Megasquirt 3 MS3X lost sync. 1992 Mazda MX5/Miata NA6 1.6

[Rothko]

Firstly, thanks to these great communities I have been able to get my car back up and running many times before. Thank you.

Yesterday I was happily driving my Mazda MX5 NA6 Turbo with MS3X ECU with no problems. I stopped the car leaving the car running and plugged in my laptop to tune the fuel tables and pretty soon after that the engine cut out and wouldn't start.
I ran the composite logger which shows a good clean CAM signal but no CRANK signal at all.

I have had a similar problem before that was fixed by tuning the pots so I tried that but to no avail. I checked the harness and grounds which seemed fine and so decided that it must be the ECU (that I had built).

To get the car home I put the stock MAF, TPS and ECU back on and the car ran really rich (using 265cc injectors and fueling mods) but consistently rich - 9.5 at idle and the timing jumped about between 8-12°BTD. With no other options I limped it home (3 hour drive) like that.

I will have to leave the car until the weekend but in the meantime I have some questions that I hope will eliminate some possibilities.

1. The crank and cam signal come from the same sensor on the NA6 right? so does the fact that I'm getting a clean cam signal mean that the sensor is ok?
2. When reverting back to stock I found water inside the MAF connector that I had taped up - could that water cause a short that would mean I lose crank signal?
3. Could simply plugging in the laptop make any changes to the tune without clicking 'burn'? I had just had a few problems getting TS to run and had to uninstall the new Java update to get to run. I'm not sure if this is relevant at all but wonder if the tune could have been corrupted by the computer.
4. Does the fact that it runs (although pretty rough) on the stock ECU eliminate harness problems? Or any/many other problems?

[Matt Cramer]

Firstly, thanks to these great communities I have been able to get my car back up and running many times before. Thank you.

Yesterday I was happily driving my Mazda MX5 NA6 Turbo with MS3X ECU with no problems. I stopped the car leaving the car running and plugged in my laptop to tune the fuel tables and pretty soon after that the engine cut out and wouldn't start.
I ran the composite logger which shows a good clean CAM signal but no CRANK signal at all.

I have had a similar problem before that was fixed by tuning the pots so I tried that but to no avail. I checked the harness and grounds which seemed fine and so decided that it must be the ECU (that I had built).

To get the car home I put the stock MAF, TPS and ECU back on and the car ran really rich (using 265cc injectors and fueling mods) but consistently rich - 9.5 at idle and the timing jumped about between 8-12°BTD. With no other options I limped it home (3 hour drive) like that.

I will have to leave the car until the weekend but in the meantime I have some questions that I hope will eliminate some possibilities.

1. The crank and cam signal come from the same sensor on the NA6 right? so does the fact that I'm getting a clean cam signal mean that the sensor is ok?

Not necessarily. The two sensors are in a single housing and share a common power supply and ground. However, it is possible for one sensor to fail and not the other - and it is very common to see the connector fail, in which case one of the wires may develop an intermittent open circuit before the other.

2. When reverting back to stock I found water inside the MAF connector that I had taped up - could that water cause a short that would mean I lose crank signal?

No.

3. Could simply plugging in the laptop make any changes to the tune without clicking 'burn'? I had just had a few problems getting TS to run and had to uninstall the new Java update to get to run. I'm not sure if this is relevant at all but wonder if the tune could have been corrupted by the computer.

Not on the latest firmware. Some earlier codes (1.1.x and earlier) could corrupt the tune if bad data was sent. (Note that buttons like "Use the offline settings" can send a new tune to the ECU; it's not just the "Burn" button, but the intent should be clear.)

4. Does the fact that it runs (although pretty rough) on the stock ECU eliminate harness problems? Or any/many other problems?

It suggests they are unlikely but sometimes not impossible.