Hello:
I have a 2002 Astro 4.3L 2 wheel drive. I was diving and I noticed the check engine light came on. several minutes later the truck stopped running. I had it towed to my house and when I took the engine cover off I found that one dist. cap screw was gone and the second was loose. I also found the rotor had come off destroying the inside of the cap. all parts were replaced and when started it ran. I still had the engine light. I checked the code and it said crank position sensor. I replaced the sensor and cleared the code. When it is started the engine stumbles a little and sometimes it stalls out. The engine seems to run a little slugish, weak as well. then after a cou[ple of days the code came back and when checked it shows it is the crank sensor again.
need help Vince

 

First thing I'd do is make sure the crankshaft and distributor are line up correctly. Don't have the procedure handy, but any repair manual has it in it.

Very easy to mis-align and have the spark not hit when it should.