Hacker, it's telling the ignition system to fire the coil. Also, the tach signal keeps the fuel pump energized, and on 78/79 it tells the AC speed relay that it's OK to engage the AC clutch -- clutch stays disengaged while cranking.

 

As Dave points out it can really mess with how and when the 78-84 cars run ... The 911 uses a similar Green Wire 1970s-80s and one well reguard shop will NOT start tuning troubleshooting those until it gets a new green wire. Spend hours chasing your tail or spend $106 for a $10 piece of wire that is KNOWN to be a common failure item causing all kinds of intermittent timing and performance problems. The post is an FYI it has been a long time since the subject was discussed and there have been a lot of people picking up older cars...besides I need the money

 

So the sensor in the distributor that sends the signal down the green wire - does it send one "blip" per revolution or one per cylinder?

 

One per cylinder, 8 per cam revolution.

 

It takes the place of the contact points that used to be inside a distributor. Which makes this a pointless ignition system .....Much has been written since 1879 when Mr Hall discovered the Hall Effect a 127 years is a long time ! It generates a very clean square wave signal a nearly perfect on off "switch"......

 

Jim,

Would the Green wire cause an intermittant problem that can be cured by turning the car off and on?
My car started to loose power on our 3rd Coast tour. It started to almost feel like the car was cutting out intermittantly, then slowly but surely, the power kept dropping and dropping until finally when I would give it a little gas, the car would almost die. I turned the car of, then turned the car back on and it ran ok. I got the car back to Dallas (220 miles) by doing this about every 10 minutes or so. I've change the TZK and the coil with spares but it did not change a thing. I'm thinking from what you're describing, it may be the Green Wire. Thoughts?