92 Transport 3.8l Engine Shudder

[carignanr]

My 1992 Pontiac Transport has an intermittant shudder (feels like an engine mis-fire) at light loads from 30 MPH and up. Usually in a higher gear or when a slight load. The SES light was on and a code reader revealed 34. I replaced the MAF sensor and the SES light is out, but the SHUDDER remains. New spark plugs and plug wires. Sometimes no shudder for a few hours of driving. Suspect Coil Pack but reluctant to just start changing parts.

Any tests that can be done without special equipment? I have a digital ohm meter and hand tools.

[LMP]

Any mention of "shudder" usually makes the TCC a suspect...but at 30mph, it does not figure.
But that might be a signal of a low hydraulic pressure leading to transmission clutch slipping (under light loads as you say) ..or worn clutches. In any case, what is the status of transmission maintenance...any recall than the fluid has been changed with the filter in the transmission (needs removing the transmission pan under). A clogged filter may impair oil delivery hence low pressure...and a clogged filter would point to worn clutches. In any case, filter replacement would be a normal low cost maintenance item before considering anything more complicated.