Miata Mailing List: June 1992, Message #51
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   From: (none)
Subject: Re: engine missing
   Date: (none)

>    I have a 90 miata, and the engine started to miss about two weeks ago.

There are several things you can check for this sort of problem:
   fuel--
	is the fuel filter or a fuel line blocked?
	is a fuel injector blocked?
   air--
	is the air cleaner obstructed?
	is the exhaust system blocked?  (banana in the tailpipe?)
   spark--
	is a spark plug lead shorting to ground?
	is the electronic distributor misfiring?

However, you mentioned that replacing the plugs improved things for a while,
which makes me wonder if they're fouled again now.  Plugs can become fouled
in a few ways too:
   junk-- impurities in the fuel
	did you use cheap gasoline that might have gunk in it?
	did you use some gasoline additive, like "octane boost" or "dry gas"?
   oil-- oil getting onto plugs
	is your engine leaking oil into the cylinders?  (do you see
		blue smoke in your exhaust?)
   carbon-- incomplete combustion
	as above (spark leads, air/fuel filters, etc.)

Did your dealer say how the plugs were fouled?

My last car, a delightfully irreverent Fiat Spider 1800, developed a similar
problem.  I experimented and replaced lots of parts (fuel lines & filter,
air filter, fuel pump, distributor cap, spark leads, etc.).  As I expected,
the last part I thought of replacing was the one that actually caused the
problem, and was also the least expensive ($3).  It was, or actually they
were -- the 1800 has TWO of these -- the centrifugal distributor points.
Replacing them made the problem disappear, for a while.  Eventually I just
stocked up on them and replaced them whenever I started noticing symptoms.
Not too long after that I bought my Miata and sold the Fiat.  Fortunately
the Miata has an electronic distributor so you can't be having the same
problem, so I guess the moral of the story is to replace the inexpensive
parts first, and start with the spark portion of the equation for this
particular problem.
--
Michael J. Abbott		mja@kpc.com
Kubota Pacific Computer Inc.	Santa Clara, CA		408-987-3303