1990 crankshaft gone!

I have a 90 with 103K on her and noticed she was suffering from a severe lack of power. Posted symptoms to this group and received great advice. I did some trouble shooting (plugs, wires, air cleaner...), but still no improvement in performance. I took it to the local dealer who informed me that the crankshaft was going. He said it was common with the 90's, something to do with the "key". Quoted a price of about $2100 to fix! Since "top-down" weather is just about over here in the northeast, I'm thinking I'll be saving money over the cold months to have her fixed in the Spring.

3 questions: is this a common problem, does that price sound right, should I get a new engine instead?

Thanks in advance for inputs.

Jeff ....a very sad 90 Miata owner today....

Reply to
Jeff & Missy
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  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.
Reply to
Lanny Chambers

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

Reply to
WJ

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

Jeff & Missy wrote:

Reply to
Tom Howlin

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

Reply to
KWS

Cam timing is out of whack. Actual ignition timing is retarded too, although you can't tell via timing light as the mark moves with the cams.

Common bug. Mine (also a 90) broke like that. I also fixed mine with loctite and it lasted quite a long time (several years). Do it yourselfers fare best with this problem. It cost me about $50 for the parts and my labor was free. A shop might have charged $600 if one could find a shop willing to do a goop repair.

Later, I did buy a used engine for $800 and installed it myself when the first repair gave out. It was an education and not as hard as I thought. A shop might have charged $1000 for labor. While a used engine is less expensive, a dealer would not install a used engine and I don't blame them. Too many risks. For $2100, they will likely pull the engine, put in a stronger crankshaft and be able to warranty it.

Nonetheless, it's a shame. A 90 with 100K miles is barely worth $2100 wholesale. One could buy a used miata and part out the old one and spend less money. In hindsight, throwing $1000 at mine was money I'll not get back.

Reply to
merle

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

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Hector Reports Spam

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