As mentioned in some of the other posts on this forum, your problem may be due to the low oil pressure safety killing the ignition. The switch, typically built into the oil pressure sending unit, may be bad, or, the engine's hot oil pressure may be so low that the safety trips. My 1983 S-10 with the 2.8 V6 will light the low oil pressure idiot light at idle if I don't use at least 10W-40 oil in it.
Hope this helps:
Oldengineer