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-   -   Cranks but won't start (https://www.miataforumz.com/nb-1998-2005-7/cranks-but-wont-start-2506/)

rododle 09-21-2017 02:26 PM

Cranks but won't start
 
The following is what was going on before it completely quit. As told by my daughter. I changed the fuel pump before I read up on what I needed to check. It wasn't the fuel pump. A neighbor brought over a spark plug and we checked for spark but there wasn't any.

she would come to a stop sign, where usually she's able to leave it in 2nd gear and pull out, it would bog down too much, so she'd have to rev it quite a bit. It did that 2-3 times. Other than that, it ran just fine in town. Once she was turning on to hwy 10, in 2nd at the stop sign, it bogged down again. So as she's driving on 10, the rpms (usually at 60mph, stays on 3-4 rpms) dropped between 2-3. Then the battery light started flashing. It never overheated, no other warning lights came on, oil pressure stayed in usual range. The rpms did that same thing a couple more times with the "battery" light flashing. That's when she pulled over to call me. She killed it and restarted 3xs. It never dragged when starting it. In fact it started easier than usual. So, I told her to turn off a/c and try driving. She did and it was fine all the way home. The only other thing she has noticed, not that day, was a tinny noise when changing gears.

A guy is coming over today to put his computer thing on to see if it will tell what is wrong. Any suggestions?

Jerry L 10-21-2017 05:19 AM

Hmmm... you got a brain teaser here for sure! Well, it is clearly an electrical problem since the battery warning light was flashing and the "no spark" you have already tested for, so my guess would be the coil.

Since this happened quite a while ago, did you ever find out what the problem was, or is it still broken? Please let us know what the deal was, K?

Redcap 10-28-2017 04:00 PM

Sounds like a charging problem and it can be difficult to diagnose if you throw parts at it. If the belt is loose on the alternator, or the alternator is dying - unless you use a voltmeter, you may suspect (as I did with my dying Miata), that you just needed a new battery, for example. Throwing good money at a new Battery, it worked well for a while and the of course died - it was basically making up for the poor output on the Alternator. I'm wondering turning off all the accessories allowed your daughter's car to limp home.

My other guess would be the crank angle sensor. They tend to slowly die out, rather than just completely fail. I'd have stints where the car would completely shut off in the middle of driving, or stutter in RPM, then just start driving again. Thank goodness the car naturally fires off again when in motion.

If you have a 99-00, as Jerry mentioned, it could be the coil packs, they have a tendency to fail due to heat. I did some voodoo that has yet to prove itself, but I did put some fiberglass heat shielding material between the coil pack brace on the engine (clamped by the two 10mm bolts on either side), and have not had a coil pack failure since.


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