Erratic tach probe 2.2 12-1 distributor

[savagerocco]

I have an ms1 extra on an 89 ford probe. Has a 2.2l turbo. We modified the stock distributor to a 12-1 wheel, ie we took two teeth, each oposite of each other and left 11 teeth in between. I get a good pattern on the oscilloscope off the vr sensors and looking at the pattern on Tsel i am getting a clean patter, but rpm is all over the place and not stable at all. When looking at the tooth logger, I am not getting a even pattern. I am getting double tall lines and from short to medium on the 11 between the tall lines. I have adjusted the voltage and hysteresis pots untill I no longer get a patter at Tsel, but something is just odd.

I have a signal interceptor board that I am pulling the vr signal from that and have a test point on the Tsel for the conditioner output. everything looks fine untill it hits the processor and it just doesn't like it. This was previously a running car, owner changed the distributor and got the air gap too far apart. I adjusted that and get a really clean waveform on the VR and polarity looks fine. Any ideas?

[Matt Cramer]

Also, please attach the problem tooth logs.

[savagerocco]

I guess I am going to have to wrap my head around the VR setup. I thought for sure I had the polarity correct, but just to make sure I crossed them and all of the sudden the double tall lines went away. I cranked the pots all the way counter clockwise and I have a nice looking tooth pattern and a stable cranking rpm of about 200 rpm. Not really sure yet if there are any more gremlins causing issues, but I should have it running soon and will update.