It won't run roughly with a broken timing chain, since it wouldn't run at all. It will run with a slipped timing chain, but that's not very common on SBC engines built after 1984. Further, there is no need to remove the radiator and grille to replace a timing set. And there are no gears. There is an inverted link chain and two sprockets. The only "gear" even possibly involved would be the gear cut on the back of the cam sprocket used to drive the balance shaft on later engines, and your 1990 262 doesn't have one.
The Coyote is correct. A quick way to check (and dismiss) the question of a timing chain is to bypass the EST and check base ignition timing. Once you've eliminated that, get out your fuel pressure tester and adapter to see if you have at least 11 PSIG fuel pressure.
Before you go even that far, make sure you hear the fuel pump runs its two-second prime cycle when you turn on the ignition. Without that, testing fuel pressure would be futile.
Geez! I just realized this is a resurrected thread from almost two years ago. I wonder if it ever got fixed....
