A shot in the dark. I know you're new to the area but, if someone from the local Miata club has a 99/00 that they could let you plug your megasquirt in, that would eliminate you having to buy a car. After hearing all you've done I would consider the megasquirt suspect.

When this started happening to me, someone suggested tightening the valve cover bolts. Sure enough, mine came loose after a track day. Not saying it's the end-all be-all but it's a cheap check.


I might also have a Ballenger crank/cam sensor with upgraded wiring that I never installed. I'll have to hunt for it if anyone is thinking of upgrading.

Have you gone through the cam/cas pot voltage measurements as Hector mentioned?

MS3XV30_Hardware-1.5 page 94

I'm sure Brian's trubokitty writeup will do a better job of walking you through this. You really should measure the cam/cas read-in circuit voltages and make sure this isn't a simple resistor setting.

I strongly suggest adjusting the pots like this:

Step 2: fine adjustment of the VR circuits:
– For the main board, measure the voltage on the upper leg of R54 while turning R56.
– For the MS3X board, measure the voltage on the lower leg of R17 (close to U7) while turning R11.
In both cases, you want to see about 2.5 to 3 volts at that point, which puts you right in the middle of the actual output range of the sensors.

Thank you all for the input, I really appreciate it. I hate to think of ripping this thing apart when it runs really good... until it just doesn't run at all. I know it has to be some stupid little issue.

I have not adjusted the pot voltage. I assume it was a combination of not having any idea what Hector was talking about and failing to come back and research after initially reading his post.

Thank you so much again for these tips. I'll pull the MS out now, check the adjustments, and then see if I can come up with some way to get it powered up in the car and check those voltages with the case off. Damn you NB and your terrible ECU location!

Well now I totally screwed it up. Car won't start at all now after trying to adjust the pots. If anyone feels like they'd be capable of fixing whatever I've screwed up just name your price I guess. I took a log trying to start the car. I can get more diagnostic logs if they would be helpful. All this stuff is way over my head.

I know it doesn't feel like it now, but this is actually a really good result. You made a change to something and the system responded!
It's been a loooong time since I've viewed a composite log and it seems that my MLV doesn't want to open your whole csv file.
Assuming you never achieve sync, then we need to look deeper into what is going on with the CAS/CAM input circuits.

Did you measure the voltages on the test points mentioned in the writeups?

Thanks for the pick-me-up. I tried to measure voltage, but I just couldn't get it. Between trying to get everything positioned, not really having any idea what I was doing, laying under the dash, finding a ground, and getting the multimeter on the right spot, after several attempts it just wasn't going to happen. I pulled the MS back out to try and readjust the pots again following Brain's MS3X Assembly Writeup under the expander board section.

My fear at this point is that I didn't identify the initial problem, I just created a totally new problem in addition to the initial one. I guess we'll see how attempt #2 goes. Oddly enough, I'm much more confident working on something that's known to be 100% broken vs something I suspect to be 10% broken. It's not like I can break it anymore than it's already broken.

Same result after attempting to re-adjust pots. Car doesn't sound like it wants to start at all, but it is reading rpms in tunerstudio.

Like I said, I've really got no clue what I'm doing. I took a video if someone wants to review, maybe I'm completely screwing this up somehow.

I'm not sure how much needs to be reading in order to get a tack readout. That might indicate cam and crank are reading.
There are pots to adjust on the mainboard as well (for the crank sensor).

I'll try to remember the details of the composite log in order to help out a little more.
Some general debug flow:
If all of your ms inputs are working, then go through the output test modes and make sure those all work (spark,fuel,etc).
If the inputs and outputs check out then something is off with settings or the firmware.