A B737-800 Captain described an approach to CYYZ in icing condition with an engine high pressure bleed blocked closed. To allowing anti-ing 60% N1 was required which made the IMC approach challenging because speed control was a problem.

Narrative

The days sequence began with airplane write up; 'Left engine hi stage air inop -- valve locked closed.' We had brought the same aircraft in the night before and were hoping the hi-stage valve would get fixed but it didn't happen. MEL stated that in icing conditions the power must be kept at 60% N1 to keep engine and/or wing heat operative. The first leg was uneventful. At predeparture weather for CYYZ was something like 7 degrees overcast. We took the plane not worried about icing conditions and the engine write-up. Fast forward -- approaching CYYZ; approach changed the landing runway from 24R to 05 as we were descending through 20;000 FT. We were on the WATERLOO 2 Arrival and were given clearance to cross ROKTO at 7;000 FT and the aircraft began to ice up. Engine and wing heat were applied. Throttles had to be kept at 60% N1 per MEL. Even with the speed brake fully extended throughout the descent there was no way we were going to make the ROKTO restriction and I told the Controller as much. 'No problem;' we took a turn to the northwest to allow room to descend but it was still a struggle to keep the power up and descend and slow especially at 10;000 FT. Still in icing conditions -- I would call it light to moderate rime. Continued the descent to the field; still in icing conditions and power is still at 60% for deicing. Cleared for the approach to Runway 05 at about 4;000 FT began configuring very early to help slow the airplane with power on for continued icing-speed brakes still out. Very close to flap overspeed limits; but we did not overspeed. Speed brake being manipulated to keep the aircraft slowing with throttles still up for icing. Two dots above the glideslope at about 2;500 FT the Controller asks if we were going to be able to get down. We answered yes; we'd like to continue. Started to break out at about 1;500 FT throttles immediately pulled back by pilot flying (First Officer) and we were pretty close to being stabilized and on glideslope at 1;000 FT VMC and stabilized at 500 FT. Landing was uneventful. With 20/20 hindsight; I would not have accepted the aircraft for the CYYZ leg. Lesson learned -- look at weather and aircraft MEL limitations closely -- if in doubt don't accept the aircraft until it gets fixed! Nice airmanship by First Officer into the field under less than ideal circumstances.