Hard Starting: This is the most common form of car trouble. It's usually due to some unperformed maintenance. If the starter cranks the engine, the electrical system is probably okay. The culprit could be a starting sensor (on fuel injected models) or the choke mechanism (on engines with carburetors). Frequently, starting failure can be traced to an electronic component or a computer controlling the ignition system.
Knocking: The noise generally is heard when the engine is under load, such as when accelerating or climbing a hill. While it often may be caused by a thankful of interior gas, ignition knock frequently is a sign your engine needs attention. It also can be caused by a buildup of carbon inside the engine. Lake-model cars are equipped with a knock sensor which 'hears' the sound and makes corrective adjustments. But it cannot compensate for a severe malfunction, a condition that can affect engine performance and even damage the engine.
Stalling: This can be caused by incorrect speed adjustments, a malfunctioning sensor or switch, dirty fuel-system parts, worn spark plugs, or other engine deficiencies. Does it stall when hot? Cold? With air conditioning on? To make diagnosis easier, make note of when it happens and advise your technician.
Power Loss: How long since the fuel filter was changed? A dirty filter is a common cause of power loss. As noted under "poor gas mileage", there can be many causes of this condition, most of which can be located with a diagnostic procedure.
Poor Gas Mileage: By keeping a regular check of gas mileage (miles driven divided by gallons used); you can tell if your engine is losing efficiency. Increased gas consumption may be accompanied by other symptoms listed in this section. Note that poor gas mileage also may be due to: under inflated tires, engine running too cold, transmission malfunction, dragging brakes, misaligned wheels.
Dieseling: This also is known as "after-run". The engine keeps chugging and coughing for several seconds after the ignition is shut off. Causes can range from inferior gas to excessive idle speed. Carbon in the combustion chamber also may cause dieseling.
Exhaust Odor: The smell of rotten eggs comes from the catalytic converter, part of your car's emissions-control system. The odor can be due to an engine problem or it can be a sign that your car's catalytic converter is malfunctioning.
Rough Running: A malfunction in either the fuel or ignition system can cause an engine to run rough. It also can be due to an internal engine condition, such as a bad valve or piston. Does it occur when idling? When accelerating? At all speeds? Your best bet: have a qualified technician perform diagnostic and tune-up services as needed.
Article Source: http://EzineArticles.com/903077