For 1990-2009 cars

# IGNITION AND FUEL SYSTEM DESCRIPTIONS

#### VEHICLES AFFECTED: 1988 AND 1989 DIFFERENCES - N SERIES

1988 and 1989 ignition modules on a 2.3L Quad 4 engine are not interchangeable.

In 1989, a 15 degree advance crankshaft is used on a 2.3L vs. a 0 DEG advance crankshaft on 1988 2.3L engine. This required different module timing to be compatible with the intial timing advance of the crankshaft reluctor wheel. The timing advance enhances cold startability and emission.

A 1X reference signal was also added in 1989 for better fuel control and emissions. This signal is used to fire the paired injectors in the correct sequence. This is called ASDF Fuel Injection which is described in section 6E3-C2 of the 1989 service manual.

Two different methods of fuel injection are used on the Quad 4 engine.

In 1988, all 4 injectors are pulsed simultaneously, delivering half the necessary fuel for combustion at each revolution.

In 1989, a pair of injectors are fired every 180 degrees of rotation. Injectors 1, 4 and 2, 3 are paired and pulsed twice, once on compression and once on exhaust stroke for each cylinder.

General Motors bulletins are intended for use by professional technicians, not a "do-it-yourselfer". They are written to inform those technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions and know-how to do a job properly and safely. If a condition is described, do not assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See a General Motors dealer servicing your brand of General Motors vehicle for information on whether your vehicle may benefit from the information.