- Thu Aug 06, 2020 3:14 pm
We don't know where the firing failure is, so diagnostics. I would start simple, by first determining if the "misfire" is occurring before or after Speeduino. Use a 'scope, digital analyzer, or even a timing light to confirm if any spark plug firing sparks are actually missing. If they are all good, then it is more likely HV circuit condition (damaged connection, coil, wire, spark plug, etc) or fuel-related.
If some sparks are missing, then work backwards to find if the coil driver signals are all reaching the ignition coils. If signals to coils are all there, then likely connections, coil driver or settings are bad.
If signals to the coil drivers are missing, and connections are good, then test for trigger inputs to Speeduino. If signals are all perfectly good, and of proper polarity, it is either a settings issue in Speeduino or a board issue.
This last one is very dependent on your sensor types, input conditioner (if any), and settings to use those properly. For example, if you have two VR sensors, then both Trigger Edges should be the same (Rising or Falling) depending on the conditioner used. Missing-tooth wheels should be reading the teeth falling edge signal, and settings made for that. This can be confusing, so please post your sensor types, conditioner used, and jumper settings. A tooth log could also be useful.
In this example I worked backwards from the spark plugs to the input sensors, however you can start at either end of the process (input first or output first), but don't skip any testing in-between. The concept is to test if (in->out) operation is good until it goes bad, or (out->in) it's bad until it's good. This is a way to locate and confirm (diagnose) the source of issues. Each test brings you closer to the real problem without guessing. Good luck!
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