MSefi.com read only forum (Jan.15,2018)

From looking at this log I am unable to determine what is cause and what is result.
The problem is the RPM randomly drops to 0 and sometimes stalls. I can see that the
trigger signal changes but I don't know if this is because the ECU has a glitch or
the trigger is failing. The trigger also continual drops. Is this normal
The TP seems to change yet the peddle is not being touched.
I had a timing light connected and the light does not flash at each drop out.The O2
sensor does not indicate richness following a drop so I don't think the injector is
firing either. Please see attached log.
The engine is warmed up. This is an old (2) cylinder engine with TB fuel injection and a MS2.
I was hoping someone with more experience could determine what is happening.
Thanks for any help.

What is the ECU using for RPM input?

Matt Cramer wrote:What is the ECU using for RPM input?

4" 36-1 tooth trigger wheel made in a machine shop. The sensor Hall sensor from DIYAutoTune.

If it's our threaded sensor, try tightening up the sensor gap a little.

It is not the threaded body version. But I can adjust the gap. What is a good gap size?

Thanks Matt.

As tight as possible.

I moved the sensor in from 0.050 to 0.020. I am not sure how perpendicular the sensor is to the wheel or how concentric the wheel is to the crankshaft. The engine now drops out more consistently so I think this is the problem I need to solve first.
Can I read the output of the hall sensor with a with an automotive frequency meter??
See attached log with relocation of the sensor.

Thanks Matt

A frequency meter isn't likely to work; the best tool for the job would be an oscilloscope.

I reworked the mounting bracket for the hal sensor and now there is about 0.004 to 0.008 clearance. I cannot make it more concentric because it is aligned with a bolt. If the RPM is greater than 1400 there is no drop out. At idle it still drops out and each time the value of trigger signal goes down. Why is that occurring? What should the value of the trigger signal be?? Mine ranges from +18 to -2.

708803 wrote:I reworked the mounting bracket for the hal sensor and now there is about 0.004 to 0.008 clearance. I cannot make it more concentric because it is aligned with a bolt. If the RPM is greater than 1400 there is no drop out. At idle it still drops out and each time the value of trigger signal goes down. Why is that occurring? What should the value of the trigger signal be?? Mine ranges from +18 to -2.

Many thanks to the administrators for directing me to how the trigger works. I am still not sure why a variation of a few thousands in the trigger tooth to sensor would matter that much.
How close should the trigger wheel be to the sensor and how much variation in this distance is acceptable?

The "trigger +-" signal is generally pretty difficult to interpret; I wouldn't rely on that for troubleshooting here. Do you have a data log of how it's behaving with the changes to the sensor gap?

Matt Cramer wrote:The "trigger +-" signal is generally pretty difficult to interpret; I wouldn't rely on that for troubleshooting here. Do you have a data log of how it's behaving with the changes to the sensor gap?

Here is latest log with about 0.016 max trigger gap and a variation of about 0.008 concentric.

Try adjusting the Next Pulse Tolerance settings.

Matt Cramer wrote:Try adjusting the Next Pulse Tolerance settings.

I will try that.
Should the the (2) variable resistors(for VR conditioning) on the main PCB be set at any particular place or do the have no effect on the hall sensor?

A Hall sensor is less picky about the range of adjustments, but it is still possible to adjust it to a point where it won't work.