Hi. Thanks again for the help so far.

Ok so the next problem in my project. How to sense the RPM using the pulses, obtained from a piece of copper around a plug wire, Soldered to a wire that goes to ????.

Has anyone done this or know a simple way? When I've tried the comparator or Count functions I get very poor results due to the high noise levels. I can reduce the noise down to what would seem to be acceptable, but also reduces the voltage of the signal. If use the comparator the range is to small it seems. The secondary plug fires cause a pulse of about 2.3-2.5v, with primary plug fires causing a Pulse of 2.5-2.9v. Currently the best signal I can obtain is using a 15kR, in line with the signal, then a 1k to ground, followed by a 4.9v 1/4 watt zener Diode. That is where I am getting the above voltages. The issue lies in that both coils sit right next to each other, and Routing of the spark plug wires, are in line. I am trying to pick it up, as Close as I can to the plug its self as to cut down on the other plug firing.

I tired various Schmitt triggers and Op Amps to little success. Maybe Im doing it wrong? But The pulse is so short it does not appear to need "Squaring."

Then the second question if you have any ideas, Would it be best to use the count command, and calculate RPM from there? Or The PULSIN and Measure the time of the low pulse. (I get nothing with this the signal has to much low level noise to be Logic 0, I think.)

I am using a 16F690. So I do at least have a few more options.

Any ideas would be greatly appreciated.