How to Adjust a Car Idle

How to Adjust a Car Idle

As cars get older and accrue more mileage, the idle speed of an automobile may be higher or lower than it needs to be, either wasting precious fuel or causing the car to stall out. Adjusting your idle is relatively easy, with the same basic procedure for any car. However, be sure to check the specifications for your car before doing any of your own maintenance.

Things You'll Need

Screwdriver

Instructions

Start your car and allow it to cycle through at least one period of going through a higher RPM rate. This will ensure that the engine is completely warmed up and you will be able to adjust the idle properly. It is important to allow the engine to warm up because you will be driving your car mostly at that condition. While the engine is warming, you can pop the hood of your car and prop it open.

Locate the throttle body. You can recognize it by tracing your air intake hose as it exits the air filter. The next part that the air hoses connect to is a metal part called the throttle body. Look on the sides of the throttle body until you locate a screw or a rubber casing that houses a screw. This screw is how you adjust your idle.

Remove the rubber casing for the idle switch by prying it off with a screwdriver. This casing is usually installed by manufacturers but is not needed for the performance of the idle switch. If your idle has been adjusted before, then there will be no covering over the screw.

Disconnect the idle air adjustment valve, which regulates whether the idle opens or closes depending on the air intake. Disconnect the valve by locating the electrical connector behind the throttle body. Be careful not to touch any hot engine parts while working on the idle.

Turn the idle screw, now exposed from the protective rubber coating, in order to adjust the idle. Loosen the screw in a counter-clockwise fashion to increase idle speed or tighten it in a clockwise manner in order to decrease the idle speed. Ideally, you will want the idle to rest at 650 RPM.

Reconnect the idle air controller valve electrical connection. Lower the hood and turn your car off.

High Idle Causes

High Idle Causes

A high idle in your car can cause you to worry. When the engine seems to rev up on its own while you are at a standstill, you may wonder if it's a sign of trouble that needs the attention of a mechanic. The answer to that question depends on the cause of the high idle. Some causes are harmless, while others can indicate the need for a repair.

Faulty Fuses

Most modern car engines control the engine idle speed through a motor called an IAC (idle air control) motor. One of the leading causes of IAC motor malfunction is a blown or faulty fuse. A malfunctioning fuse in any of the electronically controlled components including the air bag system can disrupt the function of the IAC motor and lead to a higher idle speed than usual.

Computer Malfunctions

Computers control a modern car's engine and transmission, its brake system and its airbag system. If the fuses are fine, the computer system itself in one of these components might be malfunctioning. If that's the case, that might be the source of the high idle speed in your engine.

In some cars, the powertrain control computer can misinterpret the information it receives about the idle speed, leading to higher idling speeds. Cold weather can trigger this problem, and it usually corrects itself once the engine is warmed up.

Leaking Vacuum

The IAC motor works with a vacuum port to control the engine's idle speed. By opening and closing a valve to the vacuum port at set intervals, the IAC motor sets the idle speed. If the seal on the vacuum port is leaking, that will interfere with the overall function of the IAC and may lead to high idle speeds. Often it is the hoses connected to the vacuum system that become damaged, leading to an imperfect vacuum.

Malfunctioning Throttle

The throttle system in the vehicle might not be working properly, which can cause engine stalling or high idling. Common causes of a throttle malfunction are a buildup of dirt and contaminants in the engine's secondary air intake or a cracked air intake tube.

IAC Motor Malfunction

The IAC motor itself may not be working properly. A short circuit in the motor can trigger high idle problems. Sometimes IAC motors develop high resistance in the circuitry, which slows the reactions of the IAC and can lead to idling problems.

How to Rewire a Car Lighter Adapter Plug

How to Rewire a Car Lighter Adapter Plug

Portable electronic appliances typically come with 12-volt adapters and patch cords that enable such appliances to be used inside vehicles. In the United States, production of 12-volt automobile plugs is standardized under "UL standard 2089," which covers plugs and patch cords that insert into cigarette lighter receptacles. A 12-volt car lighter adapter plug is easy and convenient to use, but can sometimes become defective due to abuse or misuse. If you know how to rewire a defective car lighter adapter plug you can save yourself some cash.

Things You'll Need
Diagonal pliers
Wire stripper
Soldering gun
Solder wire


Instructions
Cut the cord attached to the lighter plug about 2 inches below the plug, using diagonal pliers. Remove about 2 inches of outer covering from the tip of the patch cord, using diagonal pliers. Strip off 1/2 inch of insulation from the tip of the two inner wires (positive and negative), using a wire stripper.

Look at the plug. Observe the two retractable metal fins protruding on each side of its cylinder, and the retractable metal nipple at its tip. Note that the side fins are negative conductors, and that the tip is the positive conductor of the 12-volt circuit.

Hold the plug cap in your right hand, hold the cylindrical body in your left hand, and twist the cap counterclockwise to unscrew the cap from the plug's cylindrical body. Find the holding screw along the adapter plug's cylindrical body, and unscrew it with a screwdriver. A lighter plug is typically split lengthwise along its center into two identical halves. Open the cylindrical body to reveal the metal fins and nipple inside, including a small spring that pushes the retractable metal nipple.

Note the order in which the metal conductors and spring are arranged inside the plug's cylindrical body. Remove the existing wires attached to the metal nipple, and to the metal fins, by cutting the wires using diagonal pliers.

Loop the stripped end of the positive wire (red, or black with white stripe) around the base of the metal nipple (positive terminal), and solder the copper wire to the metal nipple, using a soldering gun and solder wire.

Wrap the stripped end of the negative wire (black, without stripe) around the base of the metal fins. Fasten the wire onto the fins, using soldering gun and solder wire. Replace the metal nipple and metal fins inside the plug, and reassemble the plug in the same arrangement as you had found them earlier. Make sure that the positive and negative wires do not come in contact with each other.

Turn on your vehicle's ignition switch. Insert the car lighter adapter plug into a 12-volt receptacle on your vehicle's dashboard, and turn on your appliance to test the connection.