nook
+1y
The diagnostic plug on your 93 should be next to the fuse block under the hood on the passenger side, small little flip top box that has diagnostic printed on top, it just needs a jumper wire connected to the 2 terminals to apparently bypass the computer to set the timing, then the timing is set the conventional way with a timing light.
You could adjust the timing by ear, wouldn't have any idea where it actually was, so you would need to be cautious of the engine running hotter, pinging, detonating, so you could fine tune it as it may be too far advanced, or retarded using that method.