The Allante was once again available as a convertible or as a convertible hardtop that included both a convertible top and a removable all-aluminum hardtop.

The engine (cast iron cylinders in aluminum) was the same 4.5 liter V8 and F-7 four-speed automatic transaxle that was used in 1990. However, the engine had a new air intake resonator for quieter performance. The resonator remove a little bit of the roar when driving up a hill, but the exhaust note was the same as in 1990. Engine power was improved through the use of straighter intake ports and larger valves (45mm intake and 38mm exhaust). The exhaust was evacuated through thin-wall, cast iron manifolds that were shaped for minimum flow resistance. Also, to help reduce oil aeration, a new gear-rotor-type oil pump was added to the engine.

Final drive ratio was 3.21:1. The Allante's chassis was also upgraded with the second-generation speed-dependent damping system added as standard equipment. With this system, damping-select time was reduced for faster response to road inputs and vehicle speed changes. It also offered enhanced lift and dive control as well as improved diagnostics. Allante continued to offer the Bosch III antilock braking system and traction control as standard equipment. The traction control system was refined for 1991 with the addition of rubber isolated plungers that reduced noise when the system was engaged. Allante's variable-assist rack-and-pinion power steering system was also improved with a revised pump and adapter that resulted in quieter operation and enhanced reliability.

The convertible featured an improved, Phase II ergonomically-designed, power-fastening, folding soft top.

Inside, the Allante's previous light charcoal interior carpeting and floor mats were replaced with dark charcoal counterparts.