Virtual Mechanic

PURPOSE
The air flow meter is a component to allow the velocity of air through it and at the same time it measures the air passing either by a hot wire or a flap connected to a potentiometer.  This value is sent to the computer indicating the quantity of fuel required.  If the air flow meter is a hot wire type it also has a self cleaning process to keep the wire clean from the value interference.

THINGS TO LOOK FOR
The main thing to affect the air flow meter is the large ducting connected to the unit. Also any vacuum leaks will affect the air flow meter value.  A potentiometer may wear its contacts causing a possible flat spot or non start.  Its enemy is a backfire as this will twist the flap making it impossible to move freely.  A quick perusal will determine if the flap is twisted after a backfire thus requiring replacement.  The hot wire type may break, the wiring causing a non start.  The hot wire also has a self clean program.

IS IT EXPENSIVE TO REPAIR?
Either air flow meters are expensive to replace costing around $600.00 depending on the make.

TEMPORARY REPAIR AND LONG TERM REPLACEMENT
Most common types of air flow meters are now reconditioned costing around $300.00.  Make sure you keep your receipt in the Virtual Mechanic folder, as air flow meters do play up from time to time.

 
This article is found in the Virtual mechanic CD Rom
You can download it for the price of a latte, but you will learn not to buy a lemon
By Darren Gow-Brown, Melbourne Australia ©2009

PURPOSE
The EGR valve is design to recirculate exhaust gases but only after idle and before full throttle.  The EGR valve operates mainly on cruising. 

THINGS TO LOOK FOR
Over time the EGR valve may be responsible for poor idle.  EGR valves are sometimes difficult to pinpoint as being the perpetrator of a poor idle.  A quick inspection to see if the needle is moving or if any exhaust gases are coming from the valve may be determined by an electronic fuel injection specialist.
 
IS IT EXPENSIVE TO REPAIR?
The EGR valve can be expensive.  You can try the wreckers but nine times out of ten a new EGR valve is the best way to go as the second hand EGR valve would usually have been on the engine from when the vehicle was new.

TEMPORARY REPAIR AND LONG TERM REPLACEMENT
Most EGR valves are not serviceable.  The EGR valve is specifically designed to eliminate or reduce exhaust gasses entering the atmosphere.  Tampering with an EGR valve may incur fines.

This article is found in the Virtual mechanic CD Rom
You can download it for the price of a latte, but you will learn not to buy a lemon
By Darren Gow-Brown, Melbourne Australia ©2009

PURPOSE
The throttle body position sensor is designed to send a value to the computer to allow the correct mixture of fuel required on that specific value.  The TPS is as a butterfly only it is an electronic butterfly that also sends a signal back to the computer on its position.  The TPS will suffer from clogging up as it has fine circuits or holes around the closing points on one side.  On the inlet manifold side of the butterfly it may be seen as being very dirty.  This must be serviced at least every 50,000kms to ensure a consistent idle.

THINGS TO LOOK FOR
The TPS is a component that should be serviced and an examination will determine its effectiveness.  A check inside the TPS will show a butterfly and on the other side of the butterfly if any muck or, blackness has built up around the venturi, this should be cleaned out with a rag and made spotless as this could affect the idle control.  The difference between a good idle and a poor idle is a clean TPS.
IS IT EXPENSIVE TO REPAIR?
The TPS rarely goes wrong except for the electronic potentiometer, attached to the TPS throttle, may malfunction or the contacts may fail or it may have a flat spot.  These are best calibrated and checked by your local auto electrician.  If the prices quoted for the TPS or the throttle positioner switch is a bit expensive, try the wreckers.  Remember to keep the receipt as the TPS is another component that could go wrong after it has been fitted.
This article is found in the Virtual mechanic CD Rom
You can download it for the price of a latte, but you will learn not to buy a lemon
By Darren Gow-Brown, Melbourne Australia ©2009

PURPOSE
The cold start injector is designed to inject extra fuel when the engine is cold.  This is manipulated by the computer and also by the temperature sensor unit.

THINGS TO LOOK FOR
The cold start injector may leak or malfunction.  An indication of these problems is a hard to start in the morning.  Cold start injectors like other injectors should be ultrasonically cleaned at around 150,000km intervals for the best performance.

IS IT EXPENSIVE TO REPAIR?
A cold start injector is fitted to the vehicle in a different way to the normal injectors therefore it will be a little bit more expensive but ultrasonic cleaning is highly recommended first.

TEMPORARY REPAIR AND LONG TERM REPLACEMENT
Cold start injectors are either cleaned or replaced.  But remember if the cold start injector is not working there may be another component interfering with the cold start injection program.

This article is found in the Virtual mechanic CD Rom
You can download it for the price of a latte, but you will learn not to buy a lemon
By Darren Gow-Brown, Melbourne Australia ©2009

PURPOSE
The injectors are designed to inject fuel and when the fuel injector is energised it should spray fuel.  When this happens the combustion chamber will burn it correctly.  Injectors usually run well for 150,000kms then they should be checked or ultrasonically cleaned to be sure that they are not gummed up and are spraying effectively.

THINGS TO LOOK FOR
It is very difficult to check an injector when fitted to the engine.  One of the indications of a faulty injector is that the vehicle is hard to start in the morning.  This may be the fuel injector leaking or the spray pattern may be causing poor economy or poor performance.  These symptoms are usually noticed at around 250,000kms.

IS IT EXPENSIVE TO REPAIR?
Fuel injectors are not cheap at around $30.00-$40.00 each. 

TEMPORARY REPAIR AND LONG TERM REPLACEMENT
Fuel injectors are repairable in that they can be ultrasonically cleaned, spray tested and pressure tested to be sure that they hold the pressure and not leak under pressure.  These tests are performed by a specialist fuel injection service.  It is important to get a before and after report to prove that there was a difference made when the injectors were cleaned.  The fuel injector may also have a fuel injection cleaner poured into the fuel tank.
This article is found in the Virtual mechanic CD Rom
You can download it for the price of a latte, but you will learn not to buy a lemon
By Darren Gow-Brown, Melbourne Australia ©2009

PURPOSE
The purpose of the fuel injection solenoid resistors are to lower the voltage going to the fuel injection.

THINGS TO LOOK FOR
The fuel injection solenoid resistors are components that rarely go wrong and are used in the early model EFI units.  They are located in a bank situated on the fire wall but they can be checked individually.

IS IT EXPENSIVE TO REPAIR?
These resistors are expensive and can be replaced from your local spare parts outlet or the wreckers.

This article is found in the Virtual mechanic CD Rom
You can download it for the price of a latte, but you will learn not to buy a lemon
By Darren Gow-Brown, Melbourne Australia ©2009

PURPOSE
The carbon canister is designed to soak the fuel vapours from the fuel tank when the engine is turned off or parked in a hot or cold location.   Over time the fuel may expand and the vapours are soaked up by the carbon canister.  When the engine starts the vacuum will draw the vapours, recycle them, and  prevent the vapours from entering the atmosphere. 

THINGS TO LOOK FOR
The carbon canister may be full of petrol if the fuel tank is full and may start to overflow with petrol.  The carbon canister should be checked at least every 20,000-50,000kms to operate correctly.

IS IT EXPENSIVE TO REPAIR?
The carbon canister is rarely replaced.  If it needs to be replaced, go to your local spare parts outlet or the wreckers.

This article is found in the Virtual mechanic CD Rom
You can download it for the price of a latte, but you will learn not to buy a lemon
By Darren Gow-Brown, Melbourne Australia ©2009

PURPOSE
The fuel pressure regulator is a component that regulates the pressure in the fuel rail and also removes the excess pressure and recycles the fuel back into the fuel tank.  The fuel pressure regulator alternates the pressure on idle and full throttle.  This is a physical component.

THINGS TO LOOK FOR
A fuel pressure regulator should have a vacuum hose connected to it.  If not, this will affect the performance of the fuel pressure regulator.  Also a power loss or a non start may occur due to a faulty fuel pressure regulator.

IS IT EXPENSIVE TO REPAIR?
A fuel pressure regular costs around $80.00-$90.00 and is best fitted by your local mechanic.
TEMPORARY REPAIR AND LONG TERM REPLACEMENT
A fuel pressure regulator can be replaced but it has to be proved that the regulator is faulty and this can be difficult.

This article is found in the Virtual mechanic CD Rom
You can download it for the price of a latte, but you will learn not to buy a lemon
By Darren Gow-Brown, Melbourne Australia ©2009

PURPOSE
The cold start injector time switch and a cold start injector both have one thing in common.  They are designed to operate when the engine is cold.  The cold start time switch is a timer designed to turn the cold start injector on to enrich the fuel mixture for an easy start.

THINGS TO LOOK FOR
The cold start injector time switch and a cold start injector enrichment program may decide to malfunction and not operate at all or it continues to run rich when the engine is warm.  Either way, hard to start or the engine cutting out when it is cold could be an indicator that the program is not operating correctly.  Any engine cutting out when it is cold is a problem and needs to be attended to ASAP.

IS IT EXPENSIVE TO REPAIR?
It is difficult to estimate how much it will cost depending on where the problem is but it does require the attention of a specialised auto electrician.

TEMPORARY REPAIR AND LONG TERM REPLACEMENT
If the cold start injector is causing a problem by cutting out and is very difficult to start, try holding the throttle a third of the way and don’t pump it but crank the motor.  Once you start it, get it warm before you drive off.  This is a short term remedy only.

This article is found in the Virtual mechanic CD Rom
You can download it for the price of a latte, but you will learn not to buy a lemon
By Darren Gow-Brown, Melbourne Australia ©2009

PURPOSE
The purpose of coil and spark plug leads is to deliver high voltage spark from the coil to the spark plugs.  As ignition leads carry a high voltage it is very important to use caution when handling these leads with the ignition on or with the engine idling.  Ignition leads are made of fibres to reduce the possibility of radio wave interference.  Due to the high demand of these leads they may fail at any time. 

THINGS TO LOOK FOR
Ignition leads either deliver high voltage or they start to isolate and end up open circuiting thus creating a misfire.  This shouldn’t be ignored as a misfire may be causing damage to the exhaust system.  Also it may cause damage to the ignition coil as the high voltage can create a carbon track from the secondary lug to the primary lug destroying the coil.  A faulty lead may make the engine difficult to start.  All leads should be tested for resistance. 

IS IT EXPENSIVE TO REPAIR?
Ignition leads should be purchased in a set as they are replaced all at once.  When purchasing leads buy a well-known brand as even new leads can be faulty and testing is required before fitting to make sure that the leads are not faulty. 

TEMPORARY REPAIR AND LONG TERM REPLACEMENT
Testing or fitting any leads must be carried out one at a time as ignition leads are designed to fire in a firing order.  For this reason it is best to remove and replace one lead at a time to prevent messing up the firing order, thus creating a potential backfire.

This article is found in the Virtual mechanic CD Rom
You can download it for the price of a latte, but you will learn not to buy a lemon
By Darren Gow-Brown, Melbourne Australia ©2009