Spark Plug Tech

Many Ford engines come from the factory with different platinum spark plugs on the left and right sides of the engine.   On a 2000 3.8L V6 you will find platinum plugs marked AWSF-42E on the LH side (cylinders 1,2,3) and AWSF-42EG on the RH side (cylinders 4,5,6). They appear to have different electrodes. Why is this?

Ford does it to take advantage of the "waste spark ignition system" on our cars, in which there is one coil for each pair of spark plugs.   One half of the plugs see a different polarity from the other half.

Ford Engine	Cylinders	Firing Order
1.9L	4	1 3 4 2
2.3L	4	1 3 4 2
3.8L	6	1 4 2 5 3 6
4.6L	8	1 3 7 2 6 5 4 8
4.6L 32 Valve	8	1 3 7 2 6 5 4 8

The chart above illiustrates the firing orders and polarities for Ford waste spark ignition systems. The red numbers are positive firing spark plugs. The blue numbers are negative firing spark plugs.

These differing polarities cause the spark plug electrode metal (platinum) to erode differently, depending on the direction of the current flow of the spark. On one side of the engine metal is transferred from the tip to the electrode. On the other side it goes from electrode to tip. This allows Ford to save a tiny bit of platinum on each plug installed at the factory by using plugs with only a platinum tip on one side and plugs with only a platinum electrode on the other.   Doing this may only save a few cents per plug, but it adds up. Just think how many spark plugs Ford installs.

The replacement platinum plugs specified for our cars (AWSF-42EE) have platinum both on the tip and the electrode, so they can be used on either side. Another replacement option (the one I chose) is to install copper plugs in the same heat range (AWSF-42C). I install new copper plugs every 15,000 miles.

Tools for Spark Plug Installation

Any job is made easier if you have the right tools. I've found that this is what I need to change the spark plugs on my 2000 3.8L V6 Mustang.

• You may have to shop around to find a gapping tool with feelers that go up to 0.054".
• The rubber hose slips onto the spark plug electrode to hold the plug while threading it into the block. Works great. Try it.
• Smear dielectric grease on the spark plug electrodes and tips to make them waterproof and prevent arcing. Also makes the boots easy to remove/install.
• The anti-seize goes on the spark plug threads to keep the plugs from seizing in the aluminum block. You'll be glad you used it, next time you change the plugs.
• I use a boot removal tool to avoid damage to the plug wires. Pull on the boot, not the spark plug wire!.