New Motorcraft SP-500 Plugs cleared my code, Explorer Sold at 280K miles
I fixed my '98 Explorer Sport by replacing previously installed Autolite 103 plugs (purchased from AutoZone) with Motorcraft platinum SP-500 AGSF22FM plugs. I replaced the wires with Motorcraft wires at the same time. The wires were only about two years old and the plugs were installed only 4 months ago. Thanks to this forum for one author's detailed write up on how to remove passenger firewall side Plug #3 which I was able to reach by turning the wheel all the way left, removing the mud guard from the passenger front wheel well, using a standard 5/8" deep socket (not a 5/8" spark plug removal socket), using a u-joint adaptor on my socket wrench, and crawling underneath the passenger side behind the wheel while reaching my arms up through from underneath to feel for the plug. Do this with a COOL Engine only.
The spark tip of the Motorcraft plug is round whereas the spark tip of the Autolite 103 plug is flat. I don't have scientific evidence to support this, but I wonder whether the Round tipped plug from Motorcraft produce a more reliable spark than the Flat tipped plug from Autolite? My anecdotal evidence is that she runs better than you can imagine ... INCREDIBLY well for a vehicle with 280K miles!
I sold my '98 Explorer with 280K miles with an engine that was running more smoothly than ever. I would like to thank Ford for building such a reliable machine. Now I find myself missing Big Red something aweful.
Happy Motoring ...