Car shutting off and on randomly while driving

[psulja]

That's what I've been thinking it might be as well. A loose connection somewhere or even a bare wire touching metal somewhere, the problem is trying to find exactly which one it may be. The fact that power to the entire car is lost is making me lean more towards something to do with the wiring for the alternator.

A little background on the alternator; it was replaced in September 2010 by a shop. In 2011 the car was still having charging issues and just before I bought the car we took it back to the shop exactly one year after it was replaced for them to do it again under the 1-year warranty. They went through 2 or 3 alternators because they kept having issues with it not charging properly. Whenever it rains the battery light also comes on every now and then. That leads me to thinking maybe the problem wasn't actually the alternator but the wiring instead.

The problem right now is that I'm working 6-day weeks for the next couple months so I don't really have any time to find the issue. I might have to just park the car and start driving the NA for the next little bit so I can take some time over the next little bit and fix all the issues that have started to come up with the car recently.

[psulja]

In post #7 you said you "played with the wires" and that the problem seemed to go away for a little while. What wires? Spark plug wires? Also you said the instruments all go to zero but judging from the jumpy video, the only thing I see going to zero is the tach which is normal if it's reporting sudden loss in RPM. The other gauges, of course, wouldn't jump to zero anyway and the ODO seems to retain power so it's not a sstem-wide electrical outtage.

Given that the radio cuts out, I think it's something related to the ignition switch. Perhaps it's the switch itself or the wiring to it. If it weren't for that detail about the radion, then my suspicions would be plugs, wires or cam sensor.

Sorry about not being clear about that; the wires leading up to the alternator as well as the alternator connector; I was just moving them around a bit to try and get a good look at them if they had any exposed wires showing. After that it started right up. I didn't see any exposed wires when I checked them, but that was a quick check at the side of the road.

I realized after I posted that that it was just the tach dropping to zero and the car losing power to the radio, but when it died on me and I had to pull over the hazards still worked. But in one of the videos i posted you can see the turn signal flicking on and off quickly with the battery light when I was coasting towards a light getting ready to turn left.

[psulja]

Okay, I checked quite a bit of the wiring in the engine bay and saw no exposed or frayed wires. Checked connectors to make sure they were completely on; none were loose. Check the ground to the ppf, it was good. Checked my battery terminals, both were tight. I still need to check all the grounds once I find them.

I guess I'll move on to interior wiring under the dash after that to see if there is a loose connector? I had the resistors for the airbag light come loose so maybe something else under there did as well.

I did notice my trunk leaking so I'm not sure if that water could have affected anything. It's been dry for the past little while (couple weeks).

The car almost died on me again on my way to work. Well it did die but I was right in front of work so I just coasted into my spot, then when my shift was over it started fine.

I do notice that it happens a lot more on acceleration and not as frequently while just cruising. If I put the clutch in it stops the issue almost always, except when it is really bad and the car is completely dying on me.

[— kung fu jesus —]

I woulf check the harness near the ECU. See if it has "been into" by a previous owner for, say, a powercard install for a s/c.

[psulja]

I'm good friends with the PO and have known the car for pretty much it's entire life, there has never been a SC installed, but I'll still check all that wiring tomorrow anyways just incase something else is wrong with it.

[joe morreale]

When my crank sensor started to go I was getting intermittent stalls. Sometimes it was just a mater of popping the clutch to start it while in traffic. I never just let it coast to see if it would run on it's own like yours. I got no codes for 6 months. Mine would die under all conditions, acceleration, cruising and idling. Always after about 5-10 minutes of driving. Then it would happen for a week. Electrical gremlins are frustrating I hope you get yours figured out easily. Are you sure the battery is secured tightly? They have been known to move during acceleration and ground out the system. 2001 miata

[— kung fu jesus —]

Does this sound like your issue?

http://forum.miata.net/vb/showthread.php?t=389007

I was also thinking about the main relay...the CKP (crank position sensor) wouldn't cause the electrical cut you describe.

This thread sounds more like your issue:

http://www.miataturbo.net/showthread.php?t=64489&page=2

This was an interesting fix for the main relay...

http://forum.miata.net/vb/showthread.php?t=389854

Here is a pic I took for checking the continuity of the main relay. The 99-00 service manual came with my wife's NB.



The CKP inspection involves checking the air gap with a feeler gauge. Let me know if you need that. Diagnosing the sensor itself needs a specialized electronic tool.

[psulja]

Wow, thanks KFJ! I think it might be the main relay. I'll have to see how the connection is on it and possibly even buy a new one. I don't really understand wiring diagrams all that well, how do I go about testing the continuity? Would I put one lead on A and the other on B, and then one on C and the other on D? (Don't mind the noob question lol!)

@Joe, it could be the battery moving to be totally honest, it is a battery from my NA that fit snugly in there but not so snug in the NB. It doesn't help that my trunk is leaking right underneath the battery and from the rain rail a bit forward from the battery.

So things I'll try next; test/replace or check how tight the female spade connectors are on the main relay, try to get the battery completely tied down so it doesn't move at all, and try to stop the leaks in my trunk lol.

Thanks for the help guys!

[— kung fu jesus —]

Paul, testing for continuity would probably only be helpful if it stopped altogether and didn't come back on. Because your issue is intermittent, it leads me to believe it's a loose connection.

I had to think about it for a little while. A bad CAS or CKS wouldn't cause the electronics in the entire car to switch off like that. A CAS would throw code, the CKS usually won't. If the battery was bouncing around, you would hear it. I sort of took it from there and used some logic to google search.

Your relay may not be bad, but the female socket it connects into may have flattened out, causing a bad/loose connection. I suggest using this guy's solution first:

"1) Remove relay from socket.
2) Look at the socket, you'll most likely see that the receiver slots are a bit stretched, which causes to make poor contact with the relay pins, hence when you hit a bump, contact is broken and the car dies for a second.
3) Take a small bladed screwdriver or pic and tighten up the female ends of the connector in the fuse box just a bit.
4) Reinstall the relay, you'll feel the extra resistance as you push it in, don't worry, that just the spade connectors making good contact."

[psulja]

Okay, that makes sense about it being loose leading to the problem being intermittent and mostly happening over bumps. I'll go try that now and see how tightly the relay is held in there and tighten it up if necessary.

[— kung fu jesus —]

Jiggle the handle too.
It works on the toilet.

[psulja]

lol.

I checked how tightly it was held in there; it wiggled around a little bit so I pulled it out and closed the female spade connectors a bit more and pushed it back in. We'll see how well this works.

Come to think of it; when I was checking all the wires in the engine bay, and I cleaned out the trunk at the same time, I pushed down on all the fuses and relays there to make sure they were fully seated so I probably pushed it down enough that it fixed the problem temporarily which is why it hasn't happened that much in the past couple days.

I'll see if I have any issues over the next week or so to see if that really did fix the problem.

[— Agent☣Orange —]

That's what I was getting at earlier about the radio. If it stayed on during the stumbling, I'd be thinking plug wires or sensor. Since the radio cuts out, and that's a critical observation, it must be an electrical connection in the ignition circuit, especially since it happens over bumps and higher RPMs (accel) with resulting harsher vibrations. So, it's down to relay, fuse, ground point, ignition switch or harness plug somewhere. Maybe the big one under the steering column.

I worked on a Miata with similar problems and turned out it was one of the two big white wires coming loose inside the ignition switch harness connector under the steering column.

[psulja]

If this main relay fix doesn't work I'll have to check the wiring under the dash, but the fact that I fiddled with that relay and wiring in the engine bay and the problem went away for about a week it leads me to suspect something that I touched while in there last time; the main relay being one of those things.

[— Agent☣Orange —]

That would make sense. You jiggled the wiring on the alternator too didn't you?