Microsecond misfire at hiway speed

[Srg1016]

Looking through most of the “miss” post here I’m not seeing my exact problem. My new to me 98 k1500 is in great condition for its age other than my problematic miss. Heres the problem:
At freeway speed say 70 the engine will have a quick “ millisecond” misfire. It happens 2 or three times in say 15 to 25 miles. Sometime the miss is almost what I would call violent, as if the ignition was turned off for less than a second.Whats been done:
Engine 7000 on the clock, replaces by prior owner at 129 k due to mechanical failure.
Distributer changed as we’re all sensors.
I do not have a scanner and have no idea who could help me here in Yuma Arizona.
Anyone have any thoughts or know any qualified mechanic in Yuma who might help me?
Thanks in advance

 

[Schurkey]

Verify fuel pressure at prime, and under load.

Verify all the usual "tune-up" items. Distributor caps are infamous for failure on Vortec engines, as is the distributor gear and the plastic distributor body. Rotor, plug wires, spark plugs. Check PCV and EGR systems. O2 sensors get lazy with age, if you don't know their service history, they're ripe for replacement.

Assure no vacuum leaks, including to the MAP sensor. Any vacuum leak will disturb the air-fuel ratio which then MIGHT be compensated for by the O2 sensor...if the O2 sensor is working properly.

You clearly need a scan tool. There's some short-cuts that can sort-of be performed with a multimeter. The multimeter takes ten-plus times as long for less-accurate results.

ALL the ignition-system wiring harness from battery to ignition module and coil needs to be checked for damaged connectors, burnt connector terminals, loose pins, and any other cause that could interrupt power to the module/coil.

 

[Srg1016]

Schurkey thank you for your response. I think most of my problem figuring this out is I have no scan tool and probably wouldn’t know how to use it. Regretfully I have no choice to throw parts at it as in: New 02 sensors,
new distributer, new coil, new TPS, new plugs, wires and cap while carefully routing the wires and new CPS. A friend of mine visiting brought an older scanner and was able to set the cam retard at “0”. Problem is it was his “old” scanner and because of the lag in real time he was not able to read the misfire in real time. His new scanner is getting the latest update n the shop and unfortunately he has left back to Idaho. I do know how to use a multi meter and I guess I’ll start running down wires as you suggested. I really appreciate your response and thank you again. If I get it figured out I’ll be sure to post here with the hope it will help others.
If anyone reading this knows a good shop near Yuma Az please let me know?