Common Faults

Electric fuel pumps

Most fuel pumps on modern cars are now located inside the fuel tank itself, also refered to as an in tank fuel pump.
If you dont have fuel pressure testing equipment available here is a quick simple test.
Firstly locate the whereabouts of the fuel tank, then get somebody to turn on the ignition without actually starting the car, listen for the pump buzzing, it should buzz /pump for a few seconds only ( this is to get the pressure to the fuel system ready for starting the engine) if you cannot here a buzzing sound and you have already checked the fuse related to the electric in tank pump then there is a very good chance that your pump has failed.

Please also note the following : Fuel Pump Problems 

Fuel pump problems, such as inadequate pressure or a malfunctioned equipment, are often traced to poor maintenance or handling of the vehicle. The risk involved is maximum if you are guilty of using the vehicle in spite of low fuel, or using contaminated fuel for that matter. Inadequate pressure will either prevent the car from starting, or cause the engine to start and quit while running. If the pressure is normal, but volume is inadequate, the engine will work, but other problems, like power and inadequate supply of fuel to the engine, may arise. In case of bad fuel pump, however, the engine will not start at all.

In modern vehicles, the electric fuel pump is programmed to stop functioning in the event of an impact. This is done to prevent fuel leakage and further damage in case of accident, i.e., if the car collides with something or rolls over. In cases like these, car owners misdiagnose the problem and opt for the replacement of fuel pumps. Though the fuel pump in itself is not very expensive, service charges definitely are. And therefore, it is wise to ensure that the problem lies with the fuel pump before you opt to get it changed.

Abs Brake Sensors
What does an ABS Sensor do?
The anti-lock braking system uses an ABS or wheel sensor 
to monitor the wheel speed and send this information to the 
ABS computer. The ABS computer uses this information to 
prevent the brakes from locking during an emergency stop. 
If wheel speeds are not equal the computer modulates the 
anti-lock feature until the speeds are equalized.
Where are these sensors located?
The ABS sensor is typically located in each wheel hub/
rotor on a four channel ABS system. Some rear wheel 
drive applications have the sensor mounted in the rear 
What are the common causes of failure? 
Typically these sensors will fail as a result of clogging from 
metallic debris, brake dust or dirt due to exposure to the 
harsh elements.

What does a Camshaft/Crankshaft Position Sensor do? 
The Camshaft sensor determines which cylinder is firing to establish injector synchronization and coil firing sequence in DIS systems. Crankshaft sensors set ignition timing, supply the RPM signal, and determine engine speed. 

Where are these sensors located? 
The Camshaft Position sensor is typically located in the cylinder head of the engine and has a cylindrical portion that inserts into the head. The Crankshaft Position sensor is normally located in the timing cover or on the side of the block with a cylindrical portion that inserts into the block. 

Crankshaft and Camshaft position sensors

A camshaft and crankshaft position sensor is used on vehicles that do not have distributors. The sensors tell the computer on the vehicle which cylinder is firing and times the firing of each cylinder to ensure the automobile engine operates efficiently. When the camshaft position sensor fails or is bad, the automobile develops symptoms such as not starting, misfiring or hesitating during acceleration.

Oxygen Lambda Sensors
The most popular method used by vehicle manufacturers to reduce engine emissions is the three-way catalyst (catalytic converter). This device has the ability to take the three main toxic gases produced by an engine which are carbon monoxide (CO), oxides of nitrogen (NOx) and hydrocarbons (HC) and convert them to considerably less harmful, non-poisonous gases: carbon dioxide (CO2), water (H2O) and nitrogen (N2).

To carry out this conversion of gases efficiently the catalyst must operate within a specified temperature range but also be provided with exhaust gases that are within certain very tight tolerances dependant predominantly on air/fuel ratio. The precise control required to operate this system is provided by the use of an exhaust gas oxygen (Lambda) sensor installed upstream of the catalyst. A Lambda sensor has the ability to precisely measure the air/fuel ratio present in exhaust gases. By sending a signal to the control unit it can initiate a change to keep the fuelling system operating within the very tight tolerances required. This is known as a closed-loop control system.

To further improve control of exhaust emissions most vehicles produced after 2000 have an additional Lambda sensor fitted down-stream of the catalyst that monitors the performance of the catalyst itself.
When should I replace the oxygen sensor?
     Usually, oxygen sensors require replacement around 60 to 100K miles. You should check the owner’s manual or repair guide for the recommended mileage for your car. Most modern cars have a service light or gauge that lights up when the preset mileage has been reached. This light is usually triggered by a few different things, such as a mechanical mileage counter or by counting a certain amount of turns of the key in the ignition. In these cases, the light is merely a reminder to service the sensor. Be sure not to confuse a service reminder light with an actually failure light. A failure light is a light that only illuminates when the sensor actually fails. Check the owner’s manual or repair guide if you are in any doubt as to whether or not the light is a failure light or service light.  It is not always necessary to replace the sensor at the factory recommended mileage however. These are usually just a service recommendation. Naturally, parts do wear out and fail over time, so it’s always a good idea to practice preventative maintenance on your car.
What are the symptoms of a bad oxygen sensor?
     The biggest indicator of a faulty oxygen sensor is a noticeable decrease in fuel economy, along with a rich mixture. Now, this does not automatically indicate that the sensor has failed. Be sure to check all vacuum hoses for leaks as well as the ignition system, check the plugs, (are they fouled?) check the rotor, distributor cap, points, spark plug leads, and condenser (check all of these where applicable) Vacuum leaks and ignition problems are notorious for causing fuel economy problems. It’s a good idea to inspect and re-new the vacuum hoses every couple of years anyway. Other symptoms of a faulty sensor are a loss of power, (particularly when accelerating from a stand-still), overheating, and spark plug fouling, both of these are due to an increased rich or lean running condition. 
     Most modern cars nowadays come with sort of a built in troubleshooting guide that can help you diagnose if the sensor is bad. There is usually a port or connector where you can plug in a computer and extract codes from the fuel injection computer. In the case of most new cars, when an error occurs, it generates a code and stores it. Using the computer, you can extract the code from the fuel injection computer. This is invaluable in determining not only a bad oxygen sensor, but all sorts of other problems as well. In many cases, this can tell you if the sensor is bad, however if it does not, keep reading, the steps below will go over how to test the sensor.

Idle Air Control Valve Information
An idle air control valve, also called an IAC valve, is found in every vehicle and is located inside of the throttle body. When a car idles at a red light or while parked, the idle air control valve regulates the amount of air that circulates in the engine, which keeps the engine at a steady RPM and prevents rough idling. When an air control valve goes bad due to either carbon build-up or getting stuck, there are a few obvious symptoms.
Low RPMs
A bad idle air control valve will prevent adequate air flow to the engine and will result in increasingly lower RPMs when idling. The number of RPMs, while idling, will vary a bit based on the individual vehicle but is generally considered low when below 800 RPM. The RPMs will increase to normal levels when the accelerator is pressed.
As the air control valve becomes increasingly clogged, the engine RPMs, while idling, will continue to drop until the vehicle stalls. This problem can usually be identified by applying the gas. When the vehicle is about to stall, pressing the accelerator will cause the RPMs to increase and will keep the car running. If the pedal is released, the RPMs will quickly drop, and the vehicle will stall. Sometimes, depending on how badly the idle air control valve is clogged, the vehicle may run correctly when the accelerator is pressed, but then sputter or stall when decelerating.
Rough Idle
If the idle air control valve has gone bad and no longer regulates the flow of air into the engine, typically due to the IAC being stuck open, the vehicle will idle roughly. A rough idle is characterised by shaking, vibrating and shuddering while the car is on but not moving. A rough idle due to a bad intake air control valve will eventually result in stalling immediately after starting the vehicle.