lets start in November when the timing chain and water pump were replaced in my 1999 cavalier z24. The car ran beautifully before it went in for the work, the day it came back it started stalling, not starting again for a while, missing and shutting down while doing highway speed. The only code it threw was oxygen sensor. it wend to another shop and had fuel filter changed, car ran good for a bit then would miss and stall again but would start up right away again. Then it started revving itself up and down. Its been on many computers, none of them show anything is wrong with the car. It is feburary now and the car has not even started in 2 weeks. Computer has been changed, ignition has been changed. Fuel pump is not coming on and anti theft light is on solid. car will turn over but it is not getting any fuel and will not start.... Can not figure out what is wrong with the pos... please help.

I'm going to assume that the shop(s) that did the work haven't been any significant help (but I don't know why you wouldn't have any recourse through them). In order to replace the water pump, the HEI (ignition module) would have to be removed and it's plausible that a problem with it, the rubber spark plug boots or contact springs (created by the R&R) could cause bad running, missing, etc.. Also, the exhaust sytem would have to be disconnected and I can visualize how an oxygen sensor problem (again created by the R&R) could result. Lastly, the anti-theft system would cut the fuel as you describe, and there are several ways that could be affected while working on the other problems. There isn't anything overly mysterious about these cars that isn't similar to others by GM from the same era. There has to be some diagnostic indication of a problem and your best bet is to find someone competent at troubleshooting (rather than just replacing parts) as it seems multiple issues have been created while doing what is a labor intensive, but more or less straightforward repair.

I wonder if the crank position sensor is going and is just intermittent.This might cause it,I do not know being I am 1st gen but tracing out issues leads to some of the most simple problems sometimes.