A preliminary injunction forbidding the Rev. Ian Mitchell to perform any functions as rector of St. Athanasius Episcopal Church in Echo Park after Nov. 20 was issued by Superior Court Judge John L. Cole, who said he will appoint a retired jurist to try to mediate. But lawyers for both sides said an out-of-court settlement is very unlikely. Episcopal Bishop Robert Rusak had asked for the order, on the ground that Mitchell's election as rector of the city's oldest Protestant congregation was illegal, since the priest's license to preach and celebrate Mass had been revoked. Mitchell's supporters responded that he was being forced out because he attracted Latinos and homosexuals as new members of the congregation. In recent months, the issue has so divided the parish that rival Sunday services have been held in the main sanctuary and parish hall.