4k-DOA on side of road

[SHOWMX at aol.com]

Looking for a little advise on this one, after leaving my 4k on the side of 
road tonight after repeated attempts at resuscitation.  Please note, this is 
a '87 4k 4 cyl-w/CIS-E

symptoms:  car was driving fine, has been for the 50k maintained miles I've 
had it for!  Suddenly the tach completely dropped off to 0 rpm while waiting 
at a light and idling, yet the car wanted to stall but I could keep it 
running as I revved it.  While keeping it alive around 3000 rpm,  the tach 
stayed pinned at 0 rpm, bizzarre....  If I were to release the gas pedal it 
would die.  Couldn't keep it going w/red lights and all, and it soon stalled 
entirely.  This all happened in a matter of 3 minutes, or 1/2 mile  or so of 
driving....  Wouldn't restart, after 10 minutes or so it starts right up!  I 
drive another 1 mile or 5 minutes this time, and same sequence of events 
occur.  I could drive and work hard at keeping the motor running yet the tach 
was pinned at 0 rpm. This time no restart again. Battery & starter doin their 
jobs ok.


What I did:   replaced condensor w/spare (had one at the house), put new 
distributor cap on (the other was pretty ugly upon inspection & I was near an 
autoparts store).
Pulled spark plug closest to cam sprocket and confirmed spark.  Definitely 
getting fuel as the scent was obvious.  Got spark & fuel, Why no fire?

What gives?  Is this a Hall sender control unit or knock sensor control unit 
problem?

thanks for all and any replies,

B. Parenteau
Quincy, MA

'87 4kcs
'90 200 turbo