A good afternoon

[kywes@bellsouth.net (Wes Brockway)]

Long story short. Decided to piddle around on my 87 16V roc this
afternoon (that means mess around with). Finished replacing the shift
bushings, cleaned the airbox, etc. In the process I find a sensor coming
off the back of the head just kinda underneath the distributor. The wire
was broken off. It is a single green/black wire with a spade lug that
slides on the sensor. Don't know what it is but it shure made the 'Roc
roll better.
I checked the Bentley but I guess I'm blind.

Can someone tell me what this sensor is, what it does, and so why it
improved how the car ran?