I have a problem that needs some consultation. My very low mileage '88 cargo van (5-speed with 4Y engine) was running almost daily for the past year without incident, until a recent oil change, where the valve cover gasket was found to have a leak that required its replacement. (no prior oil leak had been detected at its parking spot)

Abruptly, the engine also began to misfire intermittantly, apparently on one cylinder, with "check engine" light on (also intermittently). After replacing the gasket, analogous symptoms persist: normal idle, but intermittant rough running, with brief (<1 sec) power drops at intermediate engine rpm's, without further warning lights so far.

Previous discussions on this site have noted a problem with rust particles forming, likely in the fuel tank, becoming dislodged, and migrating to the fuel injectors. This blocked their screens, disrupted fuel flow, and generated symptoms like those noted above.

Questions:

1) What other problems give similar symptoms?
2) How long does it take, approximately, and how much engine disassembly is requried, to clean injector screens (and replace the fuel filter)?
3) If there is rust forming in the fuel tank, does the injector problem simply reoccur regularly, till the tank is cleaned out, presumably followed by coating the tank with rust preventing polymer?

Maurice