Intermittent Sync Loss MS3x
 

My 2000 Miata with MS3X has been randomly turning off the last month or so. I'll be sitting in traffic and it'll die, or driving down the road and randomly lose all power. If I'm stopped sometimes it'll start back up immediately, sometimes it won't start for a minute or two, then fire right back up. If I'm rolling I can usually put the clutch in, release it and it'll crank back up. This happens around one time per hour of driving and under completely random situations (warm/cold motor, accelerating/cruise/idle, sunny/raining, etc). Other than this once per hour occurrence the car runs great with no issues.

I seem to remember seeing both sync loss reason 31 and 32 (2 cams not seen, 0 cams seen), but it's been a while since I've gotten a data log of it. I've replaced both the crank and cam sensors, adjusted the crank sensor multiple times, and checked wiring for any frays/cuts immediately around the sensors. I'll start to think it's fixed, then it happens again. I'm going to start logging all the time now so I can get a log of it to share, it's been a while since I've captured it now.

Any other suggestions on what to check or things to try? I'm a little lost at this point and driving the car is pretty terrible now since I'm always waiting for it to just randomly die and leave me in the middle of traffic.

Is it when the car is hot? Possibly need the upgraded CAM sensor that ballenger motorsports sells.

It happens in all conditions, totally random as far as I can tell. This morning it died about half a mile from my house at 75 ambient temp and 120 water temp.

I finally got a datalog of my issue. This afternoon, I leave from work, a few seconds later it misses a bit. By the time I get my phone connected I've got 4 counts of sync loss. After that the car runs fine. Just over 5 minutes into my drive I'm cruising at 65mph and it just dies. Tach drops to 200rpms and holds for a few seconds before blipping to 780rpms and then flat-lining. This is while the engine is still mechanically turning ~3000rpms. After a few seconds I throw it in neutral, try to recrank the car and still get no tach signal. Pull off the side of the road, cry for 2 minutes, then the car cranks back up and drives the remaining 15 minutes home without any issue.

This happened again right at 1 hour drive time since the last occurrence. Totally random conditions, rpms, temps, etc.

Datalog and tune are attached. If anyone has any suggestions at all, even stupid ones, please throw it out there. I'm open to try anything at this point.

https://cimg9.ibsrv.net/gimg/www.mia...c9dde5bdcd.png

kinda sounds like the cam sensor is failing.

I've replaced both cam and crank sensors.

Run a tooth log and a composite log and post those.

I screenshot both a tooth log and composite log, it didn't look like I could save the log itself. The issue is so rare I wouldn't expect it to show in either log, but I wouldn't know what I'm looking for either, so hopefully you can see something there.

I'm still chasing this issue. I found an ancient thread with similar issues and people discussing replacing the stock cam sensor with an Evo 8 sensor. I gave that a shot, ordered the sensor and swapped it. The car runs fine with the Evo 8 sensor just have to wait to see if the issue comes back again.

We used to have the sync issue but it was definitely a heat related issue. I think that people who swapped to the EVO sensor was for the heat related issue also. But since the heat related issue is nothing more than a connector being placed too close to the heat source then it is really a connector issue which means it could happen intermittently even without the heat present.

So maybe just do what will ultimately fix the connector issue and get rid of it and solder up the the connection to the cam sensor wires which ultimately fixes the issue as has been proven in SM. You can use it with a connector like the SM solution or just leave it as-is since the cam sensor is a one bolt disassembly and can stay as part of the harness when unplugged. Our cam sync issues magically disappeared with this solution.

Thanks for the help and suggestions, especially identifying the cam sensor as the issue.

Just wantrd to update that the evo 8 cam sensor seems to have **NOT** cured the problem. It's been 2 weeks now with no issues at all after 2 separate oem sensors gave me issues. Best of all, the evo sensor was plug and play and dirt cheap, $14 on amazon prime.

*Edit - Problem returned yesterday afternoon and again this morning. :(

Link or P/N, please.

It's part MD327107 and fits a ton of different cars.

https://cimg8.ibsrv.net/gimg/www.mia...1c8029d128.png

So I'm back to beg for more help. The car started dying on me with the new Evo cam sensor, just like before. I ordered a new cam sensor clip and pigtail and spliced it in, but the issue has continued.

I know several people have suggested this is a cam sensor issue. After trying 3 sensors and replacing the harness clip, is that still the consensus issue? I'm ready to start pulling the intake manifold so I can trace the wiring back toward the ecu.

I just wanted to see if there were any other things to investigate before I start pulling the wiring harness apart.

https://cimg1.ibsrv.net/gimg/www.mia...e2335810dc.jpg

Start by doing this. If the issue is lost sync because of heat or otherwise messing with the cam signal, this is the fix.

I hardwired the harness to the sensor as suggested and still had the same issue. I'm absolutely confident at this point it's not the sensor or harness plug.

I've run 3 OEM Miata cam sensors, an aftermarket Evo8 cam sensor, and an OEM Evo8 cam sensor. I've run these in various combinations; hardwired, with my stock harness, an aftermarket harness, and a stock Evo8 harness. No amount of pulling, jiggling, wiggling of the cam sensor harness with the car warm or cold has been able to duplicate the sync loss issue. All combinations of sensors and harnesses result in the same intermittent and completely random car cutting off. Each time this has happened the car will restart and run fine somewhere between 5 seconds and 3 minutes later.

I pulled the intake manifold and de-loomed the wiring harness all the way back to the firewall. None of the cam wires show any kind of physical damage. I really feel like I can discount this being a cam sensor issue, unless it's at the ECU. Just not sure where to go from here. If anyone has additional suggestions I'd greatly appreciate it.

Who built the MS3X?

Brain built it. I'm not at all trying to suggest that it is an ECU issue, I'm just lost as to what my next steps should be.

Any news? I know you are trying to diagnose it as a connection/wiring issue which is reasonable. Maybe just start cleaning off all the ground points.

I would say to also do a re-adjustment of the ign signal pots. Just a shot in the dark as maybe resistance in the wiring building up over time may affect the adjustment.

I just wanted to bump this, hoping for some guidance. I've been fighting this crap for a solid year now and I'm over it. The car keeps randomly cutting off, logs read 200rpms, no spark or fuel, then 30 seconds later it will fire up and run like nothing hapened. I haven't been able to actually enjoy the car in a long time. Everyone keeps saying, "It's your cam sensor" and I've been through probably 10 of them now. I've also tried multiple crank sensors. I've spliced in a 2 different cam sensor harness. This is 100% NOT heat related, I've had several times it's happened within a minute of a cold start, with coolant temps well below 80 degrees. Lately I've been focusing on grounds, I've moved, checked, and changed every ground I can find and it still happens.

The issue appears at times 100% random; it's happened under load, under cruise, at idle, cold, hot, at high rpms, at low rpms. It's run probably 400 miles without an issue before, it's gone 15 seconds between recurring issues. It's shut off when I've hit a bump, it's shut off consistently at high rpms for a while, then it just went away. This morning it almost killed me when it randomly shut off cruising as I frantically I tried to swerve across 4 lanes of I75

I'm over it and I'm ready to make something happen. This car is beyond going "back to stock". I have 3 options as far as I can see:

1. Buy new Megasquirt and see if that fixes it
2. Buy new miata and swap over my megasquirt to see if the issue follows the car or the MS
3. Partout everything and start over again

Any thoughts? Suggestions? Halp!