OT But Need Help...

Would show up on an ignition scope.

Low amps probe on a lab scope.

Pressure gauge or transducer.

Low amps probe on a lab scope, a visual inspection for carbon tracking on the towers and stress testing with a ST-125 spark tester.

You mean ignition module? Primary ignition scope, low amps probe on a lab scope, test light across the primary leads to the coil.

Systematic testing. If the injector was plugged, the lean air fuel ratio tends to put a lot of stress on the ignition system. If the injector was shorted, it could have damaged the injector driver in the ECM. You could have also gotten a bad injector, were they new or reconditioned? What's the fuel pressure? What do the spark plugs look like? (color and visual check for carbon tracks or center porcelain dropping down over the gap) What is the resistance of the ignition coils (primary and secondary)? What is the resistance of the spark plug wires? Scan for fuel trim numbers.

Everything has to be done on a budget and without an extensively large tool supply. No scope, no specific testers...just a 1 car garage, years of mechanic ability, and a quest to do what is needed without spending money fixing things that aren't broke.

In reference to the coil plate. It is what the 3 coils bolt to. I have had them act up before but only when warmed up...just not with this level of shutter.

I am leaning towards trans shutter...but a flush and filter should have at least changed the shutter, right?

I can't imagine how this could be accomplished without at least

-some- test equipment. A DVOM and an ST-125 spark tester (two for DIS) probably wouldn't set you back more than $40.00

That would be the ignition module. Often times, the module ground path becomes corroded and weird things, temperature related things happen. The ultimate ground path for the ignition coil primary is thru the base of the module, thru the bracket that it's bolted to to chassis/engine ground. Old/dried out heat sink grease causes problems also by not allowing heat to dissipate thru the base of the module into the mount, the ignition module runs too hat and either doesn't work correctly or fails totally. Cheap easy things to try.

Maybe... ... often times it takes driving the vehicle a few hundred miles before the torque convertor clutch beds in with the new fluid and the shudder goes away totally, although i see this more frequently on Fords than GMs.

I was told by the owner of the car that it had the shutter before the flush just like it does now. Coil plate...Ignition Module...either way...LOL

I am gonna check a few things tomorrow morning.