GM Quad-4 Engine - LD9

LD9

The LD9 Twin Cam was a 2.4 L (146 cu in) Quad 4 variant with balance shafts, and a redesigned cylinder head which debuted in 1996. In the mid nineties, these engines, like their earlier 2.3L counterparts, were known for timing chain failures, as well as water pump failures, in which the water pumps were often difficult and costly to access and replace. They also had very small oil passages, making for less than adequate lubrication, and costly engine repairs if not maintained properly. Bore was decreased from 92 mm (3.6 in) to 90 mm (3.5 in) and stroke increased from 85 mm (3.3 in) to 94 mm (3.7 in) for better torque. Power came in at 150 bhp (110 kW). This engine received a minor update halfway through the 1999 model year that eliminated the EGR, increased the compression ratio from 9.5:1 to 9.7:1, and switched from low impedance fuel injectors to high impedance. For increased reliability, this engine also saw other minor updates in the 2000s, towards the end of its use in General Motors vehicles, such as a smaller knock sensor, flat-top pistons instead of dished, new oiling passages, newer stronger timing chain, a newer-designed water pump, a redesigned starter motor and higher capacity catalytic converter in 2001, and an improved belt tensioner in 2002.