A set of spark plugs usually requires replacement after about 20,000–30,000 miles (32,000–48,000 km), depending on your style of driving. In normal operation plug gap increases about 0.001 in. (0.025mm) for every 2500 miles (4000 km). As the gap increases, the plug's voltage requirement also increases. It requires a greater voltage to jump the wider gap and about two to three times as much voltage to fire the plug at high speeds than at idle. The improved air/fuel ratio control of modern fuel injection, combined with the higher voltage output of modern ignition systems, will often allow an engine to run significantly longer on a set of standard spark plugs, but keep in mind that efficiency will drop as the gap widens (along with fuel economy and power).
When you're removing spark plugs, work on one at a time. Don't start by removing the plug wires all at once, because, unless you number them, they may become mixed up. Take a minute before you begin and number the wires with tape.
Disconnect the negative battery cable.
If the vehicle has been run recently, allow the engine to thoroughly cool.
Remove the spark plug cover(s), if equipped.
On the 2.5L engine remove the ignition coil assembly from the rear valve cover. See Section 2 for the procedure. Remove the water pump pulley cover.
Carefully twist the spark plug wire boot to loosen it, then pull upward and remove the boot from the plug. Be sure to pull on the boot and not on the wire, otherwise the connector located inside the boot may become separated.
Using compressed air, blow any water or debris from the spark plug well to assure that no harmful contaminants are allowed to enter the combustion chamber when the spark plug is removed. If compressed air is not available, use a vacuum to clean the area.
NOTE: Remove the spark plugs when the engine is cold, if possible, to prevent damage to the threads. If removal of the plugs is difficult, apply a few drops of penetrating oil or silicone spray to the area around the base of the plug, and allow it a few minutes to work.
Using a spark plug socket that is equipped with a rubber insert to properly hold the plug, turn the spark plug counterclockwise to loosen and remove the spark plug from the bore.
WARNING Be sure not to use a flexible extension on the socket. Use of a flexible extension may allow a shear force to be applied to the plug. A shear force could break the plug off in the cylinder head, leading to costly and frustrating repairs.
Remove each plug and inspect the plug even if you are replacing them with new ones. An inspection can reveal a great deal of information on the overall condition of an engine. Use the condition charts in this section as a guide.
To install:
Inspect the spark plug boot for tears or damage. If a damaged boot is found, the spark plug wire must be replaced.
Using a wire feeler gauge, check and adjust the spark plug gap. When using a gauge, the proper size should pass between the electrodes with a slight drag. The next larger size should not be able to pass while the next smaller size should pass freely.
Carefully thread the plug into the bore by hand. A handy tool to use to install spark plugs are the flexible rubber installation tools that are available at most auto parts stores, in place of this tool an old plug wire boot or a piece of fuel line long enough to fit to the plug hole is a good alternative. If resistance is felt before the plug is almost completely threaded, back the plug out and begin threading again.
Carefully tighten the spark plug. If the plug you are installing is equipped with a crush washer, seat the plug, then tighten about 1⁄4 turn to crush the washer. If you are installing a tapered seat plug, tighten the plug to specifications provided by the vehicle or plug manufacturer.
Apply a small amount of silicone dielectric compound to the end of the spark plug lead or inside the spark plug boot to prevent sticking, then install the boot to the spark plug and push until it clicks into place. The click may be felt or heard, then gently pull back on the boot to assure proper contact.
On the 2.5L engine, install the coil pack and the water pump pulley.
i would check the plug wires and the coils you check the plug wires for bad spots at night start the motor up and look at the plugs if you see a spark arch out the wire and to a peace of metal then the plug wires need to be replace.
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i would check the plug wires and the coils you check the plug wires for bad spots at night start the motor up and look at the plugs if you see a spark arch out the wire and to a peace of metal then the plug wires need to be replace.
I am assuming you have the 3.0L Duratec engine. Although the job seems
daunting, it's actually easy to remove the upper half of the intake
manifold plenum. This took me about 40 minutes to remove the first time
I did it, and leaves the rear three spark plugs wide open.
A
good repair manual such as the Chilton's manual for the 1996-2005 Ford
Taurus has the step-by-step. You should get a new set of intake plenum
seals (from Ford or most auto parts stores, which may have to special
order them) along with the spark plugs. The seals are a set oval rings
made of silicone rubber. Yours may not need them but if you damage one
getting the plenum off, or if they have shrunk with age, you'll be glad
you got them. They're about $16 a set.
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