History: 1997 Explorer, 5.0 L V-8, 68K miles, nothing major ever replaced, routine maintenance as per recommendations in service guide.

Problem: Engine skips when revved from idle (in park). Also skips and surges at all road speeds, though most pronounced between 45 and 60 miles per hour or under a load (gradual uphill grade). No CEL display or codes though. Next day, same thing. CEL illuminated this time, so I scanned and got a P0300 code (random misfire). Replaced all 8 plugs (Motorcraft double platinum OEM plugs gapped at .053") and replaced fuel filter. Problem persists. Checked the coil packs, and the resistance measurements were within spec. (primary 0.5 ohms, secondary 14.86 K ohms). Checked each plug wire and the resistance readings ranged from about 8K to 14K ohms - well within spec). No smoking gun yet. Bought a new set of wires from the dealer and installed them anyway. Road tested again. This time the CEL started flashing and I noticed a foul exhaust smell (you know the bad catalytic convertor smell). Scanned and got a P0308 code (cylinder 8 misfire). Runs like it is severely wounded.
Ignition system is OK I think. I plan to check the fuel pressure and pressure regulator next. What else should I test? Any help greatly appreciated.

Don

 

I had a similar problem with my 98 5.0. I went through the same steps, replacing plugs, etc. Finally bought new wires and that cured the problem.

Because you changed the symptoms slightly when you changed the wires, I suggest you recheck each one of them for good connection. Sometimes the plug ends will stay on the plug but not be completely snapped on the plug.

Also check to see if you may have dislodged something during the install.

When I was troubleshooting mine, I learned that the coils fire in banks, so I even tried switching cylinders (be sure to read the documentation) to eliminate the coils as culprits.

Good Luck!


Winford

 

I finally solved my skip. I had a bad (though new)plug in cylinder #8. The connection between the metal base of the plug and the porcelin insulator were loose. You could twist the insulator and feel it move slightly...this was causing an intermittent and sometimes continuous misfire. The plugs were AWSF32EE Motorcrafts. First time I've gotten a bad Motorcraft plug.
I must have needed the plug wire set also, since I had a misfire before replacing the plugs.

A simple fix after all, but a problem with two variables and the same symptoms makes you suspect and chase all sorts of underhood components...

 

Good work! Not too many of us would be willing to check a new component to see if it is defective. Glad you got it resolved!

Winford