Engine Controls - Tests W/o Codes - Efi Toyota Supra A70

GENERAL INFORMATION

Use this section to diagnose driveability problems that exist when a hard fault code is not present. Symptom checks are intended to direct the technician to malfunctioning component(s) for further diagnosis. A "symptom" should lead to further testing of specific components or systems, or verification of adjustment specifications.

This article will cover 3 areas of trouble shooting fuel injected vehicles when diagnostic codes are not present

1. Symptom Diagnostics
2. Intermittent Diagnosis
3. Turbocharger Diagnosis

Specific Component or System Test Procedures

1989

4-Cylinder, see: SYSTEM/COMPONENT TESTS - EFI

6-Cylinder, see: SYSTEM/COMPONENT TESTS - EFI

V6, see: SYSTEM/COMPONENT TESTS - EFI

1990

4-Cylinder, see: SYSTEM/COMPONENT TESTS - EFI

6-Cylinder, see: SYSTEM/COMPONENT TESTS - EFI

V6, see: SYSTEM/COMPONENT TESTS - EFI

Tune-Up Specifications

1989

4-Cylinder, see: SPECIFICATIONS - 4-CYL

6-Cylinder, see: SPECIFICATIONS - 6-CYL

V6, see: SPECIFICATIONS - V6

1990

4-Cylinder, see: SPECIFICATIONS - 4-CYL

6-Cylinder, see: SPECIFICATIONS - 6-CYL

V6, see: SPECIFICATIONS - V6

Tune-Up Adjustment Procedures

1989

4-Cylinder, see: ADJUSTMENTS - 4-CYL EFI

6-Cylinder, see: ADJUSTMENTS - 6-CYL

V6, see: ADJUSTMENTS - V6

1990

4-Cylinder, see: ADJUSTMENTS - 4-CYL EFI

6-Cylinder, see: ADJUSTMENTS - 6-CYL

V6, see: ADJUSTMENTS - V6 EFI

SYMPTOM DIAGNOSTICS

Symptom checks cannot be used properly unless the problem occurs while the vehicle is tested. To reduce diagnostic time, ensure steps in the appropriate BASIC TESTING and TESTS W/CODES articles (if applicable) have been performed before attempting to diagnose a symptom. Refer to the following menu

BASIC DIAGNOSIS

1. 4-Cylinder 1989, see: «BASIC TESTING - 4-CYL EFI»(ref-20867) 1990, see: «BASIC TESTING - EFI»(ref-20889)
2. 6-Cylinder 1989, see: «BASIC TESTING - 6-CYL»(/toyota/supra/a70-1986-1993/remont/testing-diagnostics/#basic-testing-6-cyl) 1990, see: «BASIC TESTING - 6-CYL»(/toyota/supra/a70-1986-1993/remont/testing-diagnostics/#basic-testing-6-cyl)
3. V6 1989, see: «BASIC TESTING - V6»(ref-20869) 1990, see: «BASIC TESTING - EFI»(ref-20889)

CODE TESTING

1. Corolla «TESTS W/CODES»(ref-20872) - 1989 «TESTS W/CODES»(ref-20890) - 1990
2. Camry «TESTS W/CODES - EFI»(ref-20870)
3. Celica «TESTS W/CODES»(ref-20871)
4. Cressida «TESTS W/CODES - EFI»(ref-20873)
5. Land Cruiser «TESTS W/CODES - EFI»(ref-20874)
6. Pickup & 4Runner «TESTS W/CODES - 4-CYL EFI»(ref-20891) - 4-Cyl. 1989 «TESTS W/CODES - 4-CYL EFI»(ref-20892) - 4-Cyl. 1990 «TESTS W/CODES - V6»(ref-20893)
7. Supra «TESTS W/CODES - EFI»(/toyota/supra/a70-1986-1993/remont/testing-diagnostics/#engine-controls-tests-wcodes-efi)
8. Tercel «TESTS W/CODES - EFI»(ref-20894) - 1990 only
9. Van «TESTS W/CODES - EFI»(ref-20879) - 1989 only Symptoms available for diagnosis include the following

SYMPTOM-TO-DIAGNOSIS MENU

SYMPTOM-TO-DIAGNOSIS MENU

NO START/CRANKS SLOWLY

1. Check battery and cables, charging system and fusible links.
2. Check ignition switch.
3. Check starter relay (M/T).
4. Check clutch start switch (M/T) or neutral start switch (A/T).
5. Check starter and wiring connections.

NO START/CRANKS OKAY

1. Check for vacuum leaks.
2. Verify secondary ignition system performance.
3. Ensure ignition timing is correct.
4. Check auxiliary air valve (if equipped).
5. Ensure fuel system (pump, lines, filter and pressure regulator) performs properly.
6. Verify proper compression and valve clearance.
7. Check circuit opening relay.
8. If engine starts with accelerator pedal depressed, check idle speed control valve (if equipped) and wiring connection.
9. Check fuel pump switch in airflow meter.
10. Check wiring connection to ECU.
11. Check power to ECU via fusible links, fuses and EFI main relay.
12. Check airflow meter, coolant temperature sensor and air temperature sensor.
13. Check injection signal circuit.

ENGINE STALLS OFTEN

1. Check for vacuum leaks.
2. Ensure fuel system (pump, lines, filter and pressure regulator) performs properly.
3. Check air filter.
4. Check idle speed and ensure ignition timing is correct.
5. Verify secondary ignition system performance.
6. Verify proper compression and valve clearance.
7. Check cold start injector and cold start injector time switch.
8. Check auxiliary air valve (if equipped) or idle speed control valve (if equipped).
9. Check circuit opening relay.
10. Check fuel injectors.
11. Check power to ECU via fusible links, fuses and EFI main relay.
12. Check airflow meter, coolant temperature sensor and air temperature sensor.
13. Check injection signal circuit.

ENGINE STALLS SOMETIMES

1. Check airflow meter and connectors.
2. Check vacuum sensor (Corolla 4A-FE).
3. Check EFI main relay, circuit opening relay and connectors. (Check for slight change in engine idle when connector or relay are slightly tapped or wiggled.)

ROUGH IDLE/MISSING

1. Check for vacuum leaks.
2. Check air filter.
3. Check idle speed and ensure ignition timing is correct.
4. Verify secondary ignition system performance.
5. Verify proper compression and valve clearance.
6. Check variable induction system (if equipped).
7. Check cold start injector and cold start injector time switch.
8. Ensure fuel system (pump, lines, filter and pressure regulator) performs properly.
9. Check fuel injectors.
10. Check power to ECU via fusible links, fuses and EFI main relay.
11. Check airflow meter, coolant temperature sensor and air temperature sensor.
12. Check injection signal circuit.
13. Check O2 sensor(s).

HIGH IDLE SPEED

1. Check accelerator linkage.
2. Check power steering idle-up circuit (if equipped).
3. Check A/C idle-up circuit (if equipped).
4. Check idle speed control valve (if equipped) or auxiliary air valve (if equipped) and wiring.
5. Check variable induction system (if equipped).
6. Ensure ignition timing is correct.
7. Check throttle position sensor.
8. Check for high fuel pressure.
9. Check for leakage at cold start injector or fuel injectors.
10. Check power to ECU via fusible links, fuses and EFI main relay.
11. Check airflow meter, coolant temperature sensor and air temperature sensor.
12. Check injection signal circuit.

ENGINE BACKFIRES

1. Check for vacuum leaks.
2. Check idle speed and ensure ignition timing is correct.
3. Check cold start injector and cold start injector time switch.
4. Ensure fuel system (pump, lines, filter and pressure regulator) performs properly.
5. Check for clogged fuel injectors.
6. Check power to ECU via fusible links, fuses and EFI main relay.
7. Check airflow meter, coolant temperature sensor, throttle position sensor and air temperature sensor.
8. Check injection signal circuit.
9. Check O2 sensor(s).

MUFFLER EXPLOSION

1. Check idle speed and ensure ignition timing is correct.
2. Check cold start injector and cold start injector time switch.
3. Ensure fuel system (pump, lines, filter and pressure regulator) performs properly.
4. Check for fuel injector leakage.
5. Verify secondary ignition system performance.
6. Verify proper compression and valve clearance.
7. Check throttle position sensor, injection signal circuit and O2 sensor(s).

ENGINE HESITATES

1. Check for clutch slipping or brakes dragging.
2. Check for vacuum leaks.
3. Check air filter.
4. Verify secondary ignition system performance and timing.
5. Verify proper compression and valve clearance.
6. Ensure fuel system (pump, lines, filter and pressure regulator) performs properly.
7. Check for clogged fuel injectors.
8. Check variable induction system (if equipped).
9. Check power to ECU via fusible links, fuses and EFI main relay.
10. Check airflow meter, coolant temperature sensor, air temperature sensor and throttle position sensor.
11. Check injection signal circuit.

INTRODUCTION

Use this section to locate intermittent driveability problems that do not occur when the vehicle is being tested. These problems may cause a noticeable driveability problem or cause the "CHECK ENGINE" light to illuminate on some vehicles. Before attempting to diagnose an intermittent fault, ensure steps in BASIC TESTING and TESTS W/CODES (if applicable) have been performed.

Intermittent fault testing requires duplicating a circuit or component failure to identify the fault. These procedures may lead to the computer recording a fault code (on some systems), which may help in diagnosis.

INTERMITTENT SIMULATION

Use the following methods to produce conditions for creating an intermittent fault during testing

1. Apply light vibration to components.
2. Heat a component.
3. Wiggle or bend a wiring harness.
4. Apply moisture to a component.
5. Remove or apply a vacuum supply source.

While attempting to simulate an intermittent, observe component voltage and/or self-diagnostic codes. Use these test results to identify a faulty component or potential problem area.

An intermittent problem is defined as one that does NOT happen while you are testing the system or actually running through self-diagnosis system steps.

If "CHECK ENGINE" light does come "ON", the ECU may store a trouble code in memory. The trouble codes usually only set in memory if the circuit fails (high or low). If a sensor drifts out of specification, a trouble code may not set. To locate sensors out of specification, test ECU signals using appropriate J - PIN VOLTAGE charts in this section.

DIAGNOSIS & TESTING

To properly diagnose an intermittent problem requires special test methods to create the intermittent problem(s). These methods include applying light vibration, heat and humidity.

Wiring Harness Testing

If vibration is suspected as cause of an intermittent, lightly shake wiring harness vertically and horizontally while monitoring suspected circuit or component with a DVOM. Look for a voltage fluctuation during this test procedure. Inspect connector joint, fulcrum of the vibration and body through-portion. (Scheme 52)

Component and Sensor Testing

Lightly vibrate suspect component, relay or sensor, while monitoring suspected circuit or component with a DVOM. Look for a voltage fluctuation during this test procedure. (Scheme 52)

Electrical Connector Testing

Lightly shake connector vertically and horizontally, while monitoring suspected circuit or component with a DVOM. Look for a voltage fluctuation during this test procedure. Visually inspect connector and repair as required.

Scheme 52

HEAT METHOD

Apply heat to a suspected component with a hair dryer or similar device and monitor suspected circuit or component with a DVOM.

Note. DO NOT heat any component to more than 140°F (60°C). DO NOT apply heat directly to any part of the ECU.

HUMIDITY METHOD

If humidity or moisture are suspected of causing an intermittent failure, spray water on the radiator. Check to see if a malfunction occurs by monitoring the suspected circuit or component with a DVOM.

If a vehicle is subject to water leakage, the admitted water may contaminate the ECU. When testing a vehicle where water leakage has occurred, carefully inspect the ECU terminals for corrosion. Repair or replace the ECU connectors as required.

ELECTRICAL LOAD METHOD

To check if an intermittent occurs under electrical load, turn on all electrical loads (heater blower, headlights, rear window defogger, etc.). Check to see if the malfunction will occur by monitoring the suspected circuit or component with a DVOM.

TURBOCHARGER DIAGNOSIS

Note. Check the following items. If found defective, replace turbocharger assembly. If related parts are defective, repair or replace.

VIBRATION OR NOISE

1. Inspect for defective bearings or interference of rotating parts with related objects. Consider neglect of engine oil change, sustained use with contamination in oil pipe, a restricted or broken oil filter. Check for repeated abrupt starts and stops that could cause bearing failure.
2. If nothing is wrong with lubricating system, an incorrectly balanced rotating section or bent shaft may be suspected. This is due to excessive wear of bearings or contamination that have caused damage to turbine or compressor wheels.
3. If any of these conditions exist, turbocharger assembly must be replaced. Before a new turbocharger assembly is installed, carefully check for contamination or pieces of broken turbine or compressor wheels which might be left in manifold system.

LOW BOOST PRESSURE

1. Check air cleaner element for contamination or clogging. Clean or replace element as necessary. If turbine or compressor wheels do not rotate smoothly and lightly when turned by hand, replace turbocharger assembly. Check wastegate valve or relief valve which might be left opened.
2. If turbocharger appears good, but has low boost pressure, check for the following: Leaks in exhaust system. Deformed or restricted exhaust pipe or muffler which might be causing increased back pressure. Air leaks from compressor discharge side.

WHITE EXHAUST SMOKE

Sustained engine operation with faulty bearings will result in failure of oil seal, which could cause leakage of engine oil into exhaust and intake pipes. Leakage of engine oil from turbocharger into exhaust pipe or intake pipe will result in White-colored exhaust. If this occurs, check for clogged, crushed or deformed oil return pipe. If nothing is wrong with oil return pipe, leakage is probably due to wear of piston ring (seal ring) in turbocharger.

See also:
• BASIC TESTING - 6-CYL
• TESTS W/CODES - EFI
• NO START/CRANKS SLOWLY
• NO START/CRANKS OKAY
• ENGINE STALLS OFTEN
• ENGINE STALLS SOMETIMES
• ROUGH IDLE/MISSING
• HIGH IDLE SPEED
• ENGINE BACKFIRES
• MUFFLER EXPLOSION
• ENGINE HESITATES