I have a '76 911S, runs perfectly and smoothly almost all the time, but
suddenly the tach goes wild, spinning from 0 rpm to 8K (engine does not
spin wildly, just the tach!), then, engine coughs, sputters, and sometimes
backfires explosively.  Yesterday I was driving past a lady on the
sidewalk, it backfired and she screamed, jumped up and was looking all
over for where she had been shot!  Sounds funny, but it is getting
embarrassing!.  It can go for weeks, just fine, then without warning, can
be soon after starting in a.m., or after fully warmed up, while
acceleratnig, or often while cruising on the highway.  I have checked for
shorting wires, replaced the dist cap & rotor; can't seem to figure this
out.

Please help before more people think they have been the target of an
assassin's rifle!  Or worse yet, they shoot back, I couldn't stand a
scratch on this car!

Thanks,

Chuck
happycamper39373@cs.com