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Changing Spark Plugs on 91-94 Explorer

larrydd999

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I realize this thread is a bit old, but hopefully someone can help... I've noticed both short and long threads on the plugs sold for the 92 4.0 and would like to know which is right - or are they both ok? Apparently there was some change made, but I've searched and not been able to find out what it is.
 



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Harpua216

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you are correct, there was a design change and there are longer threads on some of the new spark plugs. depending on your year i think most people use Autolites AP605 for 93-94 or AP105 for 92-92. Please dont take my word for this, but i went from the AP765 (which i believe are now the AP605) to the newer design. you can find the 765's with the short threads at some parts stores, but the reason i think they made longer threads was to make sure they arent blowing out of the engine. but please someone correct me if I am wrong.
 






larrydd999

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Thanks for the info. I'd probably be smart to stay with what is now in the engine since it does work, just needs replacement. (Now if I could just figure out a simple way to replace the leaky valve cover gasket on the passenger side...)
 






mr cribb

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I have no idea. I went and picked up motorcraft plugs for my 92 approx 14 months ago, and only checked the gap to the correct specs. I never really considered a short and long thread plug.

I have put approx 20k miles on the motorcraft plugs and wires.... LOVE THEM and HIGHLY recommended. I picked them up from advance auto parts.
 






yragsapo

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I have a '94 and Autolie told me the 605's were right for that vehicle, as I was confused since some sites said the 105 was good for my year while others said the 605. I think your best bet is to call Autolite's customer service. They'd know best.
As for the valve cover gasket. I had that problem on my '94 this year. I had the mechanic change them only to find out that they still leaked because the covers had begun to rot around the holes. He didn't charge me the labor to re-do the job a month later, but I supplied the covers, which only seem to be available from Ford.
BTW... I found that the pair of covers were $45 cheaper than the local dealer when I ordered online from Jim Vreeland Ford Parts. Link
 






larrydd999

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Thanks to all of you for the thoughts and suggestions. I didn't think about the valve covers having a problem, so will be sure to take a look. I do appreciate your mentioning it.
 






Tony H

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whe I first got my 'X' I did ti sbasic tune up.. My plugs looked just like that. The gap was huge, I couldn't believe the thing Started and ran as well as it did.
 






HadAFalcon

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Thanks to this excellent write-up and input from lots of folks, I changed the plugs in my 92 Ex in about an hour. That pesky passenger-side plug nearest the firewall was much easier to replace than I had thought. I jacked up that corner, with the wheels turned far left, and was able to get at the plug with no problem, even with my fat fumble-fingers. Needed just the deep 5/8" socket -- no extension. Now the ol' beast runs like new -- 243K miles and still going, and no oil fouling on any of the plugs. Thanks, everyone.
 






allens1564

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What brand and model spark wire set do you recommend for 94 Explorer? I'd like to use Motorcraft parts.
 






natenkiki2004

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Go double platinum or no platinum at all (copper). The way the spark works is that it fires 2 plugs at once. The spark flows from the coil, through the wire, jumps the gap at the spark plug to ground (engine block) then goes through the block, to the other spark plug on the circuit, jumps backwards, through the wire and back to the coil.

One side of the engine fires from the center electrode to ground while the other fires from the ground to center electrode. Having platinum on one side of the plug won't benefit one side of the engine as far as longevity. You'd have to switch the plugs from one side to the other halfway through their recommended life.
 






MrQ

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Go double platinum or no platinum at all (copper). The way the spark works is that it fires 2 plugs at once. The spark flows from the coil, through the wire, jumps the gap at the spark plug to ground (engine block) then goes through the block, to the other spark plug on the circuit, jumps backwards, through the wire and back to the coil.

One side of the engine fires from the center electrode to ground while the other fires from the ground to center electrode. Having platinum on one side of the plug won't benefit one side of the engine as far as longevity. You'd have to switch the plugs from one side to the other halfway through their recommended life.

What?:scratch:

Nothing goes through the block except the ground, not the spark.

To answer the question ASKED, Motorcraft Double Plat fine tip for a 4.0 SOHC, or Autolite or Motorcraft coppers for the OHV. You can use Motorcraft wires, but the Bosch work just as well. Double check your gaps and NEVER trust that they come pre-gapped.
 






natenkiki2004

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There is no regular "ground", it's a loop. That's why you test the coils together, 3 pairs of 2. The high voltage for the spark goes out 1 wire and comes back in another. 2 plugs are fired at the same time, one on compression and the other on exhaust, then they switch.

Have a look here:
http://rockledge.home.comcast.net/~rockledge/RangerPictureGallery/DIS_EDIS.htm
Quoted from the above article:
Both DIS & EDIS are of a waste spark design. In other words, a single coil fires two seperate cylinders at the same time. The spark plugs in the two cylinders are in series electrically, with the circuit being completed through the cylinder block. When a coil fires, high voltage current flows INTO the top of first plug and OUT the top of the second plug, completing a big loop in each case. This means that the firing voltage of one spark plug is negative with respect to ground, while the other is positive with respect to ground. Half the spark plugs actually see a different polarity than the others do.

This info pertains to what spark plugs to get because if you get single platinum plugs, one side of the engine will eventually have more wear on the plugs because they're being fired backwards and the positive side doesn't have platinum. That's why you need double platinum to get the most life out of them.
 






yragsapo

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What brand and model spark wire set do you recommend for 94 Explorer? I'd like to use Motorcraft parts.

Over the life of my truck, I have tried several different brands of spark plug wires. I have had the best luck with the Bosch 09645 spark plug wire set. It is what I have in my truck now. Excellent quality wires excellent shielding.

One other tip. If you haven't ever changed your ignition coil pack, and are having a rough idle, try replacing the ignition coil with a new one. I purchased the Richporter Technology by Spectra Premium C-507 Coil Pack from Amazon for about $20 (Amazon Warehouse Deals - damaged box). It sells for about $33 new.Link After replacing the plugs (Autolite single platinum) and wires (Bosch), I had found that it was still idling a bit rough and missing occasionally. Changing the coil pack really helped. The engine is smoother than I can remember it being in years.
 






allens1564

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Changing Spark Plugs

Thank you for the advice.

My ignition coil pack has been replaced and has helped quiet the rough idling and missing from before (had to show a mechanic how it was behaving, cuz I didn't know what the hell was wrong with it, before he changed out ignition coil).

But it still misses/jitters a little so I thought hey, the plugs, wires, fuel filter, are a little over 14 months old, distributor cap 3 years old, maybe it's the plugs & wires. (my usual mechanic said my plugs needed to be hot SOLDERED to the wires in order to be secure)

But in one of the explorer forum posts that summer heat can melt it away. I've never read anything about needing soldering for installing plugs/wires.

Think I might need a new mechanic.
 






MrQ

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What? Soldered to the plugs?

Walk away from that mechanic right now.

Also there is no distributor cap if you are talking about the 4.0.
 






natenkiki2004

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The wires I've seen have been a carbon type material inside (I forget the exact name) not actual wire like copper. You cannot solder that at all, it will simply burn the 'wire'. Maybe he's talking about the boot connector part, soldering it onto the wire rather than crimping it on but again, you can't solder modern/performance wires since there is no 'wire'. I've also never seen a plug soldered to a wire, they're always removable. Some wires are part of the coil itself and some don't have wires at all, like modern DOHC's that are individual coils that you stick onto the plugs directly.

I'm not even a mechanic and I know this, I'd be looking for someone else to take work to.
 






TedStryker

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A shout out to the original poster for the nice write-up on replacing the plugs and wires. I just did mine and I'm sure it would have taken me MUCH longer without this valuable info. Thanks!
 






MrQ

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You're welcome.
 






trozei123

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i need to do this on my 92 so bad. i bet it will help get some more life out of the engine and get my mileage up a couple of points.

i know this site is for explorers, but i have a question about my fiance's 2011 ford escape. her gas mileage has gone south quite a bit. she usually got around 21.5-22.0. it only has 84k miles on it. i know the tires definitely need replacing, as they all fail "the penny test" for tread depth. would tires only cause the gas to drop to 19.7? how often should the spark plugs be changed? if changing the plugs will help get the gas mileage back up along with the tires, then i know now what should be done.
 



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yragsapo

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You wouldn't see a 2-3 mpg drop from low tread alone. Low tire pressure, perhaps. As for spark plugs, it depends on the type you're using. Copper plugs should be changed every year or two, depending in how many miles you put on. Platinums last longer. Double-plats and iridium plugs can go 80-100K, if the car doesn't burn oil.
 






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