5.7 engine won't start unless accelerator is fully depressed, dies if you let rpms get low. If you can keep it running for a couple of minutes (2 to 3k rpm) you can get it into gear at about 1k and it drives semi-normal, then eventually it will idle in park at 1k or so.
If you shut it off, it starts the same problem all over.
The shop can't take it until Tuesday.
Background 160,000 miles and did a 180 mile highway trip without incident the day before this happened. Started normal that morning, then drove to a strip mall. After sitting for 30 minutes the trouble began.
Any ideas besides injector or pump?
The truck has been nearly trouble free for 16 years.

"Be sure you're right. Then go ahead." Fess Parker as Davy Crockett