Enduro

I was told by Nissan mechanic that I have high carbon deposits and wanted to charge me $90 to have it removed. I do believe them since awhile back I did the cylinder compression test and the numbers were unusually high, 205-215 psi, an indication of carbon deposits.

The $90 charge would involve them hooking up some sort of device and blowing chemical into the engine for cleaning. This is not the removing the cylinder head(s) for decarbonized. The service guy told me I could buy the device/chemical or whatever at auto parts store but risk the danger of feeding too much of whatever chemical into the engine.

My question is has anyone use any chemical built for removal of excessive carbon buildup? If so what was your success and what's the procedure involve in doing so? Thanks!

dwapenyi

iTrader: (3)

wouldn't driving really hard on the highway for like a hour get rid of the deposits?

DW

Axra

I imagine they are going to use a chemical called Seafoam or something similar. One of it's applications is to pull a vacuum tube and use it to suck this stuff into the intake manifold. You keep doing it until it stalls the engine. After a few minutes you start the engine and it blows a large amount of smoke out your exhaust which is all the carbon deposits being burned off. It's actually pretty safe since it's a petroleum distillate. Anything else would cause compression problems and would do serious damage.

Daniel B. Martin

Carbon build-up is unusual with modern engines and fuels.

Did you compare your compression gauge with one or two others? Your gauge may be reading too high.

There are many fuel system cleaners on the market. These are fuel additives and most will do a good job cleaning the fuel injectors. Some also claim to clean the combustion chambers. One of the best-known is Chevron Techron. http://www.chevron.ca/ProductsServic...temCleaner.htm

I suggest you try Techron before paying $90.

Enduro

Thanks for the advice guys!

My main concern now is to get rid of the extra carbon deposits in the combustion chamber so hopefully the fuel additives will solve this problem. If the compression test still shows high value may be I'll compare my guage with another one as the next test.

One thing I forgot to mention about my car is that couple months ago I mistakenly manually shifted my auto from D to neutral then back to D, 2, and finally 1 on the highway and stalled the car as the car buckled to an abrupt stop. Would this some how cause extra carbon deposits in the combustion chamber and the reading of high psi?

Daniel B. Martin

No.

IndyMax77

Just a curiosity question: how do fuel additives work? If it cleans buildups off of one part, where does the build up then go? I would think that sending 'chunks' of stuff through the engine would be not such a good thing...Does the engine just burn it up? Why doesn't it do that the first time?

Again, just curious but it seems to me that some sort of law of conservation would apply here - the deposits have to go somewhere, they can't just disappear.

IndyMax77

Axra

There are a number of different cleaners out there. Some are fuel injector cleaners others are fuel system cleaners that help remove deposits from valves and other related parts. Make sure you keep an eye on your spark plugs when you use any additive in your fuel, and don't plan on having any emissions tests done right away.

Daniel B. Martin

I'm no chemist so this response is in the category of I Think, not I Know.

Some of the deposits are oily crusty "junk" which collects on the stems of intake valves. It is a combination of engine oil and fuel residue. The engine never had a chance to burn this material because it never reached the combustion chamber. If a solvent causes these deposits to loosen and crumble the pieces pass through the combustion chamber. Tiny pieces may burn completely, larger pieces may burn partially. The product of combustion goes out through the exhaust system.

Complete combustion of fuel depends on atomization of the incoming liquid fuel. If everything is "just right" each injector delivers a symmetrical spray pattern of tiny droplets which change state from liquid to vapor. This facilitates complete combustion and no deposits. If the fuel pressure is too low or the fuel injector tips are obstructed you get a messy assymetrical spray pattern with a variety of droplet sizes. This leads to incomplete combustion and formation of crusty deposits. A solvent may loosen these deposits and let them be swept downstream with the exhaust gases. If some of those pieces land on the Oxygen Sensors or become lodged in the Catalytic Converter... well that's unfortunate.

NZ Max

I have a friend who just did something like this to his 89 Nissan Bluebird 1.8. He said they actually disconnected the fuel line and hooked this machine up to it instead and actually ran the car on this stuff for 20 min then turned it off and left it for another 20. They then hooked up the fuel lines angain and started the car. He said that it blew the rawest bluest smoke that he hadever seen in his life for about a minute and then cleared up. He reports that his car now has a lot more power and a lot more throttle response. His car had 140000 km . So I guess it does actually do some good. It cost $167 NZD

JAY25

iTrader: (38)

they would charge me $120.00 to do this type of cleaning, the nissan dealership here in New Orleans. I guess thats about a alright.



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IndyMax77

Is that why some car manufacturers tell you not to use those additives? Because it might mess with your sensors and/or anything else?

IndyMax77

Daniel B. Martin

Yes, and the "anything else" is the fuel injectors.

When fuel passes through the fuel injectors it sweeps past the solenoid which causes the injector to open. The solenoid coil is many turns of fine copper wire covered with an insulating "paint". A solvent powerful enough to dissolve crusty deposits may also be powerful enough to dissolve that insulation. This harms the injector.

I would use a fuel system cleaner only to remedy a clogged injector problem. It's a bad idea to use it on a preventive basis "just in case".