, around 3,000 RPM at most. I don't 'stomp' on the gas at a red light. Just lighty push the gas. So you're saying to stay in the high RPMs, drive like a 16 year old kid in a tuned up BMW on the highway aka go fast for a bit?

High RPMs as in how high? 4000 RPM? That idea makes sense with the water. Only thing I'm worried about is getting my hand stuck in the fan blade XD
97 TJ rocking a 2.5 engine. Automatic.
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