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Discussion Starter · #1 ·
The 91 and later 1.9 engine has a tendency to arc to the block when the spark wires get a certain age. I have always been able to solve this by putting on a new set of plug wires, but this time no go. I installed a new set of Bosch platinums and Motorcraft factory wires, but I am still getting arcing to block. I even tried deburring the top edge of the spark plug "pocket" and cleaning it with brush and solvent and applying spray paint to insulate, no difference.
 

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???

How do you know that the wires are arcing to the block? If you just put new wires on, there is no reason for the wires to be arcing, and I doubt they could be arcing.

Better describe your problem and you will get the answer you need :wink:

Matt 8)
 

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does it act up with standard plugs and new motorcraft wires? In some aplications platinum plugs need larger gaps compared to standard plugs. My 91 lx got its first set of wires at 100,000 miles with no difference in performance. I installed wires and plugs from the dealer with no problems. I cant explain why new wires wont prevent arcing. I would try installing standard plugs, properly gapped. Check around the engine compartment with an ohm meter and make sure the engine and componets are grounded to the body. Next I'd go to my U-Pull it junk yard an get another coil pack. Make sure those wire ends are seated on the plugs with dielectric grease.
 

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Discussion Starter · #4 ·
I know it is arcing to block because I have logged over 350, 000 miles on two different escorts with same engine and after this happened the first time I found out about the tendency for this to happen to this engine and have had this happen many times since. But this time I even observed the spark jumping by having a helper put the engine under load after dark while I watched. I have since learned that some times the thing that starts the arcing is a combination of old wires and the fact that plugs with too many miles have too great a gap and the resistance of too much gap makes the spark seek out the block because of the proximity of the block to the boot and the fact that the gap being too wide creates a little too much resistance. So with this info I will take out the plugs and cut down the gap a little and see if it helps.
 

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I have never had problems with any of my wires. I changed mine at about 120 000 mi / 9yrs just because they were still original, but they worked fine. I did notice a small improvement, but about a big of a gain as wires will get ya. Before and after I have never had any problems with either OEM's or Neihoff's. I also run Bosch platinums and the gaps stay pretty close to spec over the year I leave them in there. I change my plugs once a year regardless.

If you have arcing occuring your car is gonna run like crap as the spark is going to the block, not your spark plug. What concerns me more is that you may have gotten paint in the spark plug threads and seat effectively insulating the spark plug from the head. At the very minimum, the threads and the seat for the spark plug need to be bare metal for them to work effectively. If you "insulated" the plug from the head, the current has no place to go, so it will start arcing from the wires to the closest ground it can.

Also, what's your gap set to?

Matt 8)
 

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Discussion Starter · #6 ·
Latest update: tried one suggestion to install Motorcraft plugs and gap slightly under spec and use dialectric grease, this was done today and still no difference. So, bottom line is I have replicated all ideal conditions as far as plugs and wires are concerned. I must have a "red herring" situation where the cause is not related to what normally causes these conditions to exist. I will have to bite the bullet and take it to the shop and let them put it on the analyzer unless I get a rational suggestion on what else I can try.
 

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Funny thing, my son's '91 was missing badly. Found the #3 arcing down the side of the plug to ground. It had made a real carbon track so replaced the plug. It soon repeated with the new plug, so I closed the gap a good bit, and that cured it. Although these modern high voltage systems easily jump .060" gap, they will work just fine with .030" like used to be common.

Curiously, at the same time I traced an idle knock to a real flat spot on the cam follower on the exhaust valve of the same cylinder. Was pleased to find a new lifter at the local auto parts store, so maybe it's a common failure.

Just maybe the funny cam follower caused something to go awry, making the spark jump on the outside of the plug. Overheating of the plug is all that comes to mind.
GB
 

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Discussion Starter · #8 ·
took out Bosch plugs and installed Motorcraft plugs and cut gap down to
.030 with no change. Any more thoughts?
 

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If you have acess to a u-pull it yard where you can get a coil pack for $10, I'd try that. Otherwise a machine with a scope might be your next step. Coil pack, plugs,wires or a bad ground? I went to my u-pull it yard this weekend only to find it closed."snow"
 

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Discussion Starter · #10 ·
I have taken car to two different dealers since last posting. First dealer was clueless. Took to old reliable dealer and they replaced ox and maf sensors and claimed it was fixed. I went to pick it up and it was no different. The idiots just drove it around the block like I told them wouldn't work. I took idiots on test drive and made it misfire and they were mystified. So I left it with them and they still can't figure it out after several more days of tests. Any more suggestions?
 
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