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Unstable tach reading


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Hi Adam,

Well, after a catastrophic failure of my original EZ36 (struck by lightning internal casting failure), and buying a JDM engine which had serious valve train issues (in part due to apparent plugged oil gallery), I'm finally back on track with a newer and lower mileage engine. 

All looks good, am using the same setup which had my original engine running very smoothly.  The engine is reluctant to start and run requiring a little throttle to do so and then runs rough-ish, not idling without throttle, blowing a some smoke, and not responding well to throttle. 

Everything looks fine with signals from both triggers (did get some trigger errors initially but none after started running) but the tach reading in the program is jumping all over the place as is the tach in the vehicle which is run from the ECU.  

Is this likely a Trigger 1 issue again?  I did take this opportunity to replace my repaired trigger wheel with the new one I sourced and am using my new trigger sensor so I'm actually relatively confident in them.  As noted, the ECU gives a green for trigger signal.  

I am using the wiring loom which came with this new engine (which is in very good condition to inspection) and will check all the connections as this seems like a failing or broken wire/connection to me.  Any other thoughts what this might be or other things I should check?

Thanks in advance,


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Sorry, wanted to do a couple of things before sending setup and log file.  

Today I wired the crank angle sensor directly to the ECU loom worrying maybe I'd disrupted the wiring changing engines.  So, new plug and shielded wires directly to the shielded wires of the ECU wiring.  Continuity tested from plug at sensor to ECU plug and all correct.  

No change in behaviour of tach and poorly running engine.  

Borrowing my friends oscilloscope and will take some oscilloscope pics tomorrow to make sure there's nothing funny about the tracing.  Honestly, new wheel and sensor so I can't see why there should be a problem.



What am I missing?  When I go through the runtime charts everything looks as it should but there's something odd happening.



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Well, I didn't really need more evidence of this but I'm an idiot. 

I had wired Trigger 1 directly to the Link loom (as it is today) when troubleshooting before and, while waiting for my new engine to arrive in Oct and in an effort to tidy up the install, I returned the wiring CAREFULLY to stock.  But not carefully enough. 

Oscilloscope today showed I had managed to reverse the polarity of the sensor.  That noise you heard a few minutes ago in New Zealand was me slapping my forehead here in Canada.  

Returned the wiring to correct and now runs great.

Sorry I've wasted your time...turns out my kids have been right all along.  I'm not telling them about this.

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