GF's 99 Yukon has been developing a no start issue.

Motor comes to an abrupt halt, shudder and shunts when cranking. Sometimes complete stops then continues cranking.

Took off cap and rotor, both were dirty; cleaned points with a Dremel wire wheel. Fired right up multiple times, told girl she can drive the truck to work the following day. Comes back in in the morning and wakes to tell me it's once again doing the same thing. Then will run again, then wont, then......

Fuel pressure good, new CPS, terminals tight and clean. Changed over complete throttle body and coil/ICM from my Tahoe; same result and Tahoe has been running great for days.

Does not seem starter or short related. Itll either fire right up, or turn and turn then kick back, or turn and immediate kick back. Never just turns, turns, then starts. Pretty much can immediately tell if it will run or not. When it runs, it runs perfectly!

Turns out the spark plug tester was a waste; tons of wasted attempts (with it not running). So just decided to grab another plug and use jumper cables. Sparked without issue. And I just knew it would leave me on a hanger so I immediately decided to hook the wire back up and sure enough it fired right up! AHHHHHHH!

Cranked instantly next 10 times and runs perfectly... fkn figures. So now I have no idea if it was a valid test.

Lets assume its an intermittent no spark on start; what would cause this?`

Videos:
Start and shudder start;
https://www.youtube.com/watch?v=eRNb...ature=youtu.be

No start, and putter; with fuel pressure;
https://www.youtube.com/watch?v=W7XK...ature=youtu.be