Furthermore, intake and exhaust valves, in addition to spark plugs , may well be damaged and rendered useless. So, Cleaning a PCV valve may only be a short term fix. There are contaminants that will remain in the PCV valve that can never be flushed out. Also, the PCV valve has internal parts that develop wear and tear; that a simple cleaning will not fix.
Finally, proper maintenance of the Positive Crankcase Ventilation PCV system, will help reduce overall vehicle emissions. So, this part may be small and not cost much, But plays a huge role, in a healthy running engine. So, you should never have a fuel smell in your vehicle.
Consequently, if you smell fuel this could be a sign of a fuel leak. A fuel leak can be dangerous to drive with because; […]. The function of the evaporative emission control system EVAP , is to trap and store evaporative fuel emissions. The EVAP system therefore, totally eliminates fuel vapors, as a source of air pollution. But, sealing the fuel […]. A catalytic converter, is a device used; to reduce the emissions from an internal combustion engine.
So, the catalytic converter works by, breaking down unburned gases; left over by the combustion process.
One very important thing […]. Most of the images displayed are of unknown origin. We do not intend to infringe any legitimate intellectual right, artistic rights or copyright. The Positive Crankcase Ventilation PCV system; is basically a one way passage for blow-by gases to escape, in a controlled manner.
Okay -- one, two, three, go! An internal combustion engine is built around a series of hollow cylinders, in each of which is a moveable piston designed to glide up and down inside it. A mixture of air and gasoline is pumped through a system of tubes called the intake manifold through each cylinder's intake valve or valves , where a spark from a spark plug causes the mixture to explode in the open space at the top of the cylinder called the combustion chamber.
The pressure from this explosion drives the piston in the cylinder downward, where it causes the crankshaft to rotate. The rotation of the crankshaft not only pushes the piston back up into the cylinder so it can do all this again, but it also turns the gears within the car's transmission that eventually make the car move.
Meanwhile, the rising piston pushes the air and gas left over from the explosion back out of the cylinder through an exhaust valve. However -- and this is where crankcase ventilation comes in -- a certain amount of that mixture of air and gasoline is pulled down by the piston and slips through the piston rings into the crankcase, which is the protective cover that insulates the crankshaft. This escaping gas is called blow-by and it's unavoidable. It's also undesirable because the unburned gasoline in it can gunk up the system and produce problems in the crankcase.
Until the early s, these blow-by gases were removed simply by letting air circulate freely through the crankcase, wafting away the gases and venting them as emissions. Then, in the early s, positive crankshaft ventilation PCV was invented. This is now considered the beginning of automobile emission control. Positive crankcase ventilation involves recycling these gases through a valve called, appropriately, the PCV valve to the intake manifold, where they're pumped back into the cylinders for another shot at combustion.
It isn't always desirable to have these gases in the cylinders because they tend to be mostly air and can make the gas-air mixture in the cylinders a little too lean -- that is, too low on gasoline -- for effective combustion. So the blow-by gases should only be recycled when the car is traveling at slow speeds or idling.
Fortunately, when the engine is idling the air pressure in the intake manifold is lower than the air pressure in the crankcase, and it's this lower pressure which sometimes approaches pure vacuum that sucks the blow-by gases through the PCV valve and back into the intake. When the engine speeds up, the air pressure in the intake manifold increases and the suction slows down, reducing the amount of blow-by gas recycled to the cylinders. This is good, because the blow-by gases aren't needed when the engine speeds up.
In fact, when the car is up to speed, the pressure in the intake manifold can actually become higher than the pressure in the crankcase, potentially forcing the blow-by gases back into the crankcase. Since the whole point of positive crankcase ventilation is to keep these gases out of the crankcase, the PCV valve is designed to close off when this happens and block the backflow of gases.
The crankcase in a car is used as a storage place for oil, usually in a pan located below the crankshaft. While the crankshaft and the oil aren't intended to come into contact because if they did the oil would get frothed up like a thick, black milkshake , oil vapors can still find their way into the blow-by gases.
It's not a good idea for these oil vapors to be recirculated back into the cylinders along with the blow-by gases because they make the gas-air mixture too combustible, equivalent to lowering the octane of the gasoline , which in some engines can degrade performance slightly and in older engines can even cause backfire when the gas-air mixture combusts prematurely.
The oil vapors can also coat the air intake with an oily film, gradually clogging the air flow over time. If you don't drive a high performance vehicle, these problems aren't exactly crucial to your car's operation and the oil build-up can be scrubbed out periodically during maintenance, but some people and some car manufacturers prefer to have something that will scrub the oil out of the blow-by gases before they're recirculated in the first place.
Enter the oil and air separator. Small corrections cause no problems, but large corrections more than 10 to 15 points negative or positive will typically set a lean or rich DTC and turn on the MIL. Problems can also occur if someone installs the wrong PCV valve for the application. As we said earlier, the flow rate of the PCV valve is calibrated for a specific engine application.
Two valves that appear to be identical on the outside same diameter and hose fittings may have different pintle valves and springs inside, giving them very different flow rates. Watch out for cheap replacement PCV valves. Quality brand name replacement PCV valves are calibrated exactly the same as the original valves, and are designed to provide long-lasting, trouble-free performance.
Remove the valve and shake it. If it rattles, it means the pintle inside is not stuck and the valve should flow air. But there's no way to know if the spring is weak or broken, or if a buildup of varnish and deposits inside the valve is restricting flow. Check for vacuum by holding your finger over the end of the valve while the engine is idling. This test tells you if vacuum is reaching the valve, but not if the valve is flowing properly.
If you don't feel vacuum, it means the valve or hose is plugged and needs to be replaced. Use a flow tester to check the performance of the valve. This method is the best because it tests both vacuum and air flow. The volume of air that is pulled from the crankcase by the PCV system is important because it takes a certain amount of airflow to remove the blowby vapors and moisture. Tis prevents moisture contamination of the oil and the formation of sludge in the crankcase.
It can also increase oil consumption. Pinch or block off the vacuum hose to the PCV valve with the engine idling at operating temperature. The engine idle rpm should typically drop about 50 to 80 rpm before the idle speed corrects itself or you can disconnect the idle speed control motor so it won't affect idle speed during this test.
If there is no change in idle speed, check the PCV valve, hose and breather tube for a restriction or blockage. A greater change would indicate too much airflow through the PCV valve.
Check the part number on the PCV valve to see if it is the correct one for the engine. The wrong valve may flow too much air. If there is no part number, replace the valve with a new one which meets OEM specifications and test again. Measure the amount of vacuum in the crankcase.
With the engine at normal operating temperature, block off the PCV breather tube or vent to the engine usually the hose that runs from the air cleaner housing to the valve cover on the engine.
Pull out the dipstick and connect a vacuum-pressure gauge to the dipstick tube. A typical PCV system should be pulling about 1 to 3 inches of vacuum in the crankcase at idle.
If you see a significantly higher vacuum reading, the intake manifold gasket is probably leaking and pulling vacuum on the crankcase replace the leaky intake manifold gasket. If you see no vacuum, or find a buildup of pressure in the crankcase, the PCV system is plugged or is not pulling enough air through the crankcase to get rid of the blowby vapors.
NOTE: If the engine has a leaky oil pan, valve cover or intake manifold gasket leak, or leaky crankshaft seals, it will not be able to develop much vacuum in the crankcase because it is pulling in outside air which is also unfiltered and can further contaminate the oil. To find a crankcase air leak, you can lightly pressurize no more than 1 to 3 psi the crankcase with shop air via the dipstick tube or oil filler cap or breather after blocking all the other vents.
Do not use any more air pressure than this or you may create leaks where there were no leaks before. Then use a spray bottle to squirt soapy water around the gasket seams and seals.
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