What can cause an arc through the plug wires and the coil wire causing the engen to misfire?

Tiny
SPEHL
  • MEMBER
  • 1993 MAZDA PROTEGE
  • 235,000 MILES
I have a 1993 Mazda Protege. The problem I am having is a misfire through the distributor. I can hear and see the electric arc and yes, I have felt it too. It has juice. I have replaced the distributor, the coil, the coil wire, the igniter and the resister, nothing helped. I have also looked at the ground wires and see nothing odd, but I have only looked at the battery ground and the one on the side of the head. What am I missing? I can feel the engine******** when I'm driving.
Thursday, December 29th, 2011 AT 2:07 AM

3 Replies

Tiny
CARADIODOC
  • MECHANIC
  • 34,078 POSTS
The parts you replaced are involved in producing the spark. You have spark so why would you replace those parts? If the engine is running, you know spark is getting to the spark plugs, at least most of the time. If that spark is occurring at a different location, there is either a carbon track or some other reason the spark is not jumping the spark plug gap. The spark is always going to occur at the point of least resistance. A carbon track is a perfect example. Most of the time that can not be cleaned sufficiently to prevent the problem from coming back.

While a carbon track makes it easier for the spark to occur at the wrong place, the same thing can happen when it's harder to jump at the right place. Look for a carbon-impregnated string in the spark plug burned away from the terminal. That is the single biggest reason for a misfire, and new wires will take care of that. That makes it hard for the spark to get to the plug so it looks for an easier way to get back to ground.
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Thursday, December 29th, 2011 AT 2:19 AM
Tiny
SPEHL
  • MEMBER
  • 2 POSTS
Thank you for your help, I found the problem. It was a bad crimp on a plug wire on the spark plug end. I changed it and the arcing stopped. In reply to the question as to why I replaced the parts that I did; my car has 235,000 miles on it and increasing daily, the o-rings in the distributor were leaking oil to the inside, and it was the original equipment, so I thought that was part of the problem, I changed the igniter and resistor because I thought the dwell may have been incorrect or the voltage to the coil was to much. I do not have any testing equipment, so I'm going off what I know. I changed the coil because the one that was on the car had started loosing its isulation, so naturaly I thought it was grouning out some were inside. The coil was the first thing I changed then the distributor then then the igniter and resistor. Finaly last and most simple were the plug wires. But again, your information was very helpful, and it did lead me to a solution. Thank you.
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Friday, December 30th, 2011 AT 1:51 AM
Tiny
CARADIODOC
  • MECHANIC
  • 34,078 POSTS
Happy to hear you had a legitimate reason. Too many people randomly throw parts at a problem thinking one is going to stick and magically fix the problem. That is a very costly and ineffective troubleshooting method.

Happy too that it's solved.
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Friday, December 30th, 2011 AT 2:34 AM

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