A. Verify it's a short crank.
The short crank engine uses a four slot pulley. Count the slots
in your pully. If
it has eight slots, it is not a short crank engine. While all engines
can fail if the
crank bolt gets loose, the short crankers are more likely to fail.
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B. Is it really slow?.
Drive another miata and compare. If your car feels much slower,
there could be an issue.
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C. Does the pulley wobble?
It's pretty subjective, but when the bolt is really loose, the pulley
will seem to wobble. Compare it to another pulley, such as the water
pump, power steering, or AC pulley.
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D. TDC Check
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When the piston is at top dead center (TDC), it will be at
the top of its stroke. If thekeyway is not damaged, the timing
mark on the crankshaft pulley will line up with the timing
scale next to it.
If one removes all the spark plugs, the engine can be rotated
to TDC by putting a long rod down the first spark plug hole
and "feeling" when TDC is reached.
You will need a 21mm socket on the crank bolt and a suitable
wrench. Only rotate clockwise.The Mazda Shop Manual says never
rotate counterclockwise.
You may have to remove the intake tubing to get room to turn
a wrench here.
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Here's what I saw on my car. The #1 piston is at TDC. The
timing mark is about
16 degrees before that. It corresponded to the wear in the
crankshaft keyway when I took it apart..
Too bad, no?
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F. Remove Bolt and look
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I've never done it, but have read it's also possible just
to remove only the bolt. Then with a mirror, or digital camera,
do a visual inspection. A good one looks like this.
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