Miata Mailing List: July 1993, Message #71
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   From: Andy Poling 
Subject: Re: IGNITION WIRES
   Date: Fri, 9 Jul 1993 11:23:19 -0400


On Fri, 9 Jul 1993, John W. Driver wrote:
> I was talking to my dealer's service writer today (ouch - new battery
> after 3 1/2 years), and he has an interesting theory about the skipping
> (missing) that happens around 30,000 to 35,000 miles, and results in
> the replacement of spark plug wires.  He thinks that the spark plugs
> are worn out at that mileage and the resultant higher resistance, and
> thus higher voltage required to fire, them "blows out" the ignition
> wires, which causes the wires to start shorting out.  Any of you
> electronic geniuses have any thoughts on this?

Yeah.  I think his theory is about as sound as the one that says that your
car knows when you have extra money to spend (so something can afford to
break).  :-)

It is far more likley that the high underhood temperatures that modern
autos endure eventually causes hardening and subsequent cracking of the
insulation on the spark plug leads.

-Andy

Andy Poling                              Internet: andy@jhunix.hcf.jhu.edu
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