1998 4.3 bucking, cutting out intermittent

[jcronk69]

My 1998 c1500 4.3 5 speed just developed a problem tonight.
I went out to get a pizza, probably 7 or 8 miles from my house.
On the way down, i thought i felt it buck, like the motor lost for a second. It ran fine the rest of the way.
On the way back, it did it several times. It seemed to do it just about every time I shifted into 3rd gear in the city, and the rpms were 2000-2500.
It did it coming up a hill on the highway in 4th gear also.
This is a new GM engine I just installed a week and a half ago. I also installed a new fuel injection spider.

Just looking for suggestions on things to check. A mechanic friend of mine said could be a crank sensor going or a fuel pressure problem.

 

[df2x4]

Could be ignition related, I have had a bad distributor cap cause a similar issue on my 4.3 truck.

 

[RyanMerrick]

Could be a fuel delivery issue, but it seems more likely an electrical problem.

I actually had a similar issue a couple years ago, it was a loose battery cable...

 

[magimerlin]

My 94 was doing that just a big ago... I replaced yhe plugs and it all went away.. my old plugs looked terrible....lol

 

[jcronk69]

The distributor was replaced during the engine replacement with an aftermarket aluminum distributor to replace the trouble prone plastic one.
It came with a cap and rotor. I also replaced the plug wires and installed new AC Delco iridium plugs (oem installed plug).
I drove to work and back today and it ran fine. I'm stumped!