Engine Management Systems
Most of today's cars are controlled by electronics with more devices being developed and fitted to cars each year. The most important one to be built into cars since the late 1980s has to be the Engine Management System.
It is the Engine Control Module (ECM), or the "brain", that controls the fuel supply and the ignition by combining the two separate functions into one main system. The brain controls the whole of the combustion process, making the engine more efficient and less polluting than ever before, especially when fitted with a catalytic converter.
The downside is that if the ECM does go wrong it can be very difficult to diagnose and expensive to rectify. This is when you will need a fully trained technician, since it requires specialist knowledge and test equipment to diagnose any faults that may be in the system.
The system works by using sensors located throughout the engine. These sensors measure the speed and the temperature of the intake air as well as the speed and position of the crankshaft. This information is then processed and the end result is that of the fuel being delivered to the engine in precisely the correct amount at any given time.
This makes the engine more efficient, economical, less polluting and more powerful. The fuel is injected into the engine at high pressure and at a calculated rate by electronically controlled injectors. The ignition is also controlled by the brain to allow for movement in ignition timing which will produce better combustion so more of the fuel entering the engine can be burnt.
Air Flow Meter
This device measures the amount of air being drawn into the engine so that the fuel delivery can be calculated to mix with the air in the required quantities.
Mass Air Flow Sensor
This does a similar job as the air flow meter.
Manifold Absolute Pressure Sensor
This tells the brain how much load the engine is under by indicating the amount of vacuum in the inlet manifold.
Throttle Position Sensor
This is the sensor that constantly measures the movement and position of your accelerator pedal so the brain knows if you are cruising with light throttle or accelerating hard with full throttle.
Knock Sensor
The knock sensor is a unit that sits on the engine block and listens for "pinking"; a metallic rattle caused by overly advanced ignition timing that can damage the pistons. When pinking occurs the sensor sends a voltage to the brain so the timing can be adjusted to prevent damage.
Oxygen Sensor
This sensor is fitted in the exhaust and measures the oxygen content of the burnt gases. If the oxygen levels are incorrect, the brain is instructed to vary the fuel supply until it reaches the desired level. This is usually referred to as the Lambda. Later vehicles have two sensors, one before the catalytic converter and one after, so gases can be monitored and the effectiveness of the converter can be measured.
Catalytic Converter
This is a filter-like furnace that burns toxic gasses that are present in the exhaust to reduce harmful emissions.
Temperature Sensors
These sensors measure the engine coolant and intake air temperatures. If the engine is cold then the brain will know to open the injectors for a longer period to increase the fuel delivery, much like a choke on a carburettor.
Crankshaft Position Sensor
This sensor is actually the key part of the system. If it doesn't sense the crankshaft moving the system will not even operate. It serves to indicate the crank position and speed at which the engine revolves.
Camshaft Position Sensor
This sensor works like the crank sensor but gives a secondary reference point for the position of the camshaft and a signal for limp home mode if the crank sensor fails.
Limp Home Mode
This term describes an average setting programmed into the brain, so the engine management system can work to get you home if one or more of the sensors fail. Normally you will find the engine will only rev to 2500 rpm when this happens.
Caring for your Engine Management System
Do not use jump leads as this can cause a spark at the battery terminal (SPIKE) that can damage your engine control unit. If you use another garage for servicing, ask them to clear the brain’s memory when re-setting the service light, as disconnecting any sensor will log a fault code in the brain to say there has been a problem.
When trying to diagnose a fault later, all previously stored faults will show on the equipment, confusing the technician and extending the time taken to pinpoint the fault. Engine Management Systems are very complicated electronic systems and any work carried out by untrained personnel can result in unnecessary damage and expense.
Diesel Engine Management
Due to improvements in engine design and rapid-acting electronics, diesel engines are making more of a stamp on the automotive industry. Many of the original gripes with diesel engines have been eradicated by the introduction of 'common rail' technology; an injection system that injects fuel at high pressures allowing the fuel to burn more efficiently and with much cleaner exhaust emissions. This has replaced the old 'distributor pump' systems and enhances the engine's efficiency.
The improved electronics also monitor what the engine is up to, adjusting the injection timing and dosage with complete accuracy. As a result, there is virtually no operating smoke and the combustion noise is reduced to the levels of petrol-powered engines. The knocks and rattles associated with diesel engines are significantly fewer with 'pilot injection'; a tiny explosion of fuel before the big bang of the turnover. This allows for a gradual increase in temperature rather than a sudden one, making for a smoother start.
Further to this, Volkswagen has a 'pumpe düse' or 'pump metering' system that combines the high-pressure pump and the injector. It has the capacity to generate higher injection pressure than common rail and produce very little exhaust smoke, but has been criticised for not being as quiet as most popular common rail systems. Motorsave, under the watchful eye of BOSCH, are able to service and repair all of these diesel engines with the added guarantee of quality parts, workmanship and expert advice. As with all of our other services, you will be consulted on what needs to be done and how much it will cost. This way you know where you stand, we know that you feel confident with our proposal and we both know what needs to be done and for what price.
Auto Electrical Fault Finding
Auto Electrical Diagnostics
Motorsave have been specialising in auto electrical diagnostics since 1988. We use our knowledge and experience to quickly diagnose and rectify a wide range of faults including charging, starting, central locking, lighting, windows, alarms and more.
Annual training from BOSCH guarantees we keep up to date with the latest sophisticated diagnostic systems such as smart charging and CANbus systems. CANbus is a system that replaces miles of wiring loom with a two wire system that sends signals between control units which operate lights, wipers, indicators etc. If your vehicle was manufactured after 2001 you are probably using a CANbus system.
Electronic Stability Program (ESP) / Antilock Brake System (ABS)
The ABS braking system has given drivers better vehicle stability and straight-line braking under an emergency since its introduction in around 1978. They didn't escape their initial teething troubles however, and it wasn't until various improvements had been made that ABS became a standard feature on two thirds of all manufactured cars.
The stage beyond ABS has been ESP (electronic stability program) and we're celebrating ten years of this technology this year. ESP is a braking system that prevents skidding in critical conditions and recent studies have shown that ESP can reduce the number of serious accidents on the road by up to half.
Airbags (SRS)
According to some people, airbags are the most important safety device introduced since the seatbelt. This feature has been introduced into vehicles in the UK and has reduced the number of serious injuries resulting from road accidents dramatically. Other ‘safety restraint systems' (SRS) found in modern vehicles are seatbelt pre-tensioners, side impact airbags, inside rear door pillars and even airbags in the doors themselves.
Airbags work through the application of controlled explosives. As a vehicle is involved in an accident above 20 mph a sensor will trigger the airbags and other SRS systems immediately. The most common airbag is situated in the middle of the steering wheel along with the inflator. When the on-board sensors have received information of an immediate deceleration of around 5 mph and any impact to front, sides or rear of the car a compressed gas capsule is released. The inflation process of the airbag takes less than one second to deploy and restrain the occupant.
Airbag Safety
Remember that babies, small children and other frail or weak persons must not be positioned near an airbag. Some systems can be manually turned off, but this should only be done in accordance with the manufacturer’s vehicle handbook or by a qualified technician.
If the airbag has been deployed, it is imperative that the system is reset by qualified and experienced technician who would have the necessary skills and equipment. As the safety of you and your passengers is paramount, it is vital that the work is done properly. Do not allow untrained or unqualified personnel carry out repairs on SRS systems. The chance of personal injury due to system failure is not worth risking.
After an accident in which the airbag has not been deployed you should still take the car to your nearest garage immediately to have the system checked. If this is not done, the system may not work correctly in the event of another accident when the airbag will be required. If the SRS fault warning lamp illuminates on the instrument panel, take your car in for the fault to be diagnosed as soon as possible.
Air Conditioning
Around 85% of all new cars sold are fitted with air-conditioning as a standard feature. Regular servicing of your air conditioning system is important and should not be left out of your usual vehicle service requirements. It is recommended that car owners have their air-conditioning units fumigated every twelve months and completely cleaned and serviced every two years.
Many people may not realise that the car will use the air conditioning system to remove humidity when defrosting the windows. So most air conditioning systems tend to be used more often than just in the summer months.
Your air-conditioning unit loses on average fifteen percent of its refrigerant capacity every year. In addition to this, a poorly performing system will cause the engine to use more fuel and, over time, the system will build up fungus, bacteria and micro-organisms. These will tend to grow inside the evaporator cove and can cause unpleasant smells and allergic reactions such as sneezing, coughing and irritation to the eyes.
Pollen filters
These should be replaced as specified by the manufacturer but checked when the system is serviced.
Make sure that you use your air conditioning system for at least ten minutes every week. This will circulate gas and important oils and reduce the amount of gas that is lost through dry seals which can leak. On hot days you should close all the windows, turn the temperature down and select recirculation on the controls to trap the cool air in the car. When using the system as a dehumidifier, choose your temperature, select de-mist and make sure recirculation is turned off and the air conditioning is on - this will clear the windows much faster.
Motorsave offer air-conditioning cleaning as part of the complete servicing commitment; speak to one of our team today about having your system fumigated.
- partly worn tyres are more likely to experience punctures – particularly in wet weather conditions
- rapid front tyre deflation will create an under-steer effect which is easier to control than over-steer (the effect produced by a rear tyre deflation)
