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Best carbon cleaner for the 4.0?

BlueC

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TexasTJ2004

I love my TJ
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HDRider

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May 26, 2022
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Arkansas
Here comes some 4,000 revs!

I took off this morning in first gear using my automatic transmission. Went to 4,200 RPM. Threw a misfire on cylinder #4. Reset the code and put Marvel Mystery oil in my gas.

1659035492748.png
 

Jerry Bransford

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I'm aware. I'm not saying it will kill or even hurt an engine in such a small quantity. I assume an engine consumes as much water driving in heavy rain. I'm just personally not a fan of doing it when there are petroleum based products available.



This is the scenario that keeps me from ever mentioning it, or anything like it, to someone who hasn't demonstrated mechanical knowledge to me. When people don't have a basic mechanical understanding, they're likely to just fuck things up in a hurry.

I've seen it before, as I'm sure you have. I had a guy see one of my engine bays and asked how I kept it clean. I said I wash it. A little later, I see him dump a 5 gal bucket of soapy water directly on his engine. He destroyed some control module in the process that cost him nearly $2k.
Any basic process can be screwed up. To not recommend something just because someone can screw it up is not my way of thinking.
 
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rubicube

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Joined
Jun 6, 2019
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312
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payson az
Carbon build up in the combustion chambers is a common problem when you baby an engine too much like that. It can cause reduced performance, knocking, and/or pinging under acceleration.

It's time to do the old time-honored "Italian tuneup. When and where safe, start doing hard full throttle accelerations to high rpms, 4k and higher. It could take time to get it cleaned out, and don't be surprised if you see bits of black gunk blowing out the exhaust.

And when you can, start driving it more aggressively and stop babying the engine. It runs better when it sees higher rpms to keep things clean.

I learned about this from a Corvette mechanic. He said few customers drove their Corvettes aggressively enough and would bring them to the dealer complaining it wasn't running right. He would repeatedly rev them hard until they were running well again.

The reason engines start knocking or pinging when the combustion chambers load with carbon is because the carbon reduces the size of the combustion chamber which raises the combustion chamber pressure during the combustion stroke which prematurely ignites the fuel causing knocking or pinging... aka premature detonation.

same with Harleys ,,,most ride with to low rpm's
 
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Jerry Bransford

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I took off this morning in first gear using my automatic transmission. Went to 4,200 RPM. Threw a misfire on cylinder #4. Reset the code and put Marvel Mystery oil in my gas.

View attachment 346522
Not going to help an engine revving to 4200 rpms. That's most likely caused by a vacuum leak or even the transmission being low on ATF causing the ATF pickup to suck in air which makes the transmission slip like it's in Neutral.
 

HDRider

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May 26, 2022
Messages
182
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Arkansas
Not going to help an engine revving to 4200 rpms. That's most likely caused by a vacuum leak or even the transmission being low on ATF causing the ATF pickup to suck in air which makes the transmission slip like it's in Neutral.

I am confused. You said this earlier, "It's time to do the old time-honored "Italian tuneup. When and where safe, start doing hard full throttle accelerations to high rpms, 4k and higher. It could take time to get it cleaned out, and don't be surprised if you see bits of black gunk blowing out the exhaust."

What am I misunderstanding? I thought you suggested revving it?
 

Jerry Bransford

TJ Guru Moderator
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Supporting Member
Joined
Nov 9, 2015
Messages
25,501
Location
Fleming Island Florida
I am confused. You said this earlier, "It's time to do the old time-honored "Italian tuneup. When and where safe, start doing hard full throttle accelerations to high rpms, 4k and higher. It could take time to get it cleaned out, and don't be surprised if you see bits of black gunk blowing out the exhaust."

What am I misunderstanding? I thought you suggested revving it?
I wasn't aware going to 4k rpms was done on purpose the way it was worded, I thought it just went to 4k rpms on its own.
 
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HDRider

TJ Enthusiast
Joined
May 26, 2022
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182
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Arkansas
I wasn't aware going to 4k rpms was done on purpose the way it was worded, I thought it just went to 4k rpms on its own.

Oh no. It was entirely purposeful.

It ran through the process with no hiccups or issue except that misfire code, which came on right when I hit 4,200 RPM.

My guess is the engine is plenty carboned up
 

FireJeep

TJ Enthusiast
Supporting Member
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Jan 4, 2018
Messages
707
Location
Virginia
I routinely do not shift the six speed until 3,000 rpms, occasionally I will go as high as 3500, then every once in a while take it to 4,000. But after our 3 1/2 week trip from VA to UT and back I am scratching my head as to why I am now getting a misfire on #1 and #6 more often than before. I replaced the plugs (old and new were/are XP985), it only seems to mis at idle, at anything above that it seems to run fine..... any thoughts? TIA