67 twin turbo dart

subcom said

From your description and the fact that adding the filter helped makes it sound like interference from some where. How did the crank tooth log look? Did you capture a composite (cam and crank) log also? Any gaps or drops in the graph where it lost sync? Electrical gremlins are a pain. Process of elimination. Just work thru all the potential sources one by one, you’ll get there.

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It actually first did it with filters off and again with filters on. Oh yeah there was drops, the graft looked like when you start the engine, rpm was would drop to 0 and back up, it was weird. We did send both composite logs with and without filters. It sounds like Matt at diy thinks it the old style hall effect and why they went away from them, needing to be much closer to the tooth wheel compared to their and others sensors.