Honda Civic/CRX/del Sol 1984-1995 Repair Guide

Relieving Fuel System Pressure

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It is important to release the pressure in the fuel system before performing any work on it. Fuel under pressure could be sprayed onto hot engine components and possibly ignite.

  1. Make sure the engine is cold.
  2.  
  3. Disconnect the negative battery cable.
  4.  
  5. Remove the fuel filler cap.
  6.  
  7. Use a suitable box end wrench on the 6mm service bolt at the top of the fuel filter, while holding the special banjo bolt with another wrench.
  8.  
  9. Place a rag or shop towel over the 6mm service bolt.
  10.  
  11. Slowly loosen the 6mm service bolt one complete turn and allow the pressurized fuel to de-pressurize.
  12.  
  13. Unless the work you are performing requires removal of the service bolt, re-tighten the bolt, once the fuel pressure is relieved, to 11 ft. lbs. (15 Nm).
  14.  

COMPONENT TEST PROCEDURES



Detailed tests for 1988-95 models can be found in the Troubleshooting Flowcharts in Emission Controls .

Oxygen Sensor

See Figure 1

1985-87 MODELS
  1. Unplug the oxygen sensor connector.
  2.  
  3. Start engine and warm up for two minutes at 3000 rpm under no load. Raise engine speed to 4000 rpm and release throttle suddenly at least 5 times.
  4.  
  5. Within one minute after engine has been warmed up, measure voltage between connector terminal and body ground as described in Steps 4 and 5.
  6.  

If it takes more than one minute to complete checks, warm engine as in Step 2 before continuing.

  1. Raise engine speed to 5000 rpm, then lower to 2000 rpm by operating accelerator pedal, immediately turn ignition switch OFF . Voltage should be below 0.4 volts.
  2.  
  3. Disconnect the MAP sensor vacuum tube from the throttle body; plug opening in throttle body. Connect a hand vacuum pump to open end of vacuum tube and apply 12 in. Hg (300mm Hg), and raise engine speed to 4,000 rpm. Voltage should be above 0.6 volts.
  4.  
  5. Replace oxygen sensor if voltages are out of range.
  6.  



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Fig. Fig. 1: Oxygen sensor testing-1985-87 fuel injected models

Manifold Air Pressure (MAP) Sensor

See Figure 2

1985-87 MODELS
  1. Disconnect the MAP sensor vacuum hose from the throttle body; plug opening in throttle body. Connect a vacuum hand pump to open end of vacuum tube.
  2.  
  3. Unplug the connector from control unit. Install system checker harness (07999-PD6000A or equivalent) between control unit and wire harness connector.
  4.  
  5. Turn ignition switch ON . Connect a digital voltmeter positive probe to C11 terminal of system checker harness and negative probe to C14 terminal. Measure voltage between two terminals. Voltmeter should indicate between 0.5 volts at 4 in. Hg (100mm Hg) of vacuum and 4.5 volts at 45 in. Hg (1200mm Hg).
  6.  
  7. If voltage is incorrect, check vacuum tube for leakage, then check the wires between control unit and sensor for an open or short circuit. Replace sensor if wires are normal.
  8.  



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Fig. Fig. 2: MAP sensor testing-1985-87 fuel injected models

Atmospheric Pressure (PA) Sensor
1985-87 MODELS

See Figure 3

  1. Unplug the connector from the control unit. Install a system checker harness (07999-PD6000A or equivalent) between control unit and wire harness connector.
  2.  
  3. Turn ignition switch ON . Connect a digital voltmeter positive probe to C9 terminal of system checker harness and negative probe to C12 terminal. Measure voltage between two terminals. Voltmeter should indicate 2.76-2.96 volts.
  4.  
  5. If voltage is outside ranges, check for open or short circuit between ECU and PA sensor. Replace PA sensor with a new one if wires are in good condition.
  6.  



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Fig. Fig. 3: ECU connector showing terminals for checking the Atmospheric Pressure (PA) Sensor-1985-87 fuel injected models

Idle Mixture Adjuster (IMA) Sensor
1985-87 MODELS

See Figure 4

  1. Measure resistance between Green terminal and Yellow terminal (Yellow/White and Black terminal on 1987 models) of control box coupler. Resistance should be 250-6200 ohms.
  2.  
  3. Replace IMA sensor if resistance is out of range.
  4.  



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Fig. Fig. 4: Idle mixture adjuster sensor testing-1985-87 fuel injected models

Intake Air Temperature (TA)/Coolant Temperature (TW) Sensor
1985-87 MODELS

See Figures 5 and 6

  1. Unplug the connector and remove TA/TW sensor from inlet manifold/cylinder head.
  2.  
  3. To test a sensor, suspend it in cold water and heat water slowly. Measure resistance between terminals. Measurements should be 9800-13,400 ohms at 95°F (40°C) and 2200-3500 ohms at 176°F (80°C).
  4.  
  5. Replace sensor if resistance is outside of range.
  6.  



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Fig. Fig. 5: Intake air temperature and coolant temperature sensor testing-1985-87 fuel injected models



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Fig. Fig. 6: Disengaging IAT sensor located on the intake manifold-1985-87-style CRX Si shown

Crank Angle Sensor (CYL Sensor)
1985-87 MODELS

See Figure 7

If either CYL or TDC sensor tests bad, replace as an assembly.

  1. Disconnect connector of crank angle sensor.
  2.  
  3. Measure resistance between the white and red wire at the terminal at the sensor. Resistance should be 6,500-8,500 ohms.
  4.  
  5. Measure insulation resistance between the white and red wires at the terminal of the sensor and crank angle sensor housing. Resistance should 100,000 ohms or more.
  6.  



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Fig. Fig. 7: Crank angle sensor testing-1985-87 fuel injected models

Crank Angle Sensor (TDC Sensor)
1985-87 MODELS

See Figure 8

If either CYL or TDC sensor tests bad, replace as an assembly.

  1. Unplug the connector of crank angle sensor.
  2.  
  3. Measure resistance between the brown and red wires at the sensor terminal. Resistance should be 6,500-8,500 ohms.
  4.  
  5. Measure insulation resistance between brown and red wires at the terminal of the sensor and crank angle sensor housing. Resistance should be 100,000 ohms or more.
  6.  



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Fig. Fig. 8: TDC sensor testing-1985-87 fuel injected models

Throttle Angle Sensor
1985-87 MODELS

See Figure 9

Do not adjust the throttle valve stop screw since it is preset at factory.

  1. Unplug the connector of throttle angle sensor.
  2.  
  3. Measure full resistance between Brown/Black terminal and Yellow/Red terminal at sensor. Resistance should be 3,200-7,200 ohms.
  4.  



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Fig. Fig. 9: Throttle angle sensor testing-1985-87 fuel injected models

Idle Control Solenoid Valve
1985-87 MODELS

The idle control solenoid valve is activated by commands from the ECU. When the solenoid valve opens, it allows vacuum in the upper vacuum hose (between the air filter and the solenoid valve) and increases idle speed under the following conditions:



For a short period after starting the engine.
 
Whenever electrical loads are turned on (however the ECU will close the solenoid valve when engine rpm is raised over 1,700 rpm).
 

While the solenoid valve is being activated, 9 volts or more should be available between the Black wire on 1985-86 models (Black/Yellow on 1987 models) connected at the solenoid valve terminal (+) and the Light Green wire on 1985-86 models (Green/White on 1987 models) connected to the negative terminal (-) of the main wire harness at the control box.

  1. Open the control box lid and unplug the 8-pin connector at the wire harness from the control box.
  2.  
  3. Disconnect the vacuum hose between the idle control solenoid valve and the No. 10 vacuum hose (upper vacuum hose of idle control solenoid valve from 3-way joint on 1987-88 models) and connect the vacuum pump to the hose.
  4.  
  5. Apply vacuum to the hose. It should hold vacuum.
  6.  
  7. Connect battery positive terminal to Black terminal of control box and negative battery terminal to Light Green terminal.
  8.  
  9. Apply vacuum to hose. It should not hold vacuum. If vacuum holds, replace solenoid valve.
  10.  

Fast Idle Control Solenoid Valve
1985-87 MODELS

The fast idle control solenoid valve is open when the atmospheric pressure is 26 in. Hg (660mm Hg) or less. Vacuum is produced in the vacuum hose (between the solenoid valve and air filter).

  1. When the valve is open, 9 volts or more should be available for 1985-86 models between the Black terminal (+) and Yellow terminal (-) (Black/Yellow terminal (+) and Green/Yellow terminal (-) on 1987 models) of the main wire harness of the control box.
  2.  
  3. Open the control box lid and unplug the 8-pin connector.
  4.  
  5. Disconnect the lower vacuum hose of the fast idle control solenoid valve from the uppermost hose that connects to the 3-way joint and connect the vacuum pump for testing.
  6.  
  7. Apply vacuum to the hose. It should hold vacuum.
  8.  
  9. Connect the battery positive terminal to the Black terminal of control box coupler, and the battery negative terminal to Yellow terminal.
  10.  
  11. Apply vacuum to the hose. It should not hold vacuum. If the vacuum holds, replace the valve.
  12.  

IDLE SPEED TOO HIGH AFTER WARMUP

See Figures 10, 11, 12 and 13

The fast idle valve is factory adjusted, it should not be disassembled. Check PCV (engine breather) circuit tubing for breakage, disconnection, clogging, etc. Check that the throttle valves are fully closed.



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Fig. Fig. 10: Fast idle valve assembly-1985-87 fuel injected models



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Fig. Fig. 11: If the fast idle valve is found faulty, unbolt the valve from its location on the back of the intake plenum-1985-87 multi-point fuel injected



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Fig. Fig. 12: Once the faulty valve is unbolted, it pulls cleanly away from its mounting point-1985-87 multi-point fuel injected



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Fig. Fig. 13: On all models, if fast idle valve replacement is required, do not re-use the old O-rings-1985-87 multi-point fuel injected shown

  1. Confirm that engine is adequately warmed.
  2.  
  3. Check whether the idling control function is normal.
  4.  
  5. Remove the cover of the fast idle valve.
  6.  
  7. Check that the valve is completely closed. If not, air is being sucked from valve seat area. It can be detected by putting your finger on valve seat area.
  8.  
  9. If any suction sound is felt, the valve is leaking. Replace the fast idle valve and adjust idle speed.
  10.  

IDLE SPEED TOO LOW AFTER WARMUP

Fast idle valve is factory adjusted, it should not be disassembled. Check PCV (engine breather) circuit tubing for breakage, disconnection, clogging, etc. Check that throttle valve are fully closed.

  1. Remove idle adjusting screw.
  2.  
  3. Wash idle adjusting screw and air bypass channel with carburetor cleaner.
  4.  
  5. Readjust the idle speed after cleaning.
  6.  

FAST IDLE SPEED IS LOW WHEN ENGINE IS COLD

The fast idle valve is factory adjusted, it should not be disassembled. Fast idle speed should be 1250-2250 rpm.

  1. Remove fast idle valve assembly from throttle body.
  2.  
  3. Apply cold water and cool down wax part of fast idle valve to 41-86°F (5-30°C).
  4.  
  5. Blow through part A of the fast idle valve, and check that a fairly large amount of air flows without resistance.
  6.  
  7. If the air does not flow or resistance is great, replace the fast idle valve and adjust the idle speed.
  8.  

Dashpot
1985-87 MODELS

See Figure 14

  1. With engine OFF , slowly open throttle arm until dashpot rod is raised up as far as it will go.
  2.  
  3. Release throttle arm and measure time until throttle arm contacts stop screw. Time should be less than 2 seconds.
  4.  
  5. If time is over 2 seconds, replace dashpot check valve.
  6.  
  7. If rod does not operate, check for bound linkage, or for clogged check valve or vacuum line. If OK, replace dashpot.
  8.  



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Fig. Fig. 14: Dashpot system components-1985-87 fuel injected models

Injector Test
1985-87 MODELS

Check following items before testing idle speed, ignition timing, valve clearance and idle CO%.

  1. If engine will run, disconnect injector couplers with engine idling, and inspect change in idling speed. Idle should drop the same for each cylinder.
  2.  
  3. Check clicking sound of each injector by means of a stethoscope when engine is idling.
  4.  
  5. If any injector fails to make a clicking sound, check wiring between ECU and injector. Voltage at injector coupler should fluctuate 0-2 volts. If voltage is OK, replace injector.
  6.  
  7. If engine can not be started, remove coupler of injector, and measure resistance between terminals of injector. Resistance should be 1.5-2.5 ohms.
  8.  
  9. If resistance is not as specified, replace injector. If resistance is normal, check wiring between resistor and injector, wiring between resistors and control unit, and resistors.
  10.  

Fuel System Resistor
1985-87 MODELS

See Figure 15

  1. Disconnect resistor coupler.
  2.  
  3. Check for resistance between each of resistor terminals E, D, C and B and power terminal A . Resistance should be 5-7 ohms.
  4.  
  5. Replace resistor with a new one if any of resistances are outside of specification.
  6.  



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Fig. Fig. 15: Fuel system resistor testing-1985-87 fuel injected models

Main Relay

See Figure 16



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Fig. Fig. 16: Main relay and terminal locations for testing-1985-87 fuel injected models

1985-91 MODELS
  1. Remove the main relay, near under-dash fuse box.
  2.  
  3. Connect battery positive terminal to No. 4 terminal and battery negative terminal to No. 8 terminal of main relay.
  4.  
  5. Check for continuity between No. 5 terminal and No. 7 terminal of main relay. If no continuity, replace main relay.
  6.  
  7. Connect battery positive terminal to No. 5 terminal and battery negative terminal to No. 2 terminal of main relay.
  8.  
  9. Check that there is continuity between No. 1 terminal and No. 3 terminal of main relay. If there is no continuity, replace main relay.
  10.  
  11. Connect battery positive terminal to No. 3 terminal and battery negative terminal to No. 8 terminal of main relay.
  12.  
  13. Check that there is continuity between No. 5 terminal and No. 7 terminal of main relay. If there is no continuity, replace the PGM-FI main relay.
  14.  

PGM-FI Main Relay
1992-95 Models

See Figure 17



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Fig. Fig. 17: PGM-FI relay terminal locations

If the car starts and runs ok, the PGM-FI main relay is good. If you have reason to suspect it is faulty, then perform the following testing procedure:

  1. Remove the relay.
  2.  
  3. Attach the battery positive terminal to the No. 6 terminal and the battery negative terminal to the No. 8 terminal of the PGM-FI main relay.
  4.  
  5. Check for continuity between the No. 5 terminal and No. 7 terminal on the relay. If there is no continuity, replace the relay.
  6.  
  7. If there is continuity, attach the battery positive terminal to the No. 5 terminal and the battery negative terminal to the No. 2 terminal of the PGM-FI main relay.
  8.  
  9. Check for continuity between the No. 1 and No. 3 terminal of the relay. If there is no continuity, replace the relay and re-test beginning with step 1.
  10.  
  11. If there is continuity, attach the battery positive terminal to the No. 3 terminal, and the battery negative terminal to the No. 8 terminal of the relay.
  12.  
  13. Then check that there is continuity between the No. 5 terminal and the No. 7 terminal. If there is no continuity, replace the relay and re-test beginning with step 1. If there is continuity, the relay is ok.
  14.  

Harness
1985-87 MODELS
  1. Keep ignition switch in the OFF position.
  2.  
  3. Unplug the main relay connector.
  4.  
  5. Connect positive probe of circuit tester to Yellow/White in coupler and ground the negative probe of the tester to the body ground. Tester should read battery voltage.
  6.  
  7. If there is no voltage, check wiring between battery and main relay as well as ECU fuse in engine compartment.
  8.  
  9. Connect positive terminal of tester to Black/Yellow wire of coupler and ground negative terminal of tester to body ground.
  10.  
  11. Turn ignition switch ON . Tester should read battery voltage.
  12.  
  13. If no voltage, check wiring from ignition switch and main relay as well as fuse No. 4.
  14.  
  15. Connect positive terminal of tester to Blue/White wire in coupler and ground negative terminal to body.
  16.  
  17. Turn the ignition switch to START position. The tester should read battery voltage.
  18.  
  19. If there is no voltage, check the wiring between the ignition switch and the main relay as well as starter fuse No. 1.
  20.  
  21. Connect a jumper wire between the Yellow/White wire and the Yellow wire for 1985-86 models (Black/Yellow wire on 1987 models) in coupler. The fuel pump should work.
  22.  
  23. If pump does not work, check wiring between battery and fuel pump and wiring from fuel pump to ground (Black wire).
  24.  

1988-91 MODELS
  1. Keep ignition switch in OFF position.
  2.  
  3. Disconnect main relay connector.
  4.  
  5. Check continuity between Black wire in connector and body ground.
  6.  
  7. Connect positive probe of circuit tester to Yellow/Black wire and negative probe of tester to Black wire. Tester should read battery voltage.
  8.  
  9. If there is no voltage, check wiring between battery and main relay as well as ECU (15A) fuse.
  10.  
  11. Connect positive probe of tester to Black/Yellow wire of connector and ground negative probe of tester to Black wire.
  12.  
  13. Turn ignition switch ON . Tester should read battery voltage.
  14.  
  15. If no voltage, check wiring from ignition switch and main relay as well as fuse No. 14.
  16.  
  17. Connect positive probe of tester to Blue/White wire and negative probe to Black wire.
  18.  
  19. Turn ignition switch to START position. Tester should read 10 volts or more.
  20.  
  21. If no voltage, check wiring between ignition switch and main relay as well as No. 2 (10A) fuse.
  22.  
  23. Connect a jumper wire between 2 Black/Yellow wires in connector. Turn ignition switch ON . Fuel pump should run.
  24.  
  25. If pump does not run, check wiring between battery and fuel pump and wiring from fuel pump to ground (Black wire).
  26.  

Throttle Control Diaphragm
1988-91-EXCEPT 1988 CRX SI

See Figures 18 and 19

  1. Start the engine and allow to reach normal operating temperature.
  2.  
  3. Disconnect the No. 6 vacuum line from the dashpot diaphragm and check engine rpm.
  4.  
  5. If engine rpm is higher than 2000-3000 rpm, adjust by bending the tab.
  6.  
  7. If the engine speed does not change, connect a vacuum gauge to the No. 6 hose and check for vacuum.
  8.  
  9. If there is vacuum, replace the diaphragm. If there is no vacuum, check hose for blockage or leakage.
  10.  
  11. Reconnect vacuum hose and adjust idle as needed.
  12.  



Click image to see an enlarged view

Fig. Fig. 18: Throttle control system components-1988-91 fuel injected models



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Fig. Fig. 19: Electric fuel pump assembly, component view-1988-91 fuel injected models

1988 CRX SI
  1. Start the engine and allow to reach normal operating temperature.
  2.  
  3. Disconnect the No. 6 vacuum line from the dashpot diaphragm and check engine rpm.
  4.  
  5. If the engine speed does not change, connect a vacuum gauge to the No. 6 hose and check for vacuum.
  6.  
  7. If there is vacuum, replace the diaphragm. If there is no vacuum, check hose for blockage or leakage.
  8.  
  9. If engine rpm is out of range, inspect the throttle body.
  10.  

 
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