DIESEL EXCESSIVE BLACK EXHAUST LOSS OF POWER

MODELS AFFECTED: Some 1983 Centurys Equipped With A V-6 Diesel Engine

Some 1983 Centurys equipped with a V-6 diesel engine may experience a condition resulting in excessive black exhaust smoke and no power. An inoperative vacuum regulator valve, which allows full time EGR and EPR, could be the cause of such a condition. To test the vacuum regulator valve, install a vacuum gage at the vacuum outlet port of the V.R.V. leaving the vacuum source connected at the inlet port. With the engine running, note the vacuum readings while changing the throttle angle. The vacuum readings on a good vacuum regulator valve should raise and drop with changes in the throttle angle.

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.