Why different plugs on bank1 vs bank2?

[Elliott hopson]

Just changed my plugs over today to motor craft sp500 on all 6 cyclinders. I noticed the plugs on 1 side were different then bank 2 side. Also noticed bank 2 side had blue paint marker on the ends of the plugs. Am I ok to put 6 Identical sp500 plugs in? These were original plugs at 101xxx miles and were almost all completely siezed! Gap was .090" on bank 1 side and around .070" on bank 2 side. What was fords reason behind this? Thanks

 

[swshawaii]

Spark Plugs for 4.0 SOHC | Ford Explorer and Ford Ranger Forums - Serious Explorations

 

[odinjunior]

No kidding? My '02 still has the original plugs in it at 73K miles. When I change them at 100K I'll look for that.

 

[Elliott hopson]

No kidding? My '02 still has the original plugs in it at 73K miles. When I change them at 100K I'll look for that.

Yes sir, I would recommend you change yours asap, just because since these plugs are platinum, the threads like to rust in the aluminum heads, i had complete hell removing mine and felt like the plug was going to break off on everyone! Even on the last couple threads of each plug it started making an awful screeching sound, almost like trying to gall up. Now I see why people preach to put anti sieze on the new plugs. Scary stuff!

 

[swshawaii]

All of mine came out screechy at only 46k. I mean finger nails on a chalkboard x10 loud. Horrible sound. If the new plugs have a silver finish they are plated and anti seize is not necessary but still recommended by most here. Don't over tighten because anti seize acts as a lubricant. Do NOT use regular anti seize. Use copper or nickel anti seize designed for high heat. Small $1.50 pocket packs are available at parts store counters and is more than enough to lightly coat all the spark plug threads. Same applies to brake caliper pins and hardware. Regular anti seize will gum up and bind over time. Use only high temp silicone lube designed specifically for brakes.
https://www.ngksparkplugs.com/about-ngk/spark-plug-101/5-things-you-should-know-about-spark-plugs

Note the center electrode gaps on the drivers side plugs due to the "wasted spark" system.
Right pic is a "gummy" caliper pin that caused a caliper sticking requiring a complete overhaul.

 

[Elliott hopson]

All of mine came out screechy at only 46k. I mean finger nails on a chalkboard x10 loud. Horrible sound. If the new plugs have a silver finish they are plated and anti seize is not necessary but still recommended by most here. Don't over tighten because anti seize acts as a lubricant. Do NOT use regular anti seize. Use copper or nickel anti seize designed for high heat. Small $1.50 pocket packs are available at parts store counters and is more than enough to lightly coat all the spark plug threads. Same applies to brake caliper pins and hardware. Regular anti seize will gum up and bind over time. Use only high temp silicone lube designed specifically for brakes.
https://www.ngksparkplugs.com/about-ngk/spark-plug-101/5-things-you-should-know-about-spark-plugs

Note the center electrode gaps on the drivers side plugs due to the "wasted spark" system.
Right pic is a "gummy" caliper pin that caused a caliper sticking requiring a complete overhaul.

Was that caliper pin on your explorer? Something funny has been going on with mine, when they get hot they get squishy and the pedal makes noise when I push on it. But lately I been noticing every now and then, when I let off the brake pedal, the truck kind of lunges for a split second. I almost think it feels like a caliper pin unsticking. Not sure if this was a problem or not on the explorer?

 

[TechGuru]

Just changed my plugs over today to motor craft sp500 on all 6 cyclinders. I noticed the plugs on 1 side were different then bank 2 side. Also noticed bank 2 side had blue paint marker on the ends of the plugs. Am I ok to put 6 Identical sp500 plugs in? These were original plugs at 101xxx miles and were almost all completely siezed! Gap was .090" on bank 1 side and around .070" on bank 2 side. What was fords reason behind this? Thanks

SP500 on both sides is the correct replacement, Ford no longer offers the different plugs for each side.

The reason they originally did is because of the wasted spark ignition system.

The wasted spark system is an ignition system used in some four-stroke cycle internal combustion engines. In a wasted spark system, the spark plugs fire in pairs, with one plug in a cylinder on its compression stroke and the other plug in a cylinder on its exhaust stroke. The extra spark during the exhaust stroke has no effect and is thus "wasted". This design halves the number of components necessary in a typical ignition system, while the extra spark, against much reduced dielectric resistance, barely impacts the lifespan of modern ignition components. In a typical engine, it requires only about 2–3 kV to fire the cylinder on its exhaust stroke. The remaining coil energy is available to fire the spark plug in the cylinder on its compression stroke (typically about 8 to 12 kV).

https://en.wikipedia.org/wiki/Wasted_spark

One side the spark is jumping from the electrode to the ground prong and the other side the spark is jumping from the ground prong to the center electrode.

Unlike conventional ignition systems, waste spark DIS ignition systems use half the spark to fire the opposite spark plug unconventionally from the side electrode to the center electrode. Copper core standard plugs and copper core single platinum spark plugs are not designed to withstand this reverse polarity firing and will suffer premature gap growth due to center electrode erosion. Gap growth will stress ignition system components by requiring more voltage to fire, eventually leading to misfire, loss of performance and fuel economy. This degradation can be noticeable as soon as 20,000 miles after the plug is installed. NOTE: Ignition misfire can cause the Check Engine light to come on
...
That is why installing a premium spark plug with platinum on both electrodes or an iridium electrode is recommended for waste spark DIS engine applications. Double Platinum plugs and iridium plugs are specifically designed for engines with DIS systems and are 30 percent more durable than the average spark plug. The platinum-to-platinum firing offers virtually no gap erosion and performance that lasts for up to 100,000 miles.

http://www.aa1car.com/library/sparkplugs_for_dis.htm

 

[Number4]

Show me a 100k mile plug that comes out still gapped correctly. I'd recommend replacing at 70k max, based on my experience.

Don't use anti-seize. As @swshawaii mentioned, the replacement plugs will be silver in color, that is antisieze. While over torquing the 4.0 may not be as critical as the 4.6, you will over-torque which could strip the threads. And don't guess on torque, this isn't the 1980's, let's use torque wrenches people.