Feedback Carburetor Component Test GMC Vandura I

System Performance Check Chart. Scheme 94

Diagnostic Circuit Check Chart. Scheme 95

ENGINE PERFORMANCE PROBLEM - ODOR, SURGE, FUEL ECONOMY OR EMISSION PROBLEM

1. If the "CHECK ENGINE" light is not on, normal checks that would be performed on cars without the system should be done first.
2. If the alternator or coolant light is on with the "CHECK ENGINE" light, they should be diagnosed first.
3. Inspect for poor connections at coolant sensor, mixture control solenoid, etc. Also check for poor or loose vacuum hoses and connections. Repair as necessary.
4. If there is an intermittent "CHECK ENGINE" light, but no trouble code is stored, check the following: Check for intermittent connection in circuit between ignition coil to ground. Check for arcing at spark plug wires or spark plugs. Check battery to ECM terminals "C" and "R". Check ECM Terminals "A" and "U" to engine ground. Check for loss of trouble code long-term memory: Grounding dwell lead for 10 seconds with "TEST" lead ungrounded should produce a Code 23 which should be retained after the engine is turned off and the ignition switch is turned to "RUN" position. If a Code 23 is not displayed, ECM is defective and must be replaced. Ensure that the EST wires are kept away from the spark plug wires, distributor housing, ignition coil and alternator. Wires from ECM Terminal No. 13 to distributor and the shield (if used) should have a good ground.
5. If the customer is complaining of stalling, rough idle, dieseling or improper idle speed, see IDLE SPEED CONTROL CHECK.
6. If the complaint is detonation (spark knock) check the following items: Check the ESC system. Refer to ESC SYSTEM CHECK. Check the MAP or Vacuum Sensor output. See CHART 7 - MAP & BARO OUTPUT CHECK or CHART 8 - VACUUM SENSOR CHECK. Check EGR system. Refer to EGR VALVE CHECK. Check TPS enrichment system operation. See TPS ENRICHMENT CHECK. Check HEI operation. Refer to appropriate IGNITION SYSTEM article in the ELECTRICAL section.
7. If the complaint is poor performance and/or poor fuel economy, check the following: Perform appropriate EST PERFORMANCE CHECK. Perform ESC SYSTEM CHECK.
8. If the customer is experiencing poor full throttle performance, refer to CRANKS, BUT WON'T RUN chart.
9. If the complaint is intermittent no starts, make the following checks: Check for incorrect pick-up coil or ignition coil. See CRANKS, BUT WON'T RUN chart. Check for intermittent ground connection on ECM.

ALL OTHER COMPLAINTS

For any other complaints, do the SYSTEM PERFORMANCE CHECK with engine warmed to normal operating temperature. Ensure all repairs have been made to vehicle before performing SYSTEM PERFORMANCE CHECK.

CHART 1 - Dwell Fixed Under 10° (Lean Exhaust Indication). Scheme 96

CHART 2 - Dwell Between 10°-50° Open Coolant/O2 Sensor Ckt. Scheme 97

CHART 3 - Fixed Dwell Over 50° (Rich Exhaust Indication). Scheme 98

CHART 4 - TPS Enrichment Check. Scheme 99

CHART 5 - "CHECK ENGINE" Light Inoperative. Scheme 100

CHART 6 - Won't Flash Code 12 (Remote Lamp Driver In Harness). Scheme 101

CHART 7 - Map & Baro Output Check. Scheme 102

CHART 8 - Vacuum Sensor Check. Scheme 103

Flow Chart - Canister Purge Valve Check. Scheme 104

Flow Chart - Canister Purge Valve Check. Scheme 105

Flow Chart - Divert Valve Check. Scheme 106

Flow Chart - Divert Valve Check (1 Of 2). Scheme 107

Flow Chart - Divert Valve Check (2 Of 2). Scheme 108

Flow Chart - Air Mgmt Sys Chk W/ Elec Air Cont & Elec Switch Valve. Scheme 109

Flow Chart - Air Mgmt Sys Chk W/ Elec Air Cont & Elec Switch Valve. Scheme 110

Flow Chart - EFE (Electrically Heated) Check (3.8L Turbo). Scheme 111

Flow Chart - EFE (Electrically Heated) Check (3.8L Turbo). Scheme 112

Flow Chart - EFE (Electrically Heated) Chk (Exc 3.8L Turbo). Scheme 113

Flow Chart - EFE (Electrically Heated) Chk (Exc 3.8L Turbo). Scheme 114

Flow Chart - EFE (Vacuum Servo) Check. Scheme 115

Flow Chart - EFE (Vacuum Servo) Check. Scheme 116

Flow Chart - EGR Valve Chk (3.8L VIN A/Cal, 4.1L & 5.0L VIN Y). Scheme 117

Flow Chart - EGR Valve Chk (3.8L VIN A/Cal, 4.1L & 5.0L VIN Y). Scheme 118

Flow Chart - Electric Diverter Valve Check (EDV) 3.8L VIN "A"/Calif., 5.0L VIN "H"/Calif. - "B" & "G" Series, & 5.7L Calif. Scheme 119

Flow Chart - Electric Diverter Valve Check (EDV) 3.8L VIN "A"/Calif., 5.0L VIN "H"/Calif. - "B" & "G" Series, & 5.7L Calif. Scheme 120

Flow Chart - Electronic Spark Control (ESC) System Check (Engine Knock, Poor Performance Or Poor Economy) - No Code 43. Scheme 121

Flow Chart - Electronic Spark Control (ESC) System Check (Engine Knock, Poor Performance Or Poor Economy) - No Code 43. Scheme 122

Flow Chart - Engine Cranks, But Won't Run (W/Integral Coil). Scheme 123

Flow Chart - Engine Cranks, But Won't Run (With Remote Coil). Scheme 124

Flow Chart - EST Performance Check (Exc. 5.0L VIN "Y" & "9"). Scheme 125

Flow Chart - EST Performance Check (Exc. 5.0L VIN "Y" & "9"). Scheme 126

Flow Chart - EST Performance Check (5.0L VIN "Y" & "9"). Scheme 127

Flow Chart - EST Performance Check (5.0L VIN "Y" & "9"). Scheme 128

Flow Chart - Idle Speed Control (ISC) Check. Scheme 129

Flow Chart - Idle Speed Control (ISC) Check. Scheme 130

Flow Chart - Pulsair Solenoid Check. Scheme 131

Flow Chart - Pulsair Solenoid Check. Scheme 132

Flow Chart - Pulse Width Modulated (PWM) EGR Check - 2.8L, 3.0L, 3.8L (Exc. 3.8L VIN "A" Calif.), 5.0L VIN "H" & 5.7L VIN "L". Scheme 133

Flow Chart - Pulse Width Modulated (PWM) EGR Check - 2.8L, 3.0L, 3.8L (Exc. 3.8L VIN "A" Calif.), 5.0L VIN "H" & 5.7L VIN "L". Scheme 134

Flow Chart - Torque Converter Clutch (TCC) Elec Diagnosis. Scheme 135

Flow Chart - Torque Converter Clutch (TCC) Elec Diagnosis (1 Of 2). Scheme 136

Flow Chart - Torque Converter Clutch (TCC) Elec Diagnosis (2 Of 2). Scheme 137