I have a 04 Impala with 3.4.Sometimes when I turn the key on the coils will fire a weak spark.I don't mean start I mean run position.I also noticed a small ac waveform on my yellow wire going to the ckp sensor on block when I turn key on.anybody had this happen to them.I assume there is a short somewhere but I am scratching my head.Any feedback would be appreciated.

 

I junked the intake manifold with TBI ThrottleBodyInjection. Now its shiny-new 4barrel carb with giant chrome hat !
Hit the starter and fireworks everywhere !
Junked the HEI coil et al. New fire-engine-RED 1-piece distributor.

The fool-injection computer also controls juice and pulses to HEI ignition.

You may not have a short. Its the lack of a signal, that fires the coil.
Ever notice there are 2 power & 2 ground wires & 1 pulse wire.
Be karfull, it does sting like a bee !