The LD2 was the standard version of the Quad 4, and the first incarnation was introduced in 1987 for the 1988 model year.
In base form, the Quad 4 put out 150 bhp (112 kW) from 1988 to 1989 and 160 bhp (119 kW) from 1990 to 1992.
GM was able to produce the 160 bhp (119 kW) with neither a turbo, nor an EGR system to pass emission standards; it required a 9.5:1 compression ratio.
The base Quad 4 saw several slight changes during its production run including different crankshafts, cams, and manifolds, all meant to increase torque and lessen the NVH.
In an effort to yield 5 additional HP some highly opted 1992 RPO LD2 SC Oldsmobile Achievas received a vortex valve along the TB induction pipe runner with an injection molded auxiliary induction tube funneling cool air from outside the engine compartment to the airbox via the openings around drivers side headlight (ram/air replete with cold weather block off plate in radiator core support) as until the engine warmed up would cause stumbling issues with the MAF sensor.
There was also a transitional version of the LD2 in 1995, which displaced the same 2.3 litres (2,260.5 cc) as the early Quad 4 but featured the dual balance shafts of the later quipped 2.4 L (2,392.3 cc) LD9 Twin Cam.

Applications:
1988–1991 Buick Skylark
1992–1994 Oldsmobile Achieva
1988–1991 Oldsmobile Cutlass Calais
1990–1991 Oldsmobile Cutlass Supreme
1988–1994 Pontiac Grand Am
1990–1991 Pontiac Grand Prix
1993–1997 Pontiac Trans Sport (Europe only)
The LD2 was the standard version of the Quad 4, and the first incarnation was introduced in 1987 for the 1988 model year. In base form, the Quad 4 put out 150 bhp (112 kW) from 1988 to 1989 and 160 bhp (119 kW) from 1990 to 1992. GM was able to produce the 160 bhp (119 kW) with neither a turbo, nor an EGR system to pass emission standards; it required a 9.5:1 compression ratio. The base Quad 4 saw several slight changes during its production run including different crankshafts, cams, and manifolds, all meant to increase torque and lessen the NVH. In an effort to yield 5 additional HP some highly opted 1992 RPO LD2 SC Oldsmobile Achievas received a vortex valve along the TB induction pipe runner with an injection molded auxiliary induction tube funneling cool air from outside the engine compartment to the airbox via the openings around drivers side headlight (ram/air replete with cold weather block off plate in radiator core support) as until the engine warmed up would cause stumbling issues with the MAF sensor. There was also a transitional version of the LD2 in 1995, which displaced the same 2.3 litres (2,260.5 cc) as the early Quad 4 but featured the dual balance shafts of the later quipped 2.4 L (2,392.3 cc) LD9 Twin Cam.
Applications:
1988–1991 Buick Skylark
1992–1994 Oldsmobile Achieva
1988–1991 Oldsmobile Cutlass Calais
1990–1991 Oldsmobile Cutlass Supreme
1988–1994 Pontiac Grand Am
1990–1991 Pontiac Grand Prix
1993–1997 Pontiac Trans Sport (Europe only)
Quad 4 engine