SERVICE INFORMATION OMITTED FROM SECT. 6E2 OF SHOP MANUAL

BECAUSE OF A PRINTING ERROR, SOME SERVICE INFORMATION WAS OMITTED FROM THE "FUEL CONTROL" AND "ELECTRONIC SPARK CONTROL" PORTION OF SECTION 6E2 OF SUBJECT SHOP MANUAL. THE FOLLOWING CHART WILL ASSIST YOU IN UPDATING THIS SECTION OF THE LOOSE LEAF SHOP MANUAL. WHERE IT SHOULD BE PAGES THAT SHOULD BE SERVICE NEWS PLACED IN MANUAL REMOVED FROM FIGURE NO. (NEW PAGE NUMBER) MANUAL FIGURE A 6E2-70A 6E2-73 FIGURE B 6E2-70B 6E2-74 FIGURE C 6E2-78A 6E2-75 FIGURE D 6E2-78B 6E2-76

ENGINES AFFECTED:

2.5L RPO LN8 VIN CODE: E

DRIVEABILITY AND EMISSIONS - FUEL INJECTION (TBI) 6E2-70A FUEL CUTOFF MODE NO FUEL IS DELIVERED BY THE INJECTORS WHEN THE IGNITION IS OFF. THIS PREVENTS DIESELING. ALSO, FUEL IS NOT DELIVERED IF NO REFERENCE PULSES ARE SEEN FROM THE DISTRIBUTOR, WHICH MEANS THE ENGINE IS NOT RUNNING. THIS PREVENTS FLOODING FUEL CONTROL SYSTEM COMPONENTS THE FUEL CONTROL SYSTEM IS MADE UP OF THE FOLLOWING PARTS: - THROTTLE BODY INJECTION (TBI) UNIT - FUEL INJECTOR - FUEL PRESSURE REGULATOR - IDLE AIR CONTROL (IAC) VALVE - FUEL PUMP - FUEL PUMP RELAY BASIC SYSTEM OPERATION THE FUEL CONTROL SYSTEM (FIGURE 69) STARTS WITH THE FUEL IN THE FUEL TANK. AN ELECTRIC FUEL PUMP (7), LOCATED IN THE FUEL TANK WITH THE GAGE SENDING UNIT, PUMPS FUEL TO THE TBI (5) THRU THE FUEL SUPPLY LINE (8), THEN THRU AN IN-LINE FUEL FILTER (9). THE PUMP IS DESIGNED TO PROVIDE PRESSURIZED FUEL AT ABOUT 125 KPA (18 PSI). A PRESSURE REGULATOR IN THE TBI KEEPS FUEL AVAILABLE TO THE INJECTOR AT A CONSTANT PRESSURE BETWEEN 62 AND 90 KPA (9 AND 13 PSI). UNUSED FUEL IS RETURNED TO THE FUEL TANK BY A SEPARATE LINE (10). FOR FURTHER INFORMATION ON THE FUEL TANK, IN-LINE FILTER, AND FUEL LINES, SEE SECTION 6C. THE INJECTOR, LOCATED IN THE TBI, IS CONTROLLED BY THE ECM. IT DELIVERS FUEL IN ONE OF SEVERAL MODES, AS DESCRIBED ABOVE. IN ORDER TO PROPERLY CONTROL THE FUEL SUPPLY, THE FUEL PUMP IS OPERATED BY THE ECM THRU THE FUEL PUMP RELAY AND OIL PRESSURE SWITCH (SEE FUEL PUMP ELECTRICAL CIRCUIT). THROTTLE BODY INJECTION (TBI) UNIT THE BASIC TBI UNIT (SHOWN IN FIGURE 70) IS MADE UP OF TWO MAJOR CASTING ASSEMBLIES: 1. A THROTTLE BODY (11) WITH: - AN IDLE AIR CONTROL (IAC) VALVE (14) TO CONTROL AIR FLOW, AND - A THROTTLE POSITION SENSOR (15). 2. A FUEL BODY (12) WITH: - A FUEL METER COVER WITH BUILT IN PRESSURE REGULATOR (13). - A FUEL INJECTOR (16) TO SUPPLY FUEL TO THE ENGINE. THE THROTTLE BODY PORTION OF THE TBI UNIT MAY CONTAIN PORTS LOCATED AT, ABOVE, OR BELOW THE THROTTLE VALVE. THESE PORTS GENERATE THE VACUUM SIGNALS FOR THE EGR VALVE, MAP SENSOR, AND THE CANISTER PURGE SYSTEM (SEE FIGURE 71). FUEL INJECTOR THE FUEL INJECTOR IS A SOLENOID OPERATED DEVICE CONTROLLED BY THE ECM (SEE FIGURE 72). THE ECM TURNS ON THE SOLENOID, WHICH LIFTS A NORMALLY CLOSED BALL VALVE OFF A SEAT. THE FUEL, UNDER PRESSURE, IS INJECTED IN A CONICAL SPRAY PATTERN AT THE WALLS OF THE THROTTLE BODY BORE ABOVE THE THROTTLE VALVE. THE FUEL WHICH IS NOT USED BY THE INJECTOR PASSES THROUGH THE PRESSURE REGULATOR BEFORE BEING RETURNED TO THE FUEL TANK. PRESSURE REGULATOR THE PRESSURE REGULATOR (SEE FIGURE 72) IS A DIAPHRAGM-OPERATED RELIEF VALVE WITH INJECTOR PRESSURE ON ONE SIDE AND AIR CLEANER PRESSURE ON THE OTHER. THE FUNCTION OF THE REGULATOR IS TO MAINTAIN A CONSTANT PRESSURE AT THE INJECTOR AT ALL TIMES, BY CONTROLLING THE FLOW IN THE RETURN LINE (I.E., A CALIBRATED BYPASS).

6E2-70B DRIVEABILITY AND EMISSIONS - FUEL INJECTION (TBI) ELECTRONIC SPARK TIMING (EST) SYSTEM GENERAL DESCRIPTION PURPOSE THE HIGH ENERGY IGNITION (HEI) SYSTEM CONTROLS FUEL COMBUSTION BY PROVIDING A SPARK TO IGNITE THE COMPRESSED AIR/FUEL MIXTURE AT THE CORRECT TIME. TO PROVIDE IMPROVED ENGINE PERFORMANCE, FUEL ECONOMY, AND CONTROL OF EXHAUST EMISSIONS, THE ECM CONTROLS DISTRIBUTOR SPARK ADVANCE (TIMING) WITH THE ELECTRONIC SPARK TIMING (EST) SYSTEM. ONLY THE ELECTRONIC SPARK TIMING (EST) SYSTEM WILL BE DESCRIBED HERE. ADDITIONAL INFORMATION ON THE HEI SYSTEM IS FOUND IN SECTION 6D. OPERATION THE STANDARD HIGH ENERGY IGNITION (HEI) SYSTEM (DESCRIBED IN SECTION 6D) HAS MODIFIED DISTRIBUTOR MODULE WHICH IS USED IN CONNECTION WITH EST. THE MODULE HAS SEVEN TERMINALS INSTEAD OF THE FOUR USED WITHOUT EST. TWO DIFFERENT TERMINAL ARRANGEMENTS ARE USED DEPENDING ON THE DISTRIBUTOR. TO PROPERLY CONTROL IGNITION/COMBUSITION TIMING THE ECM NEEDS TO KNOW: - CRANKSHAFT POSITION - ENGINE SPEED (RPM) - ENGINE LOAD (MANIFOLD PRESSURE OR VACUUM) - ATMOSPHERIC (BAROMETRIC) PRESSURE - ENGINE TEMPERATURE THE EST SYSTEM CONSISTS OF THE DISTRIBUTOR MODULE, ECM, AND CONNECTING WIRES. THE DISTRIBUTOR HAS FOUR WIRES FROM THE HEI MODULE CONNECTED TO A FOUR TERMINAL CONNECTOR WHICH MATES WITH A FOUR WIRE CONNECTOR FROM THE ECM. THE CONNECTOR TERMINALS ARE LETTERED AS SHOWN IN FIGURE 85. THESE CIRCUITS PERFORM THE FOLLOWING FUNCTIONS: - REFERENCE GROUND - TERMINAL A. THIS WIRE IS GROUNDED IN THE DISTRIBUTOR AND MAKES SURE THE GROUND CIRCUIT HAS NO VOLTAGE DROP WHICH COULD AFFECT PERFORMANCE. IF IT IS OPEN, IT MAY CAUSE POOR PERFORMANCE. - BY-PASS - TERMINAL B. AT ABOUT 400 RPM, THE ECM APPLIES 5 VOLTS TO THIS CIRCUIT TO SWITCH SPARK TIMING CONTROL FROM THE HEI MODULE TO THE ECM. AN OPEN OR GROUNDED BYPASS CIRCUIT WILL SET A CODE 42 AND THE ENGINE WILL RUN AT BASE TIMING, PLUS A SMALL AMOUNT OF ADVANCE BUILT INTO THE HEI MODULE. - DISTRIBUTOR REFERENCE - TERMINAL C. THIS PROVIDES THE ECM WITH RPM AND CRANKSHAFT POSITION INFORMATION. - EST - TERMINAL D. THIS CIRCUIT TRIGGERS THE HEI MODULE. THE ECM DOES NOT KNOW WHAT THE ACTUAL TIMING IS, BUT IT DOES KNOW WHEN IT GETS THE REFERENCE SIGNAL. IT THEN ADVANCES OR RETARDS THE SPARK FROM THAT POINT. THEREFORE, IF THE BASE TIMING IS SET INCORRECTLY, THE ENTIRE SPARK CURVE WILL BE INCORRECT. RESULTS OF INCORRECT OPERATION AN OPEN OR GROUND IN THE EST CIRCUIT WILL SET A CODE 42 AND CAUSE THE ENGINE TO RUN ON THE HEI MODULE TIMING. THIS WILL CAUSE POOR PERFORMANCE AND POOR FUEL ECONOMY. THE ECM USES INFORMATION FROM THE MAP AND COOLANT SENSORS IN ADDITION TO RPM TO CALCULATE SPARK ADVANCE AS FOLLOWS: - LOW MAP OUTPUT VOLTAGE = MORE SPARK ADVANCE - COLD ENGINE = MORE SPARK ADVANCE - HIGH MAP OUTPUT OUTPUT VOLTAGE = LESS SPARK ADVANCE - HOT ENGINE - LESS SPARK ADVANCE THEREFORE, DETONATION COULD BE CAUSED BY LOW MAP OUTPUT OR HIGH RESISTANCE IN THE COOLANT SENSOR CIRCUIT. POOR PERFORMANCE COULD BE CAUSED BY HIGH MAP OUTPUT OR LOW RESISTANCE IN THE COOLANT SENSOR CIRCUIT. HOW CODE 42 IS DETERMINED WHEN THE SYSTEM IS RUNNING ON THE HEI MODULE, THAT IS, NO VOLTAGE ON THE BY-PASS LINE, THE HEI MODULE GROUNDS THE EST SIGNAL. THE ECM EXPECTS TO SEE NO VOLTAGE ON THE EST LINE DURING THIS CONDITION. IF IT SEES A VOLTAGE, IT SETS CODE 42 AND WILL NOT GO INTO THE EST MODE. WHEN THE RPM FOR EST IS REACHED (ABOUT 400 RPM) THE ECM APPLIES 5 VOLTS TO THE BY-PASS LINE AND THE EST SHOULD NO LONGER BE GROUNDED IN THE HEI MODULE SO THE EST VOLTAGE SHOULD BE VARYING. IF THE BY-PASS LINE IS OPEN OR GROUNDED, THE HEI MODULE WILL NOT SWITCH TO EST MODE SO THE EST VOLTAGE WILL BE LOW AND CODE 42 WILL BE SET. DIAGNOSIS THE DESCRIPTION, OPERATION, AND DIAGNOSIS OF THE HEI SYSTEM ARE FOUND IN SECTION 6D OF THIS MANUAL. CODE 12 CODE 12 IS USED DURING THE DIAGNOSTIC CIRCUIT CHECK PROCEDURE TO TEST THE CODE DISPLAY ABILITY OF THE ECM. THIS CODE INDICATES THAT THE ECM IS NOT RECEIVING THE ENGINE RPM (REFERENCE) SIGNAL. THIS OCCURS WITH THE IGNITION KEY "ON" AND THE ENGINE NOT RUNNING. THE "REFERENCE" SIGNAL ALSO TRIGGERS THE FUEL INJECTION SYSTEM. WITHOUT THE "REFERENCE" SIGNAL THE ENGINE CANNOT RUN. CHECKING EST PERFORMANCE THE ECM WILL SET TIMING AT A SPECIFIED VALUE WHEN THE DIAGNOSTIC "TEST" TERMINAL IN THE ALCL CONNECTOR IS GROUNDED. TO CHECK FOR EST OPERATION, THE TIMING SHOULD BE CHECKED AT 2000 RPM WITH THE TERMINAL UNGROUNDED. THEN GROUND THE "TEST" TERMINAL. IF THE TIMING CHANGES AT 2000 RPM, THE EST IS OPERATING. A FAULT IN THE EST SYSTEM WILL USUALLY SET A TROUBLE CODE 42. USE THAT CHART TO DIAGNOSE THE SYSTEM.

6E2-78B DRIVEABILITY AND EMISSIONS - FUEL INJECTION (TBI) THE PRESSURE REGULATOR IS SERVICED AS PART OF THE FUEL METER COVER. IF THE PRESSURE REGULATOR IN THE TBI SUPPLIES PRESSURE WHICH IS TOO LOW (BELOW 62 KPA OR 9 PSI) POOR PERFORMANCE COULD RESULT. IF THE PRESSURE IS TOO HIGH, DETONATION AND EXCESSIVE ODOR MAY RESULT. IDLE AIR CONTROL (IAC) VALVE THE PURPOSE OF THE IDLE AIR CONTROL (IAC) VALVE (SHOWN IN FIGURE 27), IS TO CONTROL ENGINE IDLE SPEED, WHILE PREVENTING STALLS DUE TO CHANGES IN ENGINE LOAD. THE IAC VALVE, MOUNTED ON THE THROTTLE BODY, CONTROLS BYPASS AIR AROUND THE THROTTLE PLATE. BY MOVING A CONICAL VALVE IN (TO DECREASE AIR FLOW) OR OUT (TO INCREASE AIR FLOW), A CONTROLLED AMOUNT OF AIR CAN MOVE AROUND THE THROTTLE PLATE. IF RPM IS TOO LOW, MORE AIR IS BYPASSED AROUND THE THROTTLE VALVE TO INCREASE RPM. IF RPM IS TOO HIGH, LESS AIR IS BYPASSED AROUND THE THROTTLE PLATE TO DECREASE RPM. THE IAC VALVE MOVES IN SMALL STEPS CALLED "COUNTS", WHICH CAN BE MEASURED BY SOME TEST EQUIPMENT WHICH PLUGS INTO THE ALCL. DURING IDLE, THE PROPER POSITION OF THE IAC VALVE IS CALCULATED BY THE ECM BASED ON BATTERY VOLTAGE, COOLANT TEMPERATURE, ENGINE LOAD, AND ENGINE RPM. IF THE RPM DROPS BELOW A SPECIFIED RPM, AND THE THROTTLE PLATE IS CLOSED, THE ECM SENSES A NEAR STALL CONDITION. THE ECM WILL THEN CALCULATE A NEW VALVE POSITION BASED ON BAROMETRIC PRESSURE TO PREVENT STALLS. IF THE IAC VALVE IS DISCONNECTED OR CONNECTED WITH THE ENGINE RUNNING, THE IAC COUNTS MAY BE WRONG. IN TH IS CASE, THE IAC HAS TO BE RESET BY RUNNING THE VEHICLE OVER 35 MPH (56 KM/H) WITH THE CIRCUIT CONNECTED NORMALLY. THREE DIFFERENT DESIGNS ARE USED FOR THE CONICAL VALVE (SEE FIGURE 73). THE FIRST DESIGN, USED ON 2.5L ENGINES, IS A SINGLE 35 DEGREES TAPER. THE SECOND DESIGN, USED ON 1.8L ENGINES AND 2.0L ENGINES WITH AUTOMATIC TRANSMISSIONS, IS A DUAL TAPER. THE THIRD DESIGN, USED ON 2.0L ENGINES WITH MANUAL TRANSMISSIONS, IS A BLUNT VALVE. BE SURE TO USE THE CORRECT DESIGN WHEN REPLACEMENT IS REQUIRED. THE IAC VALVE AFFECTS ONLY THE IDLE CHARACTERISTICS OF THE VEHICLE. IF IT IS OPEN FULLY, TOO MUCH AIR WILL BE ALLOWED TO THE MANIFOLD AND IDLE SPEED WILL BE HIGH. IF IT IS STUCK CLOSED, TOO LITTLE AIR WILL BE ALLOWED IN THE MANIFOLD, AND IDLE SPEED WILL BE TOO LOW. FUEL PUMP ELECTRICAL CIRCUIT WHEN THE KEY IS FIRST TURNED ON WITHOUT THE ENGINE RUNNING, THE ECM WILL TURN THE FUEL PUMP RELAY ON FOR TWO SECONDS. THIS BUILDS UP THE FUEL PRESSURE QUICKLY. IF THE ENGINE IS NOT STARTED WITHIN TWO SECONDS, THE ECM WILL SHUT THE FUEL PUMP OFF AND WAIT UNTIL THE 2. CANISTER INSTALL OR CONNECT 1. CANISTER. 2. HOSES. MAKE SURE CONNECTIONS ARE CORRECT.

DRIVEABILITY AND EMISSIONS - FUEL INJECTION (TBI) 6E2-78A CANISTER HOSES REFER TO VEHICLE EMISSION CONTROL INFORMATION LABEL FOR ROUTING OF CANISTER HOSES. WHEN REPLACING HOSES, USE HOSE IDENTIFIED WITH THE WORD "FLUOROELASTOMER". VAPOR PIPE THE VAPOR PIPE IS SECURED TO THE UNDERBODY WITH CLAMP AND SCREW ASSEMBLIES. FLEXIBLE HOSES ARE CONNECTED AT THE FUEL TANK AND THE FUEL VAPOR CANISTER. THE PIPE SHOULD BE INSPECTED OCCASIONALLY FOR LEAKS, KINKS OR DENTS AND REPAIRED AS REQUIRED. REPAIR REPAIR VAPOR PIPE IN SECTIONS USING BRAZED SEAMLESS STEEL TUBING MEETING GM SPECIFICATION 123M OR ITS EQUIVALENT OR HOSE IDENTIFIED WITH THE WORDS "FLUOROELASTOMER". HOSE NOT SO MARKED COULD CAUSE EARLY FAILURE TO MEET EMISSION STANDARD. - DO NOT USE COPPER OR ALUMINIUM TUBING TO REPLACE STEEL TUBING. THOSE MATERIALS DO NOT HAVE SATISFACTORY DURABILITY TO WITHSTAND NORMAL VEHICLE VIBRATIONS. - DO NOT USE RUBBER HOSE WITHIN 4 INCH (100 MM) ON ANY PART OF THE EXHAUST SYSTEM OR WITHIN 10" (254 MM) OF THE CATALYTIC CONVERTER. HOSE INSIDE DIAMETER MUST MATCH STEEL TUBING OUTSIDE DIAMETER. 1. IN REPAIRABLE AREAS, CUT A PIECE OF FUEL HOSE 4" (100 MM) LONGER THAN PORTION OF THE LINE REMOVED. IF MORE THAN A 6 INCH (152 MM) LENGTH OF PIPE IS REMOVED, USE A COMBINATION OF STEEL TUBING AND HOSE SO THAT HOSE LENGTHS WILL NOT BE MORE THAN 10 INCHES (254 MM). 2. CUT ENDS OF PIPE REMAINING ON VEHICLE SQUARE WITH A TUBE CUTTER. USING THE FIRST STEP OF A DOUBLE FLARING TOOL, FORM A BEAD ON THE END OF BOTH PIPE SECTIONS. IF PIPE IS TOO CORRODED TO WITHSTAND BEAD OPERATION WITHOUT DAMAGE, THE PIPE SHOULD BE REPLACED. IF A NEW SECTION OF PIPE IS USED, FORM A BEAD ON BOTH ENDS OF IT ALSO. 3. USE SCREW TYPE HOSE CLAMP, P/N 2494772, OR EQUIVALENT. SLIDE CLAMPS ONTO PIPE AND PUSH HOSE 2" (51 MM) ONTO EACH PORTION OF FUEL PIPE. TIGHTEN CLAMPS ON EACH SIDE OF REPAIR. FUEL CAP IF A FUEL TANK FILLER CAP REQUIRES REPLACEMENT, USE ONLY A CAP WITH THE SAME FEATURES. FAILURE TO USE THE CORRECT CAP CAN RESULT IN A MALFUNCTIONING OF THE SYSTEM. PARTS INFORMATION PART NAME...........................GROUP CANISTER, FUEL VAPOR................3.130 SOLENOID, FUEL VAPOR CANISTER.......3.140

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.