I'm sure we've all seen the commercials or read the ads at the Autoparts stores, "Free up Lost Horsepower! Increase Fuel Economy, etc.". But is there any merit to these claims? Does this service or product even do anything?? Well, I'm here to say yes, but also no.
Why do I need to Clean my valves?
First, lets talk about why carbon cleaning is needed.
Due to emissions standards, engines have been equipped with a few different systems that are directly related to carbon build up:
Exhaust Gas Recirculation (EGR): Exhaust gas is taken and routed back into the intake tract for the engine to consume. Can also be a function programmed into the variable cam timing calibration.
Positive Crankcase Ventilation (PCV): Oil vapors, and excess crank pressure, are vented from the engine valve cover into the intake track for the engine to consume.
Gasoline Direct Injection (GDI or DI): The engine's fuel injectors spray directly into the cylinder rather than into the cylinder ports (Port fuel Injection EFI or PI).
Now, the oil vapors (PCV) mixed with the heat of the engine (and possibly EGR) cause the oil to "cake" onto the intake valves and area inside of the intake port. The build up effectively reduces the intake port area, and can also reduce the ability of the intake valve to seal against the cylinder head.
At this point you may be thinking, "I have had many cars over the years, I've never needed to do this before". And you are right. Vehicles of the past have typically had fuel entering the intake port, which effectively rinsed the valves every time a fuel injector squirted fuel.
Does my engine need this service?
This is where the yes and no from earlier comes into play.
The no is pretty simple. If your vehicle is utilizing a port fuel injection system, cleaning your intake valves is something I wouldn't be too worried about.
If your car is Direct Injection, then its time we have a conversation, as the lack of fuel spray in the intake will lead to carbon clogging the ports over time.
How do I clean my intake valves?
You'll see many ways advertised to clean your intake valves. The most common is fluid ingested into a running engine through a vacuum line. This is the snake oil.
The flaws come in two areas. First, this method assumes air distribution in an intake manifold is perfectly equal between all cylinders. This is far from the truth. The fluid will most likely distribute only to the cylinders closest to where the fluid was injected. The second is in regard to the consistency of the deposits. The carbon is thick, and can be gooey. In fact, scraping it with your finger will do little to remove it. Surely, a few droplets of fluid for a few milliseconds are not going to do the job.
Clean them the right way!
The proper way to perform this service is through removal of the intake manifold and media blasting the intake valves and ports. Most commonly, the media used are walnut shells. The shells are tough enough to break the carbon free, but also light enough to not damage the cylinder and its components.
How often should I clean my valves?
We recommend this service to be performed every 30,000 miles to keep your engine in tip top shape.
If you choose to forgo this service, the consequences won't be immediately apparent. You'll loose horsepower, fuel mileage, black soot from the exhaust, and engine misfires. These issues will start gradual and worsen over time as the valves get dirtier, and the intake port area gets smaller.
How much does it cost?
Costs to perform this service can vary between different models. At minimum the procedure requires removal of the intake manifold(s), cleaning of the intake ports, new manifold gaskets, and time to reinstall the intake manifold. Procedures will vary from vehicle to vehicle.
Just for Fun
Some might have wondered about cars that come with both systems i.e. Ford mustang GT 5.0, or Subaru BRZ/Scion FRS.
Below you'll find a photo from a 2007 BMW 335i. This is a direct injection engine with a supplemental port fuel injection system added on. The port injection system only operates at wide open throttle. This particular vehicle had the valves cleaned at 25,000 miles during the installation of the port injection system. These are the valves at 70,000 miles. As you can see, the port injection has helped, but has not eliminated the need to clean the valves because they do no run full time.