NEWLY DESIGNED SERVICE MANUAL FOR CCC ENGINE SYSTEMS

MODELS AFFECTED: ALL 1984 COMPUTER CONTROLLED CARBURETED AND FUEL INJECTED VEHICLES

SECTION 6E "DRIVEABILITY AND EMISSIONS" INFORMATION HAS BEEN COMPLETELY REVISED FOR 1984. THE NEW FEATURES OUTLINED BELOW WILL ASSIST TECHNICIANS TO DIAGNOSE PROBLEMS MORE EASILY, SAVE TIME AND INCREASE CUSTOMER SATISFACTION.

COMPONENT AND WIRING HARNESS LOCATOR VIEWS

The "INTRODUCTION" section contains computer controlled engine system harness and component locator views.

. ECM TERMINAL DATA AND VOLTAGE CHECKS -------------------------------------- Also included in the "INTRODUCTION" section are specific computer controlled engine system circuit schematics and terminal connection information. This information provides voltages with the ignition "ON" and engine not running. Also provided are voltages for Closed Loop Operation.

. SUPPORTIVE INFORMATION ON PAGE FACING TREE CHART -------------------------------------------------- Section A contains the diagnostic code display procedure called the "Diagnostic Circuit Check" and the diagnostic codes tree charts. These charts provide an easy-to-follow troubleshooting path (see pg. 3). The diagnostic charts have a facing page which includes a wiring diagram of the circuit involved, brief description of operation of that specific circuit, and explanation of the purpose of significant steps in the chart.

. SYMPTOM DIAGNOSIS RELATED TO SPECIFIC FUEL CONTROL SYSTEM ----------------------------------------------------------- Section B contains driveability symptoms diagnosis procedures which are specific to each engine fuel system.

SECTION B - SYMPTOMS 3.8L ------------------------- Intermittent 'SERVICE ENGINE SOON' Light...................6E3-147 Hard Start....................6E3-148 Stall After Start ............6E3-148 Hesitation, Sag, Stumble .....6E3-148 Surges And/Or Chuggle.........6E3-149 Lack of Power, Sluggish, or Spongy........................6E3-149

Detonation/Spark Knock........6E3-150 Cuts Out, Misses..............6E3-150 Backfire......................6E3-151 Poor Fuel Economy.............6E3-151 Rough, Unstable, or Incorrect Idle,

Stalling......................6E3-151 Won't Idle....................6E3-152 Dieseling, Run On.............6E3-152 Excessive Exhaust Emissions (Odors).......................6E3-152

SURGES AND/OR CHUGGLE

Definition: Engine power variation under steady throttle or cruise. Feels like the car speeds up and slows down with no change in the accelerator pedal.

. Be sure driver understands Transmission Converter Clutch and A/C compressor operation in Owner's Manual.

. Check air cleaner damper door (THERMAC) operation (see (THERMAC Section).

. Perform careful visual inspection as described at start of Section B.

. If a tool is available which plugs into the ALCL connector, make sure reading of VSS matches vehicle speedometer. See "Special Information" at the end of this section.

. Check for proper operation of EGR. See CHART C-7, (Figure 122)

. Check for proper operation of ESC. See CHART C-5, (Figure 103).

. Check ignition timing. See Emission Control Information label.

. Check in-line fuel filter. Replace if dirty or plugged.

. Check fuel supply system for water in tank and proper pressure. Should be 62 - 90 kPa (9-13 psi) in all speed ranges.

. Remove spark plugd. Check for cracks, wear, improper gap, burned electrodes, or heavy deposits. Also check conditions of distributor cap, rotor, and spark plug wires.

. Check valve timing, see Section 6A.

. Inspect Oxygen sensor for silicone contamination from fuel, or use of improper RTV sealant. The sensor may have a white, powdery coating and result in a high but false signal voltage (rich exhaust indication). The ECM will then reduce the amount of fuel delivered to the engine, causing a driveability probem.

OPERATION AND SERVICING INFORMATION

Section C describes the basic operation of individual systems which are part of the computer controlled engine performance package. This section includes on-car service and diagnostic charts for each system along with carburetor calibration, idle speed control adjustment, mixture control solenoid and injector R&R, etc.

Service Parts Catalog names and group numbers are also provided with the on-car service information.

We feel the expanded format of Section 6E will help you, the technician, more effectively diagnose and repair computer controlled fuel systems.

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.