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VIEW SOLUTIONS TO COMMON PROBLEMS
Engine Control Computer
Cam Position Sensor
Crankshaft Position Sensor
Select a part to view solution for common problems associated with the item.
Operation: The battery has four main functions. It supplies the energy to operate accessories when the engine is not running, it supplies energy to crank the engine, it provides additional energy when electrical demands exceed the abilities of the charging system, and it acts as a voltage stabilizer absorbing voltage fluctuations in the system. Advice: Corroded, dirty, or loose battery terminal connections can cause problems in the ignition system. If a bad battery is suspected, remove the battery from the vehicle, clean the terminal posts, top off the electrolyte levels if accessible, fully charge the battery and then load test it.
Operation: The ignition switch is an integral part of the electrical system. The majority of automotive system components do not receive any electrical current unless the ignition switch is on. Advice: It is possible for a faulty ignition switch to cause problems in the ignition system, however if a faulty ignition switch is the cause of an ignition system problem, there will probably be other ignition switch related symptoms as well.
Operation: Dielectric grease is an insulating grease. It helps to keep corrosion causing moisture out of an electrical connection. Advice: Corrosion prevention is much easier than corrosion removal. Apply a small amount of dielectric grease to the inside of the spark plug boot on the end of each coil prior to installation. Recommendations: Dielectric Grease
Operation: The spark plugs provide an air gap for the high voltage surge coming out of the coil to jump across. The resulting spark is what ignites the air fuel mixture. Advice: With the use of precious metals such as platinum, spark plugs are designed to last a lot longer than they used to. A set of double platinum plugs are supposed to last as long as 100,000 miles providing the air fuel mixture is kept properly at a 14.7 to 1 ratio. The platinum keeps the electrode from eroding, which gives the spark plug it's longevity, but a rich air fuel mixture can still foul one up quickly. Some spark plugs are tucked away in some pretty hard to get to areas. Swivel and sometimes double swivel sockets are needed to reach them. A plug boot from an old ignition wire set makes a good plug starter. A ï¿½ inch drive extension will slip nicely into the end of the old plug boot if you need a little extra reach. When removing the old plugs, lay them out in order so that if you have one or two that are burning differently than the rest you can identify which cylinders are involved. Put a small amount of anti-seize compound on the threads of the new plugs. This will help when it comes to remove them the next time. Recommendations: Swivel spark plug sockets Anti-seize compound
Operation: The ignition coil amplifies normal battery voltage that is fed into its primary windings to create high voltage pulses that are needed to fire the spark plugs. Advice: The testable parts of an ignition coil are the primary and secondary windings. The primary winding in an average coil consists of a piece of wire looped two to three hundred times around an iron core. Battery voltage passing through these hundreds of loops creates a magnetic field which emits out across the secondary windings. A magnetic field passing over a wire will induce a voltage in that wire. The secondary winding consists of a piece of very fine wire looped twenty to fifty thousand times. The more loops that are present in the winding the higher the voltage that is being induced will be. When current passing through the primary winding is shut off by the opening of the points or in the case of electronic ignition by the switching of a transistor in the ignition module, the magnetic field collapses. The high voltage that has built up in the secondary windings needs to find its way to ground. That path to ground is provided by the spark plug wire and spark plug. The spark that is created by the high voltage pulse jumping the gap at the end of the spark plug is what ignites the air fuel mixture driving the piston down. That being said, other than measuring secondary voltage output under operating conditions which requires an oscilloscope, the only tests that can be run on an ignition coil is to verify the integrity of the two windings of wire inside. Excessive resistance, or an open circuit in one of the windings are the two most common ignition coil failures. All ignition coils have a resistance specification measured in ohms, for both primary and secondary windings. If the ohms measurement for either the primary or secondary windings on the coil you are testing falls outside the parameters of the specification, it needs to be replaced. Recommendations: Volt / Ohm meter
Operation: Some ignition systems do not use a conventional ignition module. Instead the Engine Control Computer takes over the functions of the ignition module. Advice: Incorporating the ignition module into the Engine Control Computer helps in the dependability department. The ignition module is no longer subjected to the harsh environment of living under the hood. However if the ignition module portion of the Engine Control Computer does fail, the cost of replacement is much higher. Use the repair guides and Wells tester to thoroughly check all other components of the ignition system before condemning the Engine Control Computer. Recommendations: Repair guides Wells Tester
Operation: The position of the camshaft is directly related to the intake and exhaust valves opening and closing. In order for the computer to determine the optimum time to fire the spark plug it must know the exact position of the camshaft lobes. The camshaft position sensor sends a signal to the computer providing this information. Advice: Location of the camshaft position sensor varies greatly. Some are mounted on the front of the engine near the end of the camshaft. On some DIS equipped models the camshaft position sensor is located where the distributor used to be and is driven off the same worm gear on the camshaft that used to drive the distributor. Some are mounted behind the harmonic balancer For exact location check the repair guides for the vehicle that you are working on. Whenever possible test the old part before replacing it. AutoZone has the tools to test most camshaft position sensors. Check the Wells Engine Management test sheets to see if the part number for the camshaft position sensor you are trying to test is supported with a test procedure. Recommendations: Repair guides Wells Tester
Operation: The position of the crankshaft is directly related to when the piston reaches top dead center. In order for the computer to determine the optimum time to fire the spark plug it must know the exact position of the piston. The crankshaft position sensor sends a signal to the computer providing this information as well as engine speed or RPM (revolutions per minute). Advice: The crankshaft position sensor is usually found on the front or rear of the engine near the crankshaft or sometimes it is mounted in the transmission bell housing and takes it's reading off of the ring gear. Check the repair guides for the vehicle that you are working on. Whenever possible test the old part before replacing it. AutoZone has the tools to test most crankshaft position sensors. Check the Wells Engine Management test sheets to see if the part number for the crankshaft position sensor you are trying to test is supported with a test procedure. Recommendations: Repair guides Wells Tester
Operation: The knock sensor sends a voltage pulse to the computer whenever it detects the vibrations caused by metal slapping against metal, such as the conditions caused by spark knock. When the knock sensor sends a voltage pulse, the computer retards the timing in an effort to stop the spark knock. Advice: Spark knock can be caused by two things. The ignition timing could be too far advanced, firing the spark plug too soon, or there is an excessive amount of heat in the combustion chamber causing the air fuel mixture to explode before the spark plug fires. If the cause of the spark knock is excessive heat, then retarding the timing may have no effect on the spark knock. This could make it look like the knock sensor is bad since the spark knock does not go away. Whenever possible test the knock sensor before replacing it. AutoZone has the tools to test most knock sensors. Check the Wells Engine Management test sheets to see if the part number for the knock sensor you are trying to test is supported with a test procedure. Most knock sensors screw into a threaded hole on the side of the engine block. Sometimes it is hard to determine one sensor from another in a given area. Check the repair guides for wiring diagrams that will tell you the color of the wires for the sensor you are trying to find. Recommendations: Repair guides Wells Tester