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Ford Ranger and Misfires

My 0998 Ranger has had progressive symptoms of misfiring over the past couple of months (beginning in around May). I was living in Northern Illinois then, and the first symptom was that after a rain (or during, I suppose) upon startup the car would shake somewhat violently when idled, and beginning to move the car would fix that shake.

In August I moved to Atlanta, and the truck made the trip just fine, suffering only on the mountains in Tennessee, as one would expect. Once in Atlanta, the problems magnified - it began shaking upon startup all the time, but only in idle, and felt like it was losing power (slow acceleration) more often. The check engine light came on in Tennessee when I was visiting my fiance’s mother at the end of August.

Ignoring that, sometime in the middle of September I got a new symptom, one morning I was driving out of my apartment complex (requires you to wait at a gate while going up hill) and it started clicking while running, and generally not delivering much power at all. It was able to make it slowly up the hill, and then the rest of the drive was just shaking at idle as normal, the clicking and severe power loss was not there. I took it to a nationwide service chain, and they charged me $100 to do an ODB-II read (even though when I asked they said they would perform real diagnostics). Turns out two of the cylinders had misfired, though I don’t remember which two. They suggested replacing the spark plugs, wires, and coils and wanted $500 to do it, but said that they didn’t know if that would fix it or if I would have to go on to replace the fuel injectors (or more).

Strangely, the afternoon of the day the clicking and power loss began, the car ran perfectly. Perfect acceleration, proper idling, everything. I’ve found that if I drive a lap or two around the apartment parking lot the car does not click or have severe power loss when climbing that hill.

What do the board experts think? Sparks, wires, coil packs (i’ve researched a bit and get the impression this national chain wasn’t entirely certain about the electrical operation of this truck)? Fuel Injectors?

Maintenance History: It’s at about 130,000 miles right now and we probably put on half of that (bought used). Don’t know about the maintenance history before us, but we have not changed anything but the oil since we got it.

If changing the plugs is a good idea to fix this, where can I get a decent layman resource for changing plugs? I’ve never done such a thing and would need to know what tools and tool sizes to expect to need, and if this would be economically feasible to do myself ($500 to change the sparks and wires seems like an awful lot, but I can’t speak to the coil packs).

Also: I rarely drive on the highway in Atlanta (take 30-40 mph surface streets) and the truck can have trouble maintaining 40 mph going up a hill. A recent drive on the highway revealed difficulty getting past 65, 70 being about the max I could push it, used to be the max was a little over 80.

I’m leaning toward bad spark plug wires, since the problems began after it rained. I also think it’s time for some basic maintenance. Changing the oil isn’t good enough. While you’re changing the wires, change the spark plugs, air filter, and fuel filter. I’d suggest you pick up a Haynes manual (my favorite) or Chilton’s manual. They’ll have step-by-step instructions for your vehicle.

While I wait to get a Haynes manual, I was looking at parts. I see I can get plugs from $3-4 each, a wire set for around $40. Do those seem reasonable, or too cheap? What i’m seeing is that the ranger has one “coil pack” instead of a coil per plug, is that right? Essentially i’m replacing all the coils at once (not that they don’t all need to be replaced anyways)? I’m reasonably certain the air filter is new, and who makes a good fuel filter? For that matter, who makes a good replacement coil pack?

Replace the spark plugs and wires first, they are long overdue, if that doesn’t fix it then you can replace the coil pack. I can’t believe you put up with this problem for so long and drove it so far without doing anything about it. Of course with the miles you have put on with no maintenance you could have a whole host of problems.