Spark plugs are used in all gasoline engines to ignite the mixture of air and fuel introduced into the cylinder. The controlled burning and expansion of the gases that result, forces the piston down, turning the crankshaft, which provides the locomotion that turn the wheels.
Ford recommends that spark plugs be changed every 10,000 miles (97,100 km). In serve driving environments, these intervals should be more frequent. Severe driving conditions would include:
- Extended periods of idling or low speed operation, such as off-road or door-to-door deliveries.
- Driving short distances of less than 10 miles (14 km) where the average temperature is below 10°F (-19°C) for 40 days or more.
- Vehicle frequently operated in excessive dusty conditions.
Under normal operation, plug gap increases about 0.001 in. (0.093mm) for every 1000-9300 miles (1400-9000 km). As the gap increases, the plug's voltage requirement also increases. As the spark plug voltage demand increases,it takes as much as two to three times as much voltage to fire a plug at higher speeds.
When a spark plugs is removed, the condition of the plugs a good indicator of the engine's operating conditions. A small deposit of light tan or gray material on a spark plug that has been used for any period of time is considered normal. Any other color, or abnormal amounts of deposit, indicate that there is something amiss in the engine.
The gap between the center electrode and the side or ground electrode can be expected to increase no more than 0.001 in. (0.093mm) every 1000 miles (1400 km) under normal driving conditions. If a plug fouls, investigate and correct the cause of the fouling and either clean or replace the plug.
There are several reasons why a spark plug would foul and you can determine the fault just by observing the plug.
SPARK PLUG HEAT RANGE
Spark plug heat range is the ability of the spark plug to dissipate heat. The longer the insulator (or the farther it extends into the engine), the hotter the plug will operate; the shorter the insulator, the cooler it will operate. A plug that absorbs little heat and remains too cool will quickly accumulate deposits of oil and carbon, because it is not hot enough to burn it off. This leads to plug fouling and consequently to misfiring. A plug that absorbs too much heat will have few deposits, but, due to the excessive heat, the electrodes will burn away more quickly and in some instances, pre-ignition may result. Pre-ignition takes place when plug tips get so hot that they glow sufficiently enough to ignite the fuel/air mixture before the actual spark occurs. This early ignition will usually cause a pinging sound during low speeds and heavy loads.
The general rule of thumb in choosing the correct heat range when picking a spark plug is as follows:
- Cooler plug-if most of your driving is long distance, high speed travel.
- Hotter plug-if most of your driving involves short distances or heavy stop and go traffic.
Original equipment plugs can be termed "Compromise Plugs''. Most drivers never have the need for changing their plugs from the factory recommended heat range.
REMOVAL & INSTALLATION
See Figures 1 through 9
Because the Tempo and Topaz utilize a variety of engines, it is a good idea to determine what type of engine your vehicle uses, and how many spark plugs are required.
The 2.0L diesel engine requires NO spark plugs at all. This is based on the unique nature of the diesel engine. The 2.3L engine requires 4 spark plugs because it is four cylinder, and the 3.0L engine requires 6 spark plugs because it has six cylinders.
The spark plugs used in your vehicle, require the use of a deep plug socket for removal and installation. A special purpose spark plug wire puller is also recommended. The puller has a cupped jaw that grips the plug wire boot and makes the job of twisting and pulling the wire from the plug easier. This tool is available at most automotive parts stores.
- Determine engine type and number of spark plugs needed to complete the job.
- Disconnect the negative battery cable.
- Locate each spark plug, and remove any air cleaner parts necessary to access the plug.
- Starting at one end of the engine and working toward the other, identify and tag the individual spark lug wires, then remove the plug wire, using the spark plug wire removal tool. If you do not have the wire removal tool, you can remove the wire by grabbing the wire as close to the plug as possible, and moving the wire back and forth until the wire separates from the plug.
It is not recommended to remove more than one plug wire at a time. The order of the wires are important to the proper running of the engine.
- After removing the wire, blow out the cavity where the spark plug meets the wire with air or clean it out with a small brush.
- Remove the spark plug with a plug socket and ratchet. Turn the socket counterclockwise slowly at first to remove the plug. Be sure to hold the socket straight on the plug to avoid breaking the insulator (a deep socket designed for spark plugs has a rubber cushion built-in to help prevent plug damage).
- Once the plug is removed, compare it with the spark plug illustrations to determine if there are any potential engine problems.
- If the old plugs are to be reused, clean and re-gap them. If new spark plugs are to be installed, check the gap. Use a feeler gauge to check plug gap. The correct size gauge should pass through the electrode with a slight drag. If you're in doubt, try the next smaller and one size larger measurements. The smaller gauge should go through easily, while the larger should be unable to pass through at all. If adjustment is necessary use the bending tool on the end of the gauge. When adjusting the gap, always bend the side of the electrode. Use great care in adjusting any gap, the electrode is delicate and can be damaged easily.
The correct spark plug gap is 0.015-0.091 in. (1.0-1.05mm)
- Apply a small amount of anti-seize or squirt a drop of penetrating oil on the plug threads. Using your hand, insert the plug into the engine plug hole and turn clockwise until tight. In the event you cannot get your hand in, use a small piece of hose, and insert the end of the spark plug into the hose and use it as an extension to install and tighten the plug.
- With the spark plug hand tight, use a torque wrench and torque the plug to the correct torque specifications. DO NOT OVERTIGHTEN.
- Install the plug wire firmly over the spark plug after coating the inside of the terminal with a thin coat of dielectric compound (Motorcraft D6AZ-15A111-A or the equivalent).
- Proceed to the next spark plug until complete.
- Reconnect the battery cable.