If your vehicle’s PCV valve isn’t working, you can clean it yourself by immersing it in carburetor cleaner or solvent your auto supply store deems suitable. There should be no gummy deposits or discoloration on a clear.
If your PCV valve must be replaced, buy a new one, remove the old valve, and insert the new one in its place (refer to the previous section for instructions on replacement).
Troubleshooting Catalytic Converters
your vehicle. (7 tells you what this part looks like and how it works.) It’s usually good for the life of a vehicle, but occasionally it does fail. The best thing you can do is be alert for signs of trouble and head for a service facility if you suspect that the catalytic converter is malfunctioning.
Technicians will put your vehicle on an electronic diagnostic machine to locate the source of the problem, possibly remove the oxygen sensor from the exhaust manifold or exhaust pipe ahead of the catalytic converter to see if that changes things, and replace the catalytic converter, if necessary.
The most common cause of failure in a catalytic converter in an older car is that it becomes so clogged that the exhaust gases can’t get through it to the muffler and out of the car. (If air can’t get out the rear of the vehicle, it can’t come in the front end, so the engine dies because no air is coming in to form the fuel/air mixture.
Every car sold in the U.S. since 1996 has had an OBD (On-Board Diagnostic) II system that tests the catalytic converter (among many other things). If the unit allows too much pollution to escape from the tailpipe, it illuminates the MIL and produces a trouble code that can be read by a technician with what’s called a “scan tool.”
The catalytic converter is sensitive to changes in the contents and temperature of the exhaust gases, so another possible cause for failure is if the cylinder head gasket is damaged, allowing oil or coolant to get into the combustion chamber and be burned in the cylinders.
Also, if your ignition system isn’t operating properly, unburned fuel in the exhaust gases can cause the catalytic converter to wear out or break down. This is another good reason for going for tune-ups at specified intervals! It’s against the law in many states to remove a catalytic converter and run a vehicle without one. Because the catalytic converter can become extremely hot, it’s important not to park your vehicle over a bed of dry grass or dry leaves, which could catch fire and destroy not only your vehicle but also the surrounding area!
Checking the Compression in the Cylinders
If your vehicle has been running roughly or seems to be losing power, it’s possible that there’s a lack of pressure in one or more of the cylinders. Without enough pressure, the fuel/air mixture doesn’t ignite efficiently. If one or more cylinders has a good deal less pressure than the others, the engine doesn’t run evenly.
So why wouldn’t there be enough pressure? Because something is letting the pressure escape. Where can it go? Basically, three places: either out through one of the valve openings (because the valve is improperly adjusted or so worn that it doesn’t close properly) or down past the rings on the piston or through a blown head gasket.
These rings prevent the pressure at the top of a cylinder from escaping and the oil that lubricates the engine from entering a cylinder. When the rings get worn, oil gets in and pressure gets out.