Not sure if this is MSD or PCM related, going to switch coils in the morning...on the MSD right now.

My truck is randomly cutting out at speed. It started as just completely shutting off for a second or so, coasting, then coming back up, staying in the same gear. Now it's going in and out of O/D, stumbling, tach needle jumping between 300 and 4000 (even though i know the motor isnt getting near that high), lope-ing, all kinds of goofy stuff. But it'll do it, be fine for a few days, then do it again. Completely inconsistent. On the way home, going 65, it would stumble, lope, go into 3rd, stumble, almost die, come back to life, then hang out in 3rd before going back to OD.

I just did a plug change and the ones that came out where solid white on the electrode and gapped 60-65. I put new 3923's in gapped at 40. When I lift, my (4) O2 voltages all go to 0.000 on the ultragage, under throttle they're around 0.780-0.880 volts. May not mean much on the narrowbands, but still something.

I may go hunt down the fuel pressure gauge before I leave. Wish the hose was longer so I could watch it while driving.

 

No change at all running on the PCM. Checked all the plug wires, they aren't burned or seem to be arcing or anything.

 

The bouncing tach is an odd one. No codes for a crank position sensor?

MAP sensor can cause weird running and may not toss a code.

 

Just the usual 0442 code hanging out in the pending box, no active codes.

I wish the fuel hose for the gauge was long enough to reach out the hood...granted having a real fitting instead of a schrader valve right over the exhaust would be awesome too. Only takes air, fuel and spark to make an engine run...cutting out like it is, it's not just one cylinder, it's something shutting off all the way. Throttle is open so it's not the IAC, either fuel pump/injectors is shutting off or the ignition signal is shutting off.

But the tach going bonkers puts me on the same page as you, CKP acting up.