Interrobang

Sounds exactly like how my '77 was misbehaving. Turned out to be the water temperature sensor (or at least replacing that fixed it). Cost $15, got it from Amazon.com, believe it or not. Off the top of my head, I remember that L-Jetronic senses Air flow, air temp, water temp, and ignition pulse. Air temp and air flow readings come from the AFM, water temp sensor is in the themostat housing, and ignition pulse is read off of the coil (or maybe the distributor, I don't remember). If you have verified that you have good fuel pressure as well as spark on all cylinders, start checking your sensors. AFM/air temp is the expensive one, but you might find a used example in the classifieds here.