have 1995 s320,out driving today on interstate ,50-55 mph went to pass a car and hit passing gear (auto) when car came back to normal speed notice slight stumble . made it home , thought it was a fouled plug,changed all 6 ,none looked bad. car still stumbles -low power , like timing off ? limp home mode ?? what might of caused this ,only hit moderate r.p.m.s when passing other car!! car still acts up even after restart , any ideas thanks Joe T.