Got a harmonic vibe and getting cut outs

[Rogerd]

Just installed my MJ into a rover V8 with Eddy carbs. All seemingly was mostly ok but then got misfires and eventually found the VR sensor plug had come loose. Plugged it back in. Made doubly sure it's ok.

I have a few issues:

1) I have a new harmonic vibration that starts around 1500 and goes through to 3000. Never did that before.
2) At idle, the engine momentarily cuts , every couple of seconds. Just enough for the revs to drop from 1k to around 700. The display on my laptop reflects this. On one occasion I saw the rpm drop to zero on the computer display before it receovered.
3) Occasionally while testing (stationary) the engine dies and I have to turn the ignition off and on again, or I get no spark.
4). Under even the lightest load, my engine momentarily cuts at between 1500 and 1800 rpm. Enough to lurch the car badly. It powers through the rest of the revs ok, with the odd miss.

My VR sensor is a human hair-close to the trigger wheel. Any closer and it would hit. It's mounted almost radially.

[brentp]

Hi,

it sounds like there's a change in the VR signal around certain RPMs that might be confusing the EDIS module, causing it to lose sync with the trigger wheel. This can be caused by a harmonic vibration in the sensor. The sensor bracket needs to be extremely rigid and not vibrate under any condition. Typically we see mid-range cut-outs, but it could happen any time depending on the natural harmonics of the mechanicals.

What I would do:

1) put an oscilloscope on the VR sensor leads at varying RPMs to see if the signal distorts.
2) Gusset, brace the VR sensor
3) double check the material of the trigger wheel (looks like regular carbon steel, however)
4) check wiring, shielding on cables and voltages.
http://autosportlabs.net/MJLJ_V4_vehicl ... tion_Steps

Please let us know what you find!