Understanding and treating engine deposits

Curing your car’s cholesterol problem

Henry P. Olsen - August 19, 2011 09:00 AM


1 The valve on the right has carbon deposits that will hurt engine performance.


2 The deposits on the fuel injector’s tips will cause fuel flow problems.


3 A cutaway view of a fuel injector with its filter in the top.


4 These very dirty tiny filters were removed from a set of port fuel injectors.


5 These fuel injectors are being cleaned in an ultrasonic bath.


6 This is what the fuel spray pattern looks like from a clean set of port fuel injectors.


7 The flow volume of fuel from a set of fuel injectors must all be within three percent of each other for proper engine performance.


8 There are a lot of different brands of in-tank fuel system cleaners.


9 The use of a through-the-rail fuel injector cleaner allows a stronger dose of cleaning chemicals than could be safely run through the fuel tank. This tool is used with a through-the-rail fuel injector cleaner solution.


10 An engine decarbonizer is used when the carbon build-up on the valves, pistons and in the combustion chambers is very heavy.


11 An engine flush chemical can clean the oil sludge deposits and free up the sticky piston rings of a high mileage engine (acting almost like an automotive fountain of youth), restoring lost engine power.


12 Chevron’s Techron Concentrate Plus is one of the best in-tank fuel system cleaners on the market. (Note: this is my opinion and that of many of the Ford, Chrysler and General Motors field service engineers that I have talked to.)

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Whenever the engine in your car is running, the gasoline IT is burning to make power is leaving behind harmful, power-robbing deposits inside your engine. Deposit formation is a normal by-product of the gasoline burning process, but if these fuel-related deposits are not properly controlled, they will cause a gradual loss of engine power, fuel economy and driveability.

The power loss and driveability symptoms that these deposits cause often occur so gradually that the driver may not even notice it, but once the deposits are cleaned from your engine, it should perform like it did when it was new.

The gasoline you buy at your local gas station is blended to conform to a minimum detergent additive standard that the federal government has established. Many gasoline retailers use a lower quality additive package that will allow power robbing deposits to build up on your engine’s intake valves, in the combustion chamber, and if your engine is fuel injected, deposits are also forming in the fuel injectors. Carbon deposits can also build up on the piston rings, causing them to stick in the piston grooves, which can lead to a loss in engine compression and cause the engine to burn oil.

The deposits that build up on the intake valves and in the ports can cause a loss in engine power because these deposits will restrict the flow of the air/fuel mixture as it flows into the engine’s cylinders. The deposits that build up in the combustion chamber can cause an engine to knock or ping because these deposits can create a hot spot in the combustion chamber thus increasing the engine’s need for higher-octane gasoline.

Fuel related deposits will also build up on, and in, the engine’s fuel injectors, which can cause a severe loss of engine performance and driveability if they are not controlled. The build-up of these various fuel related deposits will also cause an increase in the engine’s exhaust emissions, which may cause the vehicle to not pass the smog test that is required in most areas of the country.


Deposits and Performance

Back in the days of carburetor-equipped engines and leaded gasoline, a proper engine tune-up included the use of a top engine cleaner to remove the carbon deposits that built up on the intake valves and in the combustion chambers of the engine. Today’s modern fuel-injected engines may go a lot longer between scheduled tune-ups than a vintage carburetor-equipped engine, but engine decarbonization should still be part of your scheduled vehicle maintenance program. That’s because the gasoline the engine uses to make power during the combustion process is still causing power-robbing deposits to build up in your engine.

The air flow from the PCV (positive crankcase ventilation) system and EGR (exhaust gas recirculation) valves will also cause fuel- and carbon-related deposits to build up on the intake valves, which will restrict the airflow into the engine’s cylinders and cause the engine performance to diminish. The combustion process will also cause carbon deposits to build up in the combustion chamber that will negatively affect the combustion process and increase the engine’s need for higher-octane gasoline.

The carbon deposits that form on the top of the piston and in the combustion chamber will increase an engine’s need for high-octane gasoline because the deposits will artificially increase the heat in the engine’s combustion chamber. The carbon deposits that form on the intake valves both restrict the flow of the air/fuel mixture into the cylinders and negatively effect fuel vaporization. If the fuel is not fully vaporized and properly mixed with the air in the engine’s cylinders during the combustion process, part of this fuel may go out of the cylinders as unburned hydrocarbons. These unburned hydrocarbons can cause an engine to fail a smog check because the unburned hydrocarbon (HC) content in the exhaust may exceed the emission test standards. These carbon deposits can also cause cold start and driveability problems as the engine warms up because they can actually act as a sponge by momentarily absorbing some of the fuel that is need for proper combustion.


Detergent Gasoline

The gasoline that is sold at your local gas station must conform to an EPA-mandated minimum level of “detergents” to help prevent and reduce the build-up of fuel related carbon deposits that both increase exhaust emissions and reduce engine performance. Unfortunately, all the various blends and brands of gasoline are not created equal, plus some low-quality gasoline brands have additive packages that are not strong enough to keep the engine deposits under control.

Several of the world’s top automakers worked together to establish a higher “Top Tier” standard for gasoline that would contain a higher level of deposit control additives. Many gasoline retailers sell gasoline with a lower quality additive package, so unless you are always using a gasoline that conforms to “Top Tier” gasoline standards, it would be a good idea to use a fuel system cleaning chemical on a standard maintenance schedule.


Fuel Injector Deposits

The engineers at the factory programmed the computer that controls the air/fuel mixture the engine gets from its fuel injectors so each cylinder of your car’s engine would have the ideal mixture of air and vaporized gasoline at every driving condition. If the engine needs an air/fuel mixture adjustment, the computer will adjust the average air/fuel mixture either richer or leaner to match the needs of the engine.

The deposits that build up inside a fuel injector and on the fuel injector’s tip can have a severe effect on the performance of your engine. The fuel injectors are designed to spray the fuel the engine needs in a precise pattern of fine droplets that mix with the incoming air charge. If any deposits form on or near the injector tips, the deposits will degrade the spray pattern and reduce the flow of fuel from the injector.

The deposits that form on the tip of a port fuel injector occur mainly during the hot soak period after the engine is shut off; this hot soak condition causes the gasoline that is left in the fuel injectors to degrade into a hard varnish, thus initiating deposit formation. A new set of fuel injectors should flow within two to four percent of each other, but as a fuel injector gets “dirty” the spray pattern and flow from the fuel injector can cause the air/fuel mixture of each cylinder to vary by eight percent or more.

If the fuel flow and spray pattern is not the same from each fuel injector used on an engine, the air/fuel mixture delivered to each cylinder of the engine will vary. If the air/fuel mixture varies by more than six to eight percent from cylinder to cylinder, the engine will experience a loss of power, driveability and fuel mileage.

As the gasoline flows through the fuel injectors, it leaves behind deposits on the fuel injectors as well. These deposits will cause the fuel injector’s spray pattern to distort and also restrict the volume of fuel that comes from each fuel injector. A new injector will have some fuel leakage from the injector tip when it is exposed to the normally high underhood temperatures that occur after the engine is shut off. These high-heat conditions will cause the fuel on the injector tip to evaporate. As the fuel evaporates from the fuel injector tip, it will form deposits that will build up over time, negatively affecting the seating of the fuel injector pintle.

The deposits that form both on and in the fuel injector will distort the fuel injector spray pattern and restrict the fuel injector’s ability to supply the engine with the correct fuel it requires for power, good fuel economy and low exhaust emissions.


Cleaning Injectors

The use of a “Top Tier” detergent gasoline can help reduce fuel deposit formation in your fuel injectors and help clean the fuel injectors as you drive. Sometimes, more cleaning is necessary to keep the fuel injectors flowing properly. The most common fuel injection cleaning methods include in-tank fuel system cleaners, through-the-rail fuel injector cleaners, or the fuel injectors can be cleaned in an off-car ultrasonic fuel injector cleaner.

An in-tank fuel injector cleaner such as Chevron’s Techron Concentrate Plus will do a very good job of cleaning the fuel-related deposits that build up on and in an engine’s fuel injectors. The through-the-rail fuel injector cleaning method involves feeding a more concentrated cleaning solvent under pressure directly into the injector fuel rail, but even the best chemical cleaner cannot confirm the injectors are flowing properly.

The best way to clean a set of fuel injectors is with the use of an ultrasonic fuel injector cleaner because it allows the operator to measure the flow volume of the fuel injectors and observe the spray pattern of a set of fuel injectors. The fuel injectors also have fuel filters that are pressed into the inlet of each injectors; the only cleaning method that includes servicing these filters is the off-car ultrasonic cleaning method.

If you replace the fuel injectors, they should always be replaced as a set unless you are confirming the replacement injector’s flow volume and spray pattern are the same as the original injectors by flowing them on a fuel injector flow bench. Unless all the fuel injectors supply each cylinder of the engine with the correct amount of vaporized fuel, the engine will not perform as well as it should, plus the engine will emit a higher level of exhaust emissions than it should.


Cleaning the Carbon

Unless you are always using a “Top Tier” gasoline, the use of an aftermarket fuel system cleaner such as Chevron’s Techron Concentrate Plus, Lucas Fuel System Cleaner or Sea Foam to clean the carbon deposits that build up inside your engine is a good idea. The schedule for when you use a fuel system cleaner should be done on the same mileage schedule as when your engine’s oil is serviced for the best results. These fuel system cleaners can rapidly and thoroughly clean the carbon deposits on and in the fuel injectors, on the intake valves and in the combustion chambers as you drive. The chemicals in a typical fuel system cleaner “pull” carbon deposits away from metal surfaces like intake valves and fuel injectors and then burn them away in the combustion process.

A certain amount of unburned combustion by-products will make their way past the piston rings into the crankcase. These combustion by-products will cause the oil to darken in color as the oil gets contaminated or “dirty,” thus the need for regular oil changes. The sticky carbon deposits that build up on the piston rings and in the piston grooves in a high-mileage engine can cause an engine to lose compression and burn oil. The use of an engine flush product such as Gunk, Amsoil or Wynn’s can help clean the sticky deposits that build up on the piston rings of a high mileage engine and clean the sludge that can build up in the crankcase of an engine that has not been properly maintained.

A clean deposit-free engine will provide its driver with the best power, driveability and fuel economy, plus a clean engine will provide its owner with the maximum engine reliability and lower exhaust emissions.