Engine Speed Trigger

Link G4+ x - 88Nissan 300zx - trying to resolve Engine Speed Fluctuation. Nissan optical CAS, swapped 360 to a 24+ disk. 2000rpm -3000rpm - up to 100rpm to 200rpm swing, 3000-4000 - up to 200 to 300 swing, 4000-5000 - up to 300-400 swing, 5000-6000 - up to 500 to 600 swing. Watched webinar 95 & 96. Helped but did not resolve. Need some guidance.

So, is the engine speed actually changing (so a misfire or severe timing change), or is just the engine sensor indicating a change when none is occurring? Are you observing this change on the laptop connected to the ECU (so you could log it and share that), or is it just on a tachometer?

What conditions are you testing -- unloaded free-reving? Steady state loaded -- either driving on the road, or on a dyno?

No backfire, smooth running. See photo of log attached

More - engine speed is smooth, no backfire, photo of log attached. Light load driving, no high rpm log done, yet. Lap top rpm gauge flutters like the log. Should I attach the log file.