1. Dunno if I'd call it common, but it happens often enough that there's
a page about it in he miata.net Garage section.

2. About right for a total engine rebuild, not just a crank repair.

3. Probably, if not a low-milage junkyard engine. Read the miata.net
article first.

I'm having a hard time understanding how the crankshaft gremlin could be
causing a protracted lack of power.  I suppose if the crankshaft broke, the
lower timing belt pulley could get loose, and then the rig wouldn't run
right.....for about a half a mile, and then the belt would break or come
off.  But by the time that happened you'd have long lost all your fan belts
and the crankshaft pulleys would be laying in the bottom of the engine
compartment with the stub of the crankshaft still bolted on.

Of course, there might be something about it that I'm not understanding.
Regardless, you should be able to confirm the diagnosis yourself.  Pop the
hood (cold, non-running engine), reach in there and try to jiggle the
crankshaft pulley.  If feels tight, and all the fan belts look properly
aligned, fire up the engine and let it idle.  Then look at the pulley and
belts.  If the pulley is loose and/or wobbly, then you've likely confirmed
the problem.  If the pulley is running true, I'd be looking askance at your
dealer.  I'm not sure how they could have diagnosed a broken crankshaft nose
if the crankshaft pulley is true and tight.

I looked over your earlier post, and no one mentioned the catalytic
converter.  I had a cat plug up with a Nissan I had once, and it surely
caused a large loss of power.  If that turns out to be the problem, I'd also
replace the O2 sensor, just on the principal of the thing.  It's probably
been a bit hotter than it likes.

Cheers,
Walt

It's a known problem and somewhat common unless timing belts are changed
properly.  Can you see it wobble?  Read the article on miata.net for
detailed information and how to tell if you might have the the problem.
 As for the $2100.00, that might be the right price but it's not the
route I would go.  I've bought two engines off of ebay without a problem
and a recycler would probably sell you a good engine for $1000 to $1500.
 Be nice to find a lower mileage engine out of a recent wreck for half
the price (assuming you could do the swap yourself - it's not hard when
it's a direct swap).  If you do go the used engine route, remember the
problem afflicted all 90's and some 91's so check the VIN number of the
car carefully to make sure you're not just buying the problem again.

Tom
92 Red

Depending on how bad things are, it may be fixed by using either Loctite
products or JB weld. My keyway was gouged out about 250% when I gooped it
all back together about 10K miles ago. It is still running strong.

It is important to use a new crankshaft pulley;  comparison and measurement
of the old and new revealed the absence of a 1mm relief in the original
pulley where it sat on the shoulder of the crankshaft. This appears to have
caused the pulley to rub on the engine housing which likely was a
significant contributor to the keyway problem. The new pulley seems clear of
everything.

If you ignore the problem, you probably run the risk of further damaging the
crank nose. There have been cases where the pulley sheared off. Of course,
that means your Miata comes to an immediate stop. At that point, the only
solution will be a new crankshaft.

To answer your questions:  Yes, it is common;  price sounds right;  my
preference would be to use the engine I have known for the past 168K miles
or start new.

Hope this helps.

Ken

simple.Takethe camshaft out  yourself.Have it machined, also get bigger
bearingsthat will fit  the machined crank.  It costs around 120 -200 to
do this.Worked wonders on my cavalier. I installed it.  I also bought
new engine seals while I was at it.

-hector
Mx3 gs

http://community.webtv.net/hgallegos/HectorsPicturePage