Feedback Carburetor Component Test Chevrolet Van I

System Performance Check Chart. Scheme 80

Diagnostic Circuit Check Chart. Scheme 81

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 82

CHART 2 - Dwell Between 10°-50° Open Coolant/O2 Sensor Ckt. Scheme 83

CHART 3 - Fixed Dwell Over 50° (Rich Exhaust Indication). Scheme 84

CHART 4 - TPS Enrichment Check. Scheme 85

CHART 5 - "CHECK ENGINE" Light Inoperative. Scheme 86

CHART 6 - Won't Flash Code 12 (Remote Lamp Driver In Harness). Scheme 87

CHART 7 - Map & Baro Output Check. Scheme 88

CHART 8 - Vacuum Sensor Check. Scheme 89

Flow Chart - Canister Purge Valve Check. Scheme 90

Flow Chart - Canister Purge Valve Check. Scheme 91

Flow Chart - Divert Valve Check. Scheme 92

Flow Chart - Divert Valve Check (1 Of 2). Scheme 93

Flow Chart - Divert Valve Check (2 Of 2). Scheme 94

Flow Chart - Air Mgmt Sys Chk W/ Elec Air Cont & Elec Switch Valve. Scheme 95

Flow Chart - Air Mgmt Sys Chk W/ Elec Air Cont & Elec Switch Valve. Scheme 96

Flow Chart - EFE (Electrically Heated) Check (3.8L Turbo). Scheme 97

Flow Chart - EFE (Electrically Heated) Check (3.8L Turbo). Scheme 98

Flow Chart - EFE (Electrically Heated) Chk (Exc 3.8L Turbo). Scheme 99

Flow Chart - EFE (Electrically Heated) Chk (Exc 3.8L Turbo). Scheme 100

Flow Chart - EFE (Vacuum Servo) Check. Scheme 101

Flow Chart - EFE (Vacuum Servo) Check. Scheme 102

Flow Chart - EGR Valve Chk (3.8L VIN A/Cal, 4.1L & 5.0L VIN Y). Scheme 103

Flow Chart - EGR Valve Chk (3.8L VIN A/Cal, 4.1L & 5.0L VIN Y). Scheme 104

Flow Chart - Electric Diverter Valve Check (EDV) 3.8L VIN "A"/Calif., 5.0L VIN "H"/Calif. - "B" & "G" Series, & 5.7L Calif. Scheme 105

Flow Chart - Electric Diverter Valve Check (EDV) 3.8L VIN "A"/Calif., 5.0L VIN "H"/Calif. - "B" & "G" Series, & 5.7L Calif. Scheme 106

Flow Chart - Electronic Spark Control (ESC) System Check (Engine Knock, Poor Performance Or Poor Economy) - No Code 43. Scheme 107

Flow Chart - Electronic Spark Control (ESC) System Check (Engine Knock, Poor Performance Or Poor Economy) - No Code 43. Scheme 108

Flow Chart - Engine Cranks, But Won't Run (W/Integral Coil). Scheme 109

Flow Chart - Engine Cranks, But Won't Run (With Remote Coil). Scheme 110

Flow Chart - EST Performance Check (Exc. 5.0L VIN "Y" & "9"). Scheme 111

Flow Chart - EST Performance Check (Exc. 5.0L VIN "Y" & "9"). Scheme 112

Flow Chart - EST Performance Check (5.0L VIN "Y" & "9"). Scheme 113

Flow Chart - EST Performance Check (5.0L VIN "Y" & "9"). Scheme 114

Flow Chart - Idle Speed Control (ISC) Check. Scheme 115

Flow Chart - Idle Speed Control (ISC) Check. Scheme 116

Flow Chart - Pulsair Solenoid Check. Scheme 117

Flow Chart - Pulsair Solenoid Check. Scheme 118

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 119

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 120

Flow Chart - Torque Converter Clutch (TCC) Elec Diagnosis. Scheme 121

Flow Chart - Torque Converter Clutch (TCC) Elec Diagnosis (1 Of 2). Scheme 122

Flow Chart - Torque Converter Clutch (TCC) Elec Diagnosis (2 Of 2). Scheme 123