Slow loss of power and MPG, no CEL's or drivability issues

[2000StreetRod]

waste spark ignition

The second generation Explorer's have a waste spark ignition system. Two plugs fire at the same time - one of the compression stroke and one on the exhaust stroke. Waste spark ignition systems are less expensive to manufacture. Ford claims their system reduces pollution by firing on the exhaust stroke but I doubt that the mixture is even combustable.

Because one section of the ignition coil fires two plugs (one of each bank) the current flow thru the plugs on Bank 1 is opposite to that on Bank 2. The direction of current flow impacts wear on the plug. Each time the plug fires a small amount of metal is removed from one electrode and deposited on the other electrode. The factory plugs in Bank 1 used to be different than the plugs in Bank 2 and had different part numbers. I purchase either double copper or double platinum electrode spark plugs for my Sport. That way it doesn't matter which bank they are installed in.

 

[Cranmaro99]

The second generation Explorer's have a waste spark ignition system. Two plugs fire at the same time - one of the compression stroke and one on the exhaust stroke. Waste spark ignition systems are less expensive to manufacture. Ford claims their system reduces pollution by firing on the exhaust stroke but I doubt that the mixture is even combustable.

Because one section of the ignition coil fires two plugs (one of each bank) the current flow thru the plugs on Bank 1 is opposite to that on Bank 2. The direction of current flow impacts wear on the plug. Each time the plug fires a small amount of metal is removed from one electrode and deposited on the other electrode. The factory plugs in Bank 1 used to be different than the plugs in Bank 2 and had different part numbers. I purchase either double copper or double platinum electrode spark plugs for my Sport. That way it doesn't matter which bank they are installed in.

Yeah I just read that the 2nd Gen's use this type of ignition system, and now it makes sense that the OPs car runs much better after replacing the plugs and wires.

But long story short, it's OK to just get stock replacements as long as the correct wires are used on the correct plugs?

 

[joecrna]

The data is finally in. It supports my seat of the pants impressions. Can I once again say WOW!!! Most of the improvement came with one change, plugs and wires. I commutted in the Explorer over another week and accumulated almost another 1000 miles. After looking at my data in graph form, I noticed that what I had previously considered statistically insignificant or below the resolution of my testing methodology appears to be a trend.

I now divide my results into three sets; baseline, low point (just before maintenance and changes to find my lost power) and now (after the plug and wire change). MPG has rebounded. Baseline 17.8, low 15.5 (down 13% from baseline) and now 16.8 ( only down 6% from baseline). Performance is coming back too. 0- 60 Baseline, low ( baseline + 32%) and now ( baseline + 14%). 1/4 miles baseline, low( baseline + 26%) and now ( baseline + 13%). 0-60 improvede by 3.5 seconds and 1/4 mile by 2.5 seconds with just a plug and wire change.

Remember this vehicle had no CEL's or drivability issues.

Maintenance to date includes; rear axles seals replaced, rear diff fluid changed, fuel filter, checked compression, checked collant temp sensor, air filter, oil change, oil filter, transfer case fluid change, front diff fluid change, transmission fluid flush and plugs/ wires.

Still to come; MAF sensor cleaning, O2 sensor replacement.

Any further ideas?