No Spark, RPM's disappearing
 

So I got my MS up and running but ive run into the same problem as listed here; https://www.miataturbo.net/forum/t28781/

When I start cranking I get an RPM reading for about 2 seconds then it drops to 0. I get no RPM reading or spark during any subsequent cranks unless I turn the key to the off position first. I attached a datalog of the behavior.

The car runs great while the stock ECU is plugged in so I know my ignitor/coil is fine. Although I gathered it may be a weak CAS from searching through the forum.

Ive reflashed multiple times with no change.


Any ideas or suggestions on where to go from here?


(MS-I v3.0, Standalone with idle mod, MSnE 29y4, MSPNP base map on a '90 1.6L with 200K+ miles)

Has the ignitor been getting hot?

No sir, not even warm.

I would check the wiring at the CAS first. This sounds like an input problem and not an issue with the igniter.

You have all the mods done to make the CAS work with MS? 2nd trigger and all that?

How to MegaSquirt your Mazda Miata check all that shit

Checked all my connections, rewired the miata CAS mods, resoldered everything that looked bad, and still the same problem.

I bought a jimstim and hooked it up to see if it was my CAS but even with the stim I get an RPM reading for a brief moment then nothing at all. (Have to reset to get another brief reading)

Jimstim has the miata signal jumpers so its outputting the correct waves.

Could it be a bad IC somewhere? Or possibly the CPU itself?

I'm thinking you may have reversed the cam and crank signals. Try switching them. Also with the MS installed check for 5V on the cam signal pin on the CAS plug and 12V on the crank signal pin if you have these voltages then your pullup mods are working If not then they are faulty. Thinking input circuits, the most likely thing to go would be the opto-isolator 4N25 (about 25c from radioshack) If you have access to a scope that will really help you to find where the signal is ending.

So I ended up checking continuity between IAC1A and pin 25 and was getting high resistance as well as continuity with most of the other DB37 pins so I just moved my CMP signal to IAC1B. (Zero resistance and no continuity with anything else)

Checked with the stim and everything appears to be working great.

Thanks guys. Now on to tuning, first start with the MSPNP base map has it idling pig rich.