Intake Manifold Decarb Service.


“I didn’t even know my engine ate carbs.”

The benefits of modern direct fuel injection are many: cleaner emissions, more control over how much fuel enters the combustion chamber, as well as more precise control over the exact time fuel is injected into the engine. All this means greater efficiency, more power and less emissions. However, the direct injection system isn’t without its drawbacks.

Honda engine head showing soot build up on the back of the intake valve.

What causes the carbon and soot buildup in an engine?

During the normal combustion process for internal combustion engines, gasses, oil and fuel will seep past the piston rings and down into the crankcase of the engine. Known as blowby, these vapours will build up pressure in the crankcase. This occurs on all internal combustion engines to an extent, even in brand new cars.

To prevent the build up of pressure, nearly all modern engines employ a Positive Crankcase Ventilation (PCV) system.

The PCV system consists of a rocker cover breather, and a type of one-way valve that captures blowby vapours. This valve vents to the intake manifold after the throttle body where the intake manifold vacuum assists on pulling vapours from the crankcase.

Even though most PCV systems are filtered with a fine mesh screen or baffle of sorts, vapours and oil residues can end up coating the inside of the intake manifold. This begins to cause a build up on the inside of the intake manifold, as well as the back of the intake valves.

Without a PCV system, you would experience oil leaks would be experienced as positive pressure pushes oil seals out, and your car would require very frequent oil changes as the blowby and moisture build up in the oil, forming into engine sludge, turning the oil acidic and slowly damaging internal engine components and bearing surfaces.

Petrol is a solvent and acts like a cleaner to the surfaces it touches. Prior to direct injection becoming popular, fuel was injected into the intake port, just upstream of the intake valves. This fuel washing over the valves had a cleaning effect. Exhaust valves don’t require this cleaning because soot and carbon is burnt off during the normal combustion process and hot exhaust gasses flowing past them.

Oil buildup inside an engine intake caused by faulty PCV system.

What’s the solution to intake carbon buildups?

Grease Monkey Autowerx offers an intake decarb service where we can clean the excess oil/carbon buildup from your air intake. The results of a cleaned intake directly translate into better fuel efficiency as the air and fuel mixture can be mixed and burnt more completely.

Most cars will ‘feel’ a bit more powerful as the engine response will be improved. However, the thing most drivers will notice is how easily their vehicles will start. No more rough idles on cold mornings!

In some cars, installing an aftermarket ‘oil catch can’ is a great solution, especially on turbocharged or modified vehicles. This is a device that separates the oil vapours from the PCV gasses before they can enter the intake of the engine. Prices vary as the designs differ wildly but ask us if this is the right solution for you.

Contact Adrian and the team at Grease Monkey Autowerx at 28/684-700 Frankston - Dandenong Rd, Carrum Downs VIC 3201 or phone on 03 7037 6211 for a vehicle inspection and a free quote!

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