Misfire... New wires arcing?


#1

Hey guys,



I’ve got a 1996 Ford Probe GT with the Mazda/Ford 2.5 liter V6. I’ll spare you the long story and tell you all exactly where I am at right now, but I would be more than happy to clarify and answer questions.



The engine misses/misfires/stutters when… Well, when its on. Originally it was very rare, but now it happens every 20 seconds or so at best. It happens when idling, it happens when accelerating, and it happens while cruising.



I replaced the spark plugs as well as the spark plug wires. It had no effect. The problem is still getting worse. It has gotten so bad, the car has shut off on numerous occasions.



Multiple mechanics at a trusted shop near me isn’t are not sure where to go next. There is very noticable arcing happening. It is happening between the wires and the block. It can be heard elsewhere, but not spotted.



There are no codes being set, the new plugs (NGK’s) were replaced with another set for testing, and yet another new set of plugs were tried. The arcing continues. The cap and rotor was inspected, but not replaced.



The distributor is a common problem on this engine and this was was replaced about 10,000 miles ago. I have the records of this as it was done before I purchased the car. I have no contacted the facility. Is there any chance there is a warrenty on this distributor that they might have a record of?



The mechanics I was with today recommend I take the car to the Ford dealer for diagnosis. Due to the inconvenience and the extremely high costs, which are hard to justify right now, I ask this board for advice.



Does this all lead to a bad coil, which in-turn means a new distributor? Is anything obvious being overlooked?



Any and all comments or suggestions would be greatly appreciated.



Thanks,

Brian


Spark Plug Wire Arcing at Spark Plug Wire Boot and Ignition Coil Connection
#2

Get the engine trouble codes. Bring them here for advice, We need those codes. You can get an auto parts store to scan the “check engine light” for free. It makes troubleshooting the problem less difficult to have the codes. That’s their reason for being after all.


#3

Thank you for the reply.

As I stated in my initial post, there are no codes being set. The diagnostic software that the mechanic had does not pick up anything, nor does the cheap equipment at the local auto parts stores. There is no check engine light and no codes being picked up. Even when the car died, it didn’t trigger one. That is making this problem all the more interesting…

One of the reasons I am being pushed towards the dealer is that my mechanic thinks their equipment might be able to get more imformation out of the cars fairly immature OBD II system. So, no help from the car here…


#4

If there is arcing, the wrapping around the wires is breaking down under the voltage. It should not arc.
If you have seen arcing, return the wires. Buy some different ones. I am not sure what good brands are now, but I do know that there are many cheap inferior ones on the market, even some sold by the manufacturer companies.


#5

When arcing like this occurs it is most likely due to a bad ground connection between the coil and the plugs. If the arc can’t find a good ground path through the plug gap it will find it elsewhere at the next weakest point.


#6

If the arcing is constant and lightly heard, it may just be the fuel injectors working; you can hear them. Has anybody touched the wires to get a shock? That would prove the arcing at least. I hope you didn’t try to get by with a 12 dollar wire set. Did you get the distributor rotation right or the cylinder numbers right. Hope so. They may have you in their computer and have a record of the warranty.


#7

The arcing is visible between the wires and the block.

The replacement set of wires is NGK, which have a great reputation for being the best plug for this engine.

The first thing the mechanics did after finding the arcing was to put electrical tape around the wires where the arcing was occuring, which was where the rubber goes into the plastic housing that goes over the spark plug. This didn’t work. A new set of wires was installed (for some reason the mechanic just had to make sure) and it actually made things worse in comparison to the NGK wires.

Cougar, I understand what you’re saying, but I don’t understand the solution.


#8

Cougar’s solution probably involves checking/cleaning all the ground wires in your ignition system.

Are you running MSD or something like that?


#9

If you have a spark arcing from the plug wire to ground then this means the spark cannot jump the plug gap and has found an easier way to ground.
This normally means a defective spark plug or there is something going on inside that cylinder(s) (low compression, too rich, coolant, etc.) to kill the plug(s) while it’s under compression.

It’s also possible that a weak coil is the problem. The coil may be struggling to put out enough voltage to jump the plug gap which is under compression in the cylinder and the coil decides that a lower voltage spark has an easier route to ground - through the plug wire boot.

The use of an oscilloscope would probably show this problem but you would be looking at a diagnostic charge for taking a look at what is going on in there. I won’t go into an explanation of how the coil works. A net search should produce that and should explain dwell, field collapses, build-up time, etc.


#10

I guess the question is, is this sometthing I can solve myself?

The coil is my uneducated-inclination at this point as well as a possibility given by my mechanic. It appears that this is an integral part of the distributor… Are there ways of testing it with equipment available to me?

Also, this problem has been getting progressively worse. Since the first time it occured randomly on the highway, to it being a pretty dependable misfire, to the car shutting off, does that sounds like the symptoms of a coil killing itself off?

The spark plugs were the first thing I replaced when this problem appeared. Then the replacements were replaced yet again, so I think they can be ruled out as the case. This might be a stupid question, but would there be anything gained from significantly decreasing the spark plug gap to see if the problem goes away? Could this do anything as far as confirming the coil/distributor as the problem?

Thanks guys!!!


#11

Just curious. Have any codes been pulled yet? AutoZone will do this free and there could be something lurking in there.

The symptoms you have can be indicative of a failing coil and the idea of closing the plug gaps up is not really stupid. For each .001 the gap is closed it drops the voltage the coil is required to put out by about a 1000KV. (Memory here, it’s been a long time.) However, do not leave them like this as they will have a tendency to foul easier. If you do this, try about .025 and see what happens.

The only static test you can do on the ignition coil is performing a few resistance checks with a VOM. This may or may not give you the whole story as heat is often what causes the problem and the heat can vary of course.

This is the coil I’m referring to. The one in the distributor is probably not the culprit.
http://www.partsamerica.com/ProductDetail.aspx?MfrCode=MOT&MfrPartNumber=DG470&PartType=190&PTSet=A
Note it’s a ho-hum old Ford coil and with a little scrounging you may be able to dig one up for a little or nothing.
On the pic of the part note the “See all vehicles this part fits” notation. Click on that and it will give you a long laundry list of vehicles a part could be pirated from.

Hope some of that helps anyway.


#12

How can you tell the spark plug wires are arcing between the wires and the engine block? Can you see, or hear, the sparks?
To best see any sparks, run the engine in a dark place and watch the spark plug wires and the ignition coil .
Spark plug wires which are too close together can INDUCE spark in each other. Are yours bound together? Do they run, parallel, nearly touching? Quality spark plugs wires shouldn’t arc to ground. Did some one pierce them with a test probe?
To ensure there isn’t a ground problem between the engine block and the car body to battery negative, clamp a wire to the engine block and the negative post of the battery.
There should be trouble codes coming from the engine computer. When you turn the ignition key on, does the check engine light come on for a few seconds and then go off? If it doesn’t, there is something wrong with the engine computer wiring, or the engine computer. Has a CD player, radio, etc, been added to the dash? If so, did the installer know exactly the correct wires to connect to under the dash, or, was “just any” hot wire used for power? If it was, that could be your problem with getting trouble codes from the engine computer.


#13

I would suggest going to the dealer and getting a set of wires from them. While NGK has a good reputation and I would choose them over most plugs, there is just something about OEM that seems to work. The same goes for plugs, I suggest getting Ford brand (Motorcraft?)

I have not seen any comments about possible modifications to the ignition system. Has anyone done some sort of performance modifications?


#14

Find yourself another “mechanic”. Mechanics don’t wrap electrical tape around plug wires to stop arcing


#15

Thanks everyone for the replies, let me try and answer some of your questions (even though they were all answered in the origiinal post).

No codes have been pulled, the check engine light is not on, the check engine light DOES work, multiple OBD II readers have come up with nothing.

There have been no modifications of any kind to the electrical, mechanical, or any other aspect of this car. Everything is completely stock.

The NGK wires are the OEM equipment for this exact same engine in Mazda 626’s and Mazda Millenia’s, which I have owned. Within Mazda and Probe owners, these are regarded as the best option. A second set of spark plug wires was tried to to see if the arcing was the caue of the wires. The wires tried were Motorcraft. The NGK plugs are the same story.


#16

Whatever kind of high voltage coil your vehicle uses, there is a connection to the engine block ground. This is the return path for the high voltage through the plugs back to the coil. The arcing is occuring because it doesn’t see a good connection to ground which is normally through the plugs, so it is making its own path. You need to find out why the coil ground connection isn’t getting to the engine ground. The old conventional coils tie the ground internally to the metal case of the coil and connection to the block is made through the coil bracket. You also may now have to replace any of the components that the arcs are going through since they may now be damaged. The arcing will make a conductive path as the arc burns through them.


#17

The bottom line is that if the spark is arcing from the plug wire to ground it is caused by the inability of the spark to jump the plug gap.


#18

Yes, but to be more clear, that isn’t due to a fault in the wires or the plugs. It is the coil grounding that is the problem.


#19

Thank you guys! Cougar and ok4450, you’ve helped me a great deal in understanding exactly what might be going on here. I appreciate your time.

The question now is, is there anything I can go do in my garage to rememedy this problem, or am I going to have the seek the help of the Ford dealer or some other mechanic that might be able to troubleshoot this thing? Am I most likely looking at a new distributor hear?


#20

You need to see how the ground for the high voltage COIL is made and check it. You may be able to use an ohmmeter to check the continuity between the secondary coil and ground. I am not familiar with your system so I don’t know what kind of setup you have. I will try to do some reasearch. Replacing whatever kind of coil you have may fix things. But like I stated before you may now have other things damaged due to the arcing. You first need to solve the main problem though.

You are welcome for the help.

EDIT:
I looked at a drawing for your car and it just showed a basic block for the distributor. It showed a couple of wires going to ground which are black and the other is blk/red. These should be tied to ground. I don’t know if they are for the high voltage ground though. There may be something else for it.