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The '96 Honda Accord that recently came into my possession was checked by my brother, the mechanic in the family, said that there may be some carbon built up in the engine. I was wondering if there is a good way to get rid of it. Maybe something I can put in the tank. I don't want to have to take anything apart if at all possible. I asked my brother at the time he mentioned it and we both got distracted talking about something else. So, I will turn to the "experts":p here.

My grandfather used to say you should take the car out onto the highway at a higher rate of speed to "blow out the carbon every once in a while."

I don't know if this has any real value or not...

That's the exact same thing my fiancé's dad said today. But, I'm not sure I'm comfortable doing that with trying to save gas....maybe I would be better off taking that momentary hit to my FE. (Just thinking aloud on that last part.)

Edit:I did do a Google search and came up with a few things. One was something called seafoam. Most of the others mentioned a fuel additive that is designed to clean out carbon.

Your mechanic meant the carbon build-up that occurs on the intake and exhaust valves, which causes them to not close completely, thereby not optimizing cylinder compression. Adding a good fuel system cleaner to a tank of gas ought to clean it up. Goto your local auto-parts store and specifically look for one that cleans valves. I need to do mine bi-annually, otherwise the build-up negatively effects my required smog inspection.

My brother recommended that I use something called gunk...I think. I don't remember off the top of my head. He said just to spray it into the air intake when the engine is running.

I can't help you there. The only product called "gunk" I have seen is an engine degreaser that is only used for the outside of the engine, not the inside, but he might be referring to some other producted by the same name?

The same or similar. I can't remember off the top of my head right now.

I've used SeaFoam for that and it seemed to do an ok job. I had to replace a head in my subaru (was like that before I used the SeaFoam). But, I noticed that the carbon buildup on the valves wasn't as thick as it was on the head I replaced it with.

Your mechanic meant the carbon build-up that occurs on the intake and exhaust valves, which causes them to not close completely, thereby not optimizing cylinder compression. Adding a good fuel system cleaner to a tank of gas ought to clean it up. Goto your local auto-parts store and specifically look for one that cleans valves. I need to do mine bi-annually, otherwise the build-up negatively effects my required smog inspection.

that sounds like good advice. My Mazda Tribute just went over 100,000 and the mileage has been dropping. I think I will give that a try.

Seafoam is very good for cleaning out your intake, clearing up rough idle, and getting rid of carbon deposits.

Another more difficult technique is steam cleaning by spraying a gentle mist into the intake while the engine is running, not so much to cause hydrolock. Make sure its an amount that logically looks like it could become steam before it gets to the cylinders. Make sure the car is warm before attempting this.

Disclaimer:
Do this at your own risk as I am not responsible for any damage done to your vehicle if you attempt to steam clean.

Do this at your own risk as I am not responsible for any damage done to your vehicle if you attempt to steam clean.

LOL :D :thumbs_up:

Excelent point!!

Yeah....I don't think I will be trying the steam clean thing. Too much risk since my only other car is undriveable.

I am not necessarily saying it’s in my view point a bad or dangers thing.
Just got a kick out of the disclaimer.
I am easily amused tonight. :D

I know peterson....I just was replying to that option for cleaning my engine. I did think it was funny as well.

From what I have gathered from mechanics forums and this forum, carbon buildup is not as much of a problem as it was 20-30 years ago. Engine technology and cleaner burning gasoline's have reduced the problem of carbon buildup from a regular problem to one that creeps up occasionally. My 91 Chevy S-10 had 350,000 miles on it when I totalled it. In the 9 years I owned it, I never had to clean out or blow out carbon buildup. Even at the end, it still got 24-25 mpg w/o being HM'ed and ran smoothly. I did drive it 30-45 minutes/day on the interstate so that could have contributed to the lack of carbon. I also kept it tuned up and did regular maintainance on it.

With egr (exhaust gas recirculation) carbon deposits are introduced right into your intake manifold affecting the intake valves, fuel injectors and spark plugs along with the cylinder walls. This affects compression and some engines more so than others. There's different engineering involved with different manufacturers. In some cases if not all, the carbon can get to the throttle plate and build up a lot of gunk. What you can do to find out is take of the intake tube that goes to the manifold/plenum and flip the throttle plate over if your intake is controlled by a throttle cable and rub your finger/s on the back side. I guarantee it will not come out the same color you put it in. That is unless of course you JUST cleaned it.

I've used Seafoam and it does seem to help clean out the carbon buildup in the cylinders... just recently I had some problems with carbon knock (hot glowing carbon chunks igniting off the mixture before the spark plug fires, its sounds very much like 'pinging', but its quieter, not as violent) and one tank with a can of Seafoam has cleared it up. My mechanic buddy's shop has a machine that will decarbonize an engine, not sure what it uses for a solvent. On my 98 Ranger, 1 cylinder had a cracked plug and was really built up with crud, easily seen with a borescope. After the cleaning (about 15 minutes) checking with the borescope showed bright metal :) They charge I think $75 to do that procedure, Seafoam is cheaper, but does take longer, and I don't think will make it bright metal, but certainly reduces the buildup a lot.

Seafoam and Tecron user here