Thanks to improved reliability and developments in engine technology and fuel management systems, the process of tuning your car is changing to diagnostics - the science of fault diagnosis.
Diagnosis of automotive faults is sometimes a time-consuming process. Unless you are very lucky and stumble across the fault immediately, the best and ultimately quickest method is to follow a logical test pattern that checks, tests and evaluates all possibilities. The first step in all this is to inspect your car, and in this tutorial we will show you how to give your car a basic inspection.
When you make a basic inspection of a vehicle you should follow a sequence of visual checks and adjustments, and in the process of doing this the problem area can often be quickly diagnosed.
No matter what the problem is, the following checks below are an essential pre-requisite to the use of diagnostic equipment. In many instances, the fault will be revealed during these procedures. Make a careful visual inspection of the following items.
Not all checks will be appropriate for all engines. This basic inspection, though, can save a great deal of valuable diagnostic time.
- Check the engine oil level, oil condition and positive crankcase ventilation (PCV) circuit condition. Maintenance of the lubrication system is particularly important for good engine operation. In catalyst-equipped vehicles, contaminated oil, a poorly-maintained PCV system or an oil-burning engine will contaminate the catalyst in a very short period of time.
- Check the coolant level and coolant system condition. Maintenance of the cooling system is particularly important for good engine operation. An engine that is overcooled or running too hot can affect timing and fuelling actuation.
- Check the automatic transmission fluid level and condition.
- Check the battery condition.
- Check the battery for security.
- Test the voltage of the battery.
- Check the battery cables and connections.
- Use an OBD (On-board Diagnostics) reader to check for any codes.
- Check the drivebelt(s) condition and tension.
- Remove the spark plugs and check the condition. Renew if necessary.
- Check that the spark plug electrode gap is correct.
- Check that the spark plug type is the correct type for the vehicle.
- Check for poor or corroded electrical connections.
- Check for freedom from vacuum leaks from the vacuum hoses, inlet manifold, AFS trunking, oil dipstick seal and rocker cover seal.
- Check the breathing system condition. Clean away accumulated sludge, and ensure that the hoses are clear.
- Check the air filter condition. Renew if it is even slightly dirty.
- Check the exhaust system condition.
- Check the fuel system condition. Check for fuel leaks, and for worn or broken components. If available, the probe from a gas analyser with HC meter can be passed over the fuel and evaporation pipes and hoses. If the HC meter registers a measurement, that component may be leaking fuel or vapour.
- Visually inspect all connections, multi-plugs and terminals. Check for corrosion and loose or displaced terminals.
- Check the throttle body for a carbon
- build-up – usually as a result of fumes from the breathing system. The carbon can cause a sticking or jacked-open throttle, which can cause idle, cruising and other running problems. Carburettor cleaning fluid usually cleans away the carbon nicely.
