No start with MS plug in - Stock ECU for fuel and spark

[MiataMath]

Hello all,

I have finish installing my megasquirt (MSnS-E) in my Miata 96. (Megatune 2.25b717beta).
I'm sharing signal with the stock ECU for TPS, NB 02 and CLT (changed value with EasyTherm). I have a GM IAT tie-wrapped to the air filter.

I'm tapped on the stock ECU harness for power, ground and all of the signal (except for the IAT where I ran a wire to it and tapped the MAF harness for ground)

I have not yet plugged the Injector In neither the coil output.
My board is modded with the DSM mod for the CAS we are using.

The problem I am having is... the car doesn't start with MS plugged in but when I unplug it, it start..

With the engine off and MS plug in, I get all my signal in Megatune. The only small weird thing I have notice is my O2 signal seem to move with my TPS. But only for the first few minutes.. it stop doing this afterward.

I can get the car to sputter.. sometime getting to 600-700 rpm for a second then dropping back to cranking speed.

Is there anything to configure when I'm not even using Fuel or Spark yet?
What could cause it to not start?


I'm really lost there.

OH.. and when I unplug MS and take my car for a spin under the stock ECU, I have a check engine light.

Any help or suggestion would be really helpfull.

[MiataMath]

Hello all,

I found the no start problem and the O2 glitch.

The glitch got solved after reflashing the ECU.

And the car start right back when I unplugged the RPM signal (CPK and CMP) and only plugged one of them back.

Seems like I can't plug the two of them on a piggyback install.
As soon as 1 is unplug, the car started right back with the correct RPM reading..