On final approach a MD80's left thrust lever was stuck at a mid range EPR and would not retard. An emergency was declared but a go-around was executed because of a microburst on short final. The crew proceeded to their alternate and after touchdown secured the engine before taxiing to the gate.

Narrative

Weather at our destination was 500 FT overcast with heavy rain; winds at 230/20; altimeter 29.36. At approximately 4000 FT in IMC all anti-ice on approximately 20 miles from the airport and 3 miles from ILS intercept; I the pilot flying; noticed the left throttle would not retard to less than 1.35 EPR. I directed the First Officer to declare an emergency and consult the QRH for a procedure. The APU was started. The First Officer efficiently completed all tasks. We decided to leave the engine running until landing rollout. Descending through approximately 2000 FT; the Tower reported a microburst alert with 40 KTS gain. Our airspeed increased from 150 KTS to 175 KTS. I initiated an escape maneuver go-around. Tower gave us instructions to climb runway heading to 4000 FT. I elected to divert to our nearby alternate where the weather was better. TRACON gave us vectors for ILS. I landed on and upon touchdown had the First Officer shutdown the engine with the fuel lever. Because the throttle was stuck forward; the spoilers deployed and then retracted. The First Officer then redeployed the spoilers. We taxied clear of the runway and had Airfield Rescue and Fire Fighters check us over. We then taxied to the gate.