There are many reasons a car idles fast, but one common reason is a vacuum leak. Older muscle cars have only two or three vacuum hoses, making finding the leak easy. Newer vehicles have complex vacuum systems to reduce emissions, so leaks are more difficult to find. Popular Mechanics suggests spraying carburetor cleaner on a suspected leak and listening for the engine speed to increase.Know More
An overheating engine increases the speed at which a vehicle idles. The overheating condition often leads to more serious consequences, such as a blown head gasket or a warped head. About.com recommends preventing the potential damage and stopping the fast idle by repairing the cooling system.
Ignition timing affects the idle speed. A timing light quickly reveals problems with vehicle timing and allows the user to adjust it to the manufacturer's recommended specifications.
On vehicles with a powertrain control module, issues with the on-board computer may affect idle. Older vehicles experience similar problems due to problems with the distributor cap, rotor, plugs or wires. About.com suggests testing the control module with a scan tool and replacing defective ignition parts.
A failing alternator may also affect the engine idle. In this case, when the alternator is replaced the speed returns to normal.
A fuel pressure regulator operating incorrectly also increases the engine's idle speed. This is not a do-it-yourself job, so drivers should have a mechanic check the pressure using a fuel pressure gauge and replace if necessary.Learn more about Transmission
Surges during acceleration are usually caused by a fault in the car's fuel management system. Hesitations or stumbles during acceleration may also be linked to problems with the car's secondary ignition system, which includes parts such as a spark plug, rotor and spark plug wires. In most cases, replacing the worn out part fixes the problem.Full Answer >
When a car squeaks during acceleration, it is typically an indication that the fan belt has become loose or worn. A car's fan belt loosens over time and starts squeaking when the bottom section, which has rubber teeth, begins to drag.Full Answer >
The kind of transmission fluid that a car needs depends on the type of transmission that the car has. Automatic transmissions take automatic transmission fluid, and manual transmissions can take a variety of oils.Full Answer >
Dirty transmission fluid causes problems when shifting gears: grinding noises, stalling or misfiring of the engine and overheating of the transmission. These problems are very similar to those caused by low transmission fluid.Full Answer >