Automotive Solutions of London on Engine Maintenance.

Air Injection System

Description: First appearing on cars in 1968, air injection systems consist of a network of hoses and tubes, a belt-driven air pump and air-management valves. Since that time, air injection systems have become more diverse in nature, sometimes using the onboard computer to control system operation. Some engines use pulse-air systems that do not inject air from an air pump. Instead, alternating pressures in the exhaust stream are used to pull air into the exhaust system. Once, all engines were equipped with air injection. Today, it’s a fading technology because the universal use of fuel injection has allowed tighter control of the engine’s fuel delivery, significantly cleaning up the engine by itself.

Purpose: Essentially an emissions “add-on” installed by the automakers to help further clean up emissions, the air injection system supplies air to the exhaust stream to promote additional burning of exhaust gases such as hydrocarbons (abbreviated as HC) and carbon monoxide (abbreviated as CO). Some systems also supply air to the catalytic converter to further reduce HC, CO and oxides of nitrogen (NOx), a major contributor to photochemical “smog.”

Maintenance Tips/Suggestions: Air injection systems require little maintenance, but if your car has one it shouldn’t be completely ignored, either. Periodically, the air pump drive belt should be checked to make sure it’s in good condition and properly tensioned. Depending on the application, there may be a separate drive belt, or the pump may be driven by the same belt as other engine accessories. To determine if your car has an air injection system, refer to the Vehicle Emission Control Information (VECI) label underneath the hood, which will call out this emissions subsystem if so equipped. Symptoms of problems in the air injection system include a failed emissions test, a broken air pump belt, backfiring through the exhaust, and an overheated/restricted catalytic converter. You may want to consult with a professional technician to pinpoint the exact cause.

Crankcase Ventilation

Description: The crankcase ventilation system, often called positive crankcase ventilation (PCV), consists of a PCV valve or metered orifice (calibrated opening), its vacuum hose or line, a supply hose providing air into the crankcase, and on some applications, a breather filter to clean the air provided to the supply hose.

Purpose: The purpose of the PCV valve is to regulate the flow of crankcase fumes into the intake manifold where they can be burned. Prior to 1963, cars had no PCV and used road draft tubes that just left the hydrocarbon emissions from the crankcase out into the open air. The PCV valve also has a secondary role as a check valve, to prevent flow back into the crankcase. This prevents potential ignition of the crankcase fumes, should the engine backfire. The PCV system is also crucial for to proper engine sealing. The system alleviates crankcase pressure, which can push out on seals and gaskets, contributing to oil leaks.

Maintenance Tips/Suggestions: Often times, the PCV system gets completely overlooked during routine maintenance. This is unfortunate, because PCV faults often mimic problems in other areas. Check your owner’s manual for PCV maintenance intervals and replace the valve as recommended. Oil leaks are one clue of a faulty PCV system. Leaking valve cover gaskets and rear main seals are but a few examples. If the PCV system isn't operating correctly, crankcase pressure can build and force oil past gaskets and seals that would have otherwise been OK.

Drivability problems can also result from the PCV system. Hesitation and surging can occur if the wrong valve is used or there’s a leak in the PCV vacuum hose. You can perform a quick visual check of the PCV system, but it can be tough to see certain parts because of today’s crammed engine compartments. With the engine off, check the PCV hose by looking for soft spots, as well as for signs of cracking and swelling. Also make sure that the PCV valve is properly seated in its grommet. Inspect the breather filter and the area inside the air filter housing for oil. Oil in the breather filter may be a clue to gasket leaks in the crankcase or the presence of excessive blowby gases in the crankcase. If a basic visual check doesn’t offer any clues and you suspect a problem with the PCV system, take your car to a professional service technician.

Continuously Variable Transmission

Description: A Continuously Variable Transmission (CVT) uses an arrangement of pulleys and bands to achieve an unlimited variation between the highest and lowest ratios. Unlike conventional automotive transmissions, CVTs do not employ a graduating arrangement of fixed gear ratios to deliver power transmission. CVTs have seen spotty vehicle applications over the years, but have staged a recent comeback due to improving and emerging technologies.

Purpose: CVTs help the engine stay closer to its most efficient operating range, which can help both performance and fuel economy. CVTs may also offer manufacturers different economies of scale for transmission manufacturing.

Maintenance Tips/Suggestions: CVTs require a different maintenance regimen than conventional manual or automatic transmissions. Refer to your car’s owner’s manual for specific recommendations for CVT maintenance.

Cylinder Block

Description: The cylinder block is a casting generally made out of iron or aluminium and holds the crankshaft, connecting rods, pistons and camshaft (cam-in-block, overhead valves only). The cylinder block has numerous machined surfaces to provide a precision fit to mating parts.

Purpose: The cylinder block serves as the main structural component of the engine and houses what’s commonly referred to as "the bottom end" (crankshaft, rods, pistons). The cylinder block is extremely strong so it can withstand the rigors of engine torque and vibration, while supporting all attached engine accessories and the transmission.

Maintenance Tips/Suggestions: The engine in your car will last for many thousands of miles if driven and cared for properly. The best way to care for the cylinder block is to follow a good maintenance regimen. This includes regular oil and filter changes, engine performance check-ups, and cooling system maintenance. If you notice that engine performance drops off, that the engine is using oil, or observe problems with coolant temperature or oil pressure, it’s wise to have these looked into as soon as possible by a qualified professional.

Cylinder Head

Description: A cylinder head is a casting generally made out of iron or aluminium that holds the valves, valve springs and retainers and one or two camshafts (overhead cam engines only). The cylinder head has numerous machined surfaces to provide a precision fit to mating parts. Inline four- and six-cylinder engines have one cylinder head. V6, V8 and V10 engines have two cylinder heads.

Maintenance Tips/Suggestions: The engine in your car will last for many thousands of kilometres if driven and cared for properly. The best way to care for the cylinder head is to follow a good maintenance regimen. This includes regular oil and filter changes, engine performance check-ups, and cooling system maintenance. The main enemy of the cylinder head is overheating. If you notice that the engine temperature is higher than normal, take your car to a good repair shop as soon as possible. Overheating can quickly warp aluminium cylinder heads and contribute to head gasket failure. Any time you notice engine performance dropping off, or observe problems with coolant temperature or oil pressure, it’s wise to have these looked into as soon as possible by a qualified professional.

Engine Sensors

Description: Sensors measure a variety of operating parameters that help to reduce emissions and also serve functions for the engine, transmission and other systems. These sensors generally include the manifold air temperature sensor, coolant temperature sensor, manifold absolute pressure sensor, airflow sensor, throttle position sensor, vehicle speed sensor and oxygen sensors.

Purpose: All of these sensors provide critical operating information to the vehicle’s powertrain control module, the onboard computer that compares the signals from the sensors to programmed values. Based on the signals, the computer then issues commands to various output devices to control the engine and transmission, along with reducing emissions. 1996 and newer vehicles are equipped with second-generation onboard diagnostics (OBDII) systems that put special emphasis on sensor values and emissions.

Maintenance Tips/Suggestions: Sensors do not require regular maintenance or adjustments. Regardless of what a specific sensor measures, all operate within a range of normal values. If a sensor provides a signal outside the normal range long enough, the powertrain control module will set a trouble code, which will usually trigger the SERVICE ENGINE SOON or CHECK ENGINE light. If the light appears, you should have its cause investigated by a professional technician at your earliest opportunity. If the light flashes, the condition is more severe and must be checked out immediately to prevent damage to the catalytic converter.

Gaskets & Sealing

Description: Gaskets and seals are usually named after their location or function on the engine. For example, a head gasket seals the cylinder head to the cylinder block. A rear main seal prevents the area around the rear crankshaft main bearing from leaking oil. Gaskets and seals can be made from a wide range of materials, many times specifically selected for the specific sealing task.

Purpose: Engine seals and gaskets prevent the leakage of oil, coolant and air between mating surfaces, internal passages and the outside of the engine. Seals and gaskets also prevent the entry of dirt and air into the engine.

Maintenance Tips/Suggestions: The best way to care for the gaskets and seals on your engine is to follow a regular maintenance regimen. This includes regular oil and filter changes, engine performance check-ups, and cooling system maintenance. Check your owner’s manual for positive crankcase ventilation (PCV) maintenance intervals and replace the valve as recommended. Oil leaks are one clue of a faulty PCV system. Leaking valve cover gaskets and rear main seals are but a few examples. If the PCV system isn't operating correctly, crankcase pressure can build and force oil past gaskets and seals that would have otherwise been OK. Overheating can quickly cause head gasket failure and warp aluminium cylinder heads. If telltale oil or coolant drips in your driveway or parking place are making you suspicious about a gasket or seal leak, have it investigated by a qualified service technician.

Ignition Components

Description: Ignition components generally include spark plugs, ignition wires, distributor cap, distributor rotor, distributor, ignition coil, ignition module and primary circuit triggering device. For ignition management, the system also relies on the powertrain control module (PCM), which also manages other engine functions. The names and exact use of ignition components varies widely among different makes and models. For example, many ignition systems no longer use a distributor and consequently do not have any of its related parts.

Maintenance Tips/Suggestions: Refer to your owner’s manual for recommended service intervals for the ignition system. An engine that runs rough, bucks, surges, stalls, gets poor fuel economy or fails an emissions test are all signs of a potential ignition system problem. Although some cars now use platinum spark plugs with 170,000-kilometre service life, other parts such as ignition wires still need attention and periodic replacement. If your car exhibits any symptoms such as those mentioned here, you may also experience a glowing CHECK ENGINE OR SERVICE ENGINE SOON light on the dash. If the light appears, you should have its cause investigated by a professional technician at your earliest opportunity. If the light flashes, the condition is more severe and must be checked out immediately to prevent damage to the catalytic converter.

Description: The typical spark plug consists of an outer shell, a connecting terminal, a core, a seat area, a centre electrode, and one or more ground electrodes. Spark plugs used steel/nickel electrodes traditionally, but newer plug designs use electrodes made of precious metals such as platinum or even gold/palladium alloy. These types of electrode materials are much less susceptible to erosion, provide longer life and tend to resist fouling better than their predecessors. Most engines use one spark plug per cylinder, although some engines use two. Spark plugs come in different configurations, such as different threads, seats, "reach lengths", and heat ranges.

Purpose: The spark plug ignites the air/fuel mixture inside the cylinder. This occurs when high voltage, triggered at precisely the right instant, bridges the gap between the centre and the ground electrodes. The end result is an even burning of the air/fuel mixture inside the cylinder. The spark plug also provides a secondary purpose of helping to channel some heat away from the cylinder.

Maintenance Tips/Suggestions: Typical replacement intervals range between 50,000 and 160,000 kilometres, depending on the vehicle and the type of spark plug. Always consult your owner's manual for your specific vehicle. Symptoms of one or more faulty spark plugs include poor gas mileage, a failed emissions test, and rough running/poor acceleration with the engine under load.

A bad spark plug can cause engine misfire, triggering the SERVICE ENGINE SOON or CHECK ENGINE light to appear. If this is the case, it's best to have the cause checked out immediately by a professional technician. This is especially true if the SERVICE ENGINE SOON or CHECK ENGINE light flashes rather than staying steadily lit.

Neglecting these warning signs can cause expensive damage to the catalytic converter, requiring replacement. Always use the correct spark plugs for your vehicle, following the exact recommendations of the spark plug manufacturer for your specific engine and vehicle. Spark plugs should be installed per the manufacturer's recommendations, ensuring the electrodes are gapped properly and tightened sufficiently into the cylinder head.

Tune-Up Performance

Purpose: Technology has not only made the tune-up obsolete; it also requires a fresh approach to understanding what to do with your technological marvel when it’s time for service. Highly sophisticated ignition and fuel systems are now the norm, using one or more onboard computers to control critical engine and transmission management functions. Things that were once handled mechanically are now controlled electronically through the widespread use of onboard computer technology. This has brought about non-adjustable idle speeds and ignition timing, 100,000-kilometre+ spark plug replacements, and the elimination of other traditional, tune-up-related procedures.

Maintenance Tips/Suggestions: While this may yield the initial impression that today’s cars are “set-it and forget-it”, this isn’t the case. Ensuring good performance, fuel economy and emissions may mean that a technician needs to interrogate the vehicle's onboard computer for trouble codes or other system information, analyze exhaust gas readings, or use a “scope” to look at the operating characteristics of the ignition system or other electrical/electronic circuits. If the situation warrants, a technician may even need to reprogram the internal logic of an onboard computer to correct a drivability problem, right in the service bay. Clearly, the manual adjustments of yesteryear have long since been superseded with high-tech engine performance checks by a qualified service technician.

Valve Train Components

Description: The valve train typically includes the camshaft, valves, valve springs, retainers, rocker arms and shafts. On engines with traditional mounting of the camshaft in the cylinder block, the valve train also includes lifters and pushrods. Overhead cam engines may use more than one camshaft per cylinder head. Engines use different valve configurations, such as two, three, four or five valves per cylinder. These various valve arrangements are used for different engine breathing requirements. Some engines also use variable valve timing, which allows the engine to change breathing characteristics under different operating conditions.

Purpose: The cylinder head’s valves, when synchronized with the crankshaft of the cylinder block, allow the engine to “breathe”. In an engine, this means pulling the air and fuel mixture into the cylinder, then pushing the burned exhaust gases out. The better an engine breathes, the more efficient it becomes.

Maintenance Tips/Suggestions: Check your owner’s manual to see if your car requires periodic valve adjustments. Most cars no longer require them, but there are exceptions. To best care for the parts of the valve train, stick to a regular maintenance routine of oil and filter changes and proper cooling system care. Also check the owner’s manual to find out what the maintenance interval is for the timing belt (if equipped). If the timing belt breaks on some engines, it can cause major damage to the valve train and other parts of the engine.

Use the right gasoline for your car as recommended in the owner’s manual. In some cases, the use of premium fuel when it’s not needed can cause deposits on the intake valves, which can cause performance problems. Some symptoms of problems in the valve train include an engine that makes a ticking noise, runs rough, bucks, surges, stalls, gets poor fuel economy or fails an emissions test. Since the same symptoms can also be caused by other engine systems, take your car to a qualified service professional to pinpoint the cause.