Engine Controls - Basic Diagnostic Procedures: Other Mitsubishi Diamante II

Compression

Check engine mechanical condition with a compression gauge, vacuum gauge, or an engine analyzer. See engine analyzer manual for specific instructions.

Check engine compression with engine at normal operating temperature, all spark plugs removed and throttle wide open. See COMPRESSION SPECIFICATIONS table.

COMPRESSION SPECIFICATIONS

Exhaust System Backpressure

The exhaust system can be tested with a vacuum or pressure gauge. If using a pressure gauge, remove HO2S or air injection check valve (if equipped). Connect a 0-5 psi pressure gauge and run engine at 2500 RPM. If exhaust system backpressure is greater than 2 psi, exhaust system or catalytic converter is plugged.

If using a vacuum gauge, connect vacuum gauge hose to intake manifold vacuum port. Start engine. Observe vacuum gauge. Open throttle part way and hold steady. If vacuum gauge indication slowly drops after stabilizing, inspect exhaust system for restriction.

FUEL SYSTEM

RELIEVING FUEL PRESSURE

1. On Montero and Montero Sport, remove cargo compartment carpet, remove access plate and disconnect fuel pump harness connector. On all other models, remove rear seat cushion, remove access plate (if required) and disconnect fuel pump harness connector.
2. On all models, start engine. Let engine run until it stops. Turn ignition off. Disconnect negative battery cable. Connect fuel pump harness connector. Install rear seat and/or carpet as necessary.

Eclipse 2.0L Non-Turbo

1. Relieve fuel pressure. See «RELIEVING FUEL PRESSURE»(ref-91118-S38905489622001030200000) . Connect fuel pressure gauge to fuel rail service port.
2. Turn ignition on (engine off). Use scan tool to operate fuel pump. Check fuel pressure. See «FUEL PUMP PERFORMANCE»(ref-91118-S09672164472001030200000) table. If fuel pressure is too low, check for clogged fuel filter, pressure regulator leaking or low fuel pump delivery pressure. If fuel pressure is too high, check for bad fuel pressure regulator or clogged fuel return hose.
3. Repeat fuel system test. Check fuel pressure. Turn ignition off. Wait 2 minutes, then check pressure. If pressure drops sharply after ignition is turned off, check for fuel pump check valve stuck open. If fuel pressure drops gradually after ignition is turned off, check for leaky injector or bad pressure regulator.
4. When fuel pressure test is complete, repeat fuel pressure release procedure before disconnecting fuel pressure gauge. Make sure fuel does not leak from service port. Reinstall protective cover.

All Models Except Eclipse 2.0L Non-Turbo

1. Relieve fuel pressure. See «RELIEVING FUEL PRESSURE»(ref-91118-S38905489622001030200000). Disconnect high pressure fuel inlet line at fuel rail. Remove throttle body bracket (if necessary). Connect fuel pressure gauge with adapter between fuel rail and high pressure fuel inlet line. (Scheme 1) Use scan tool to operate fuel pump. Ensure no fuel leaks are present.
2. Start engine and allow it to idle. Measure fuel pressure with vacuum hose connected to fuel pressure regulator. Record fuel pressure reading. See «FUEL PUMP PERFORMANCE»(ref-91118-S09672164472001030200000) table. Disconnect and plug vacuum hose from fuel pressure regulator. Record fuel pressure reading. FUEL PUMP PERFORMANCE Application At Idle w/Vacuum psi (kPa) At Idle w/o Vacuum psi (kPa) Eclipse 2.0L Non-Turbo (1) (1) Turbo 33 (228) 42-45 (290-310) 3000GT Turbo 34 (234) 43-45 (296-310) All Other Models 38 (262) 47-50 (324-345) (1) With key on engine off, pressure should be 47-50 psi (324-345 kPa)
3. Check for fuel pressure in fuel return hose by gently pinching hose while increasing engine speed. If fuel volume is low, fuel pressure in return hose will not be felt. Increase engine speed to 2500-3000 RPM, 2-3 times. Return engine to idle. Fuel pressure should not drop when engine is returned to idle.
4. Turn ignition off. Ensure fuel pressure reading does not decrease within 2 minutes. If a decrease is noted, monitor speed of decrease.
5. If fuel pressure is lower than specification, fuel pressure drops at idle after increasing engine speed to 2500-3000 RPM, or no fuel pressure in fuel return hose can be felt, check for clogged fuel filter, or faulty fuel pressure regulator or fuel pump.
6. If fuel pressure is greater than specification, check for a faulty fuel pressure regulator or plugged fuel return line. If fuel pressure does not change when vacuum hose to regulator is connected or disconnected, check for a leaking or clogged vacuum hose to fuel pressure regulator or faulty fuel pressure regulator.
7. If fuel pressure decreases suddenly after engine is stopped, check valve in fuel pump is not seated. Replace fuel pump. If fuel pressure drops slowly, fuel injector is leaking or fuel pressure regulator valve seat is leaking. Check for faulty fuel injector or fuel pressure regulator. Repair as necessary.
8. When fuel pressure test is complete, repeat fuel pressure release procedure before disconnecting fuel pressure gauge. Install NEW "O" ring at end of high pressure fuel inlet line. Check for fuel leaks.

Scheme 1

MFI CONTROL RELAY

MFI control relay switches power to vehicle sensors and actuators including Volume Airflow (VAF) sensor, crankshaft position sensor, idle speed control, injectors and fuel pump. When ignition switch is turned to RUN position, PCM energizes coils controlling injectors, VAF sensor and idle air control. When ignition switch is turned to START position, PCM energizes coils (through park/neutral position switch on A/T models) to supply power to fuel pump. Relay failure will cause a no-start condition.

Remove MFI (ASD) relay. Check resistance between relay terminals No. 4 and 6. Resistance should be 35-75 ohms. Connect jumper wire between battery positive terminal and relay terminal No. 6. Connect second jumper wire between battery negative terminal and MFI relay terminal No. 4. With relay energized, continuity should exist between terminals No. 2 and 8. With power source removed, continuity should not exist between terminals No. 2 and 8. If relay does not test as specified, replace MFI relay.

All Except Eclipse 2.0L Non-Turbo

Remove MFI/fuel pump relay. Check resistance between relay terminals No. 2 and 4. Resistance should be about 70 ohms. Connect jumper wire between battery positive terminal and relay terminal No. 4. Connect second jumper wire between battery negative terminal and MFI relay terminal No. 2. With relay energized, continuity should exist between terminals No. 1 and 3. With power source removed, continuity should not exist between terminals No. 1 and 3. If relay does not test as specified, replace MFI relay.

IGNITION CHECKS

Note. Perform all circuit tests with a Digital Volt-Ohmmeter (DVOM) with a minimum 10-megohm input impedance, unless stated otherwise in test procedure.

SPARK

Check for spark at coil wire (if applicable) and at each spark plug wire using a high output spark tester. Check spark plug wire resistance on suspect wires. Wire resistance should not exceed 22,000 ohms for all models except Eclipse 2.0L non-turbo and Montero. On Eclipse 2.0L non-turbo, resistance should not exceed 8000 ohms. On Montero, resistance should not exceed 26,000 ohms.

CAMSHAFT POSITION (CMP) SENSOR

For CMP sensor testing procedure, see appropriate SELF-DIAGNOSTICS article.

CRANKSHAFT POSITION (CKP) SENSOR

For CKP sensor testing procedure, see appropriate SELF-DIAGNOSTICS article.

Ignition Coil Resistance (Eclipse)

1. On Eclipse 2.0L non-turbo, go to step 3. On Eclipse 2.0L turbo and 2.4L, disconnect ignition coil connector. Go to next step.
2. On Eclipse 2.0L turbo, use DVOM to measure primary coil resistance between ignition coil connector terminals No. 2 and 3 (coil for cylinders No. 1 and 4) and terminals No. 1 and 3 (coil for cylinders No. 2 and 3). (Scheme 2)or (Scheme 3). On Eclipse 2.4L, use DVOM to measure primary coil resistance between ignition coil terminals. Go to step 4.
3. Disconnect ignition coil connector. Using DVOM, measure primary coil resistance at coil (component side) 3-pin connector. Measure between center and right terminals of connector for cylinders No. 1 and 4, and between center and left terminals of connector for cylinders No. 2 and 3.
4. On all models, remove ignition wires from coil. Measure secondary coil resistance between coil towers for cylinders No. 1 and 4 and between coil towers for cylinders No. 2 and 3. Primary and secondary coil resistance should be within specification. See «ECLIPSE IGNITION COIL RESISTANCE»(ref-91118-S13707376462001030200000) table. Connect coil harness connector. Connect ignition wires to coil. ECLIPSE IGNITION COIL RESISTANCE - Ohms @ 68°F (20°C) Application Primary Secondary 2.0L Non-Turbo.51-.61 11,500-13,500 Turbo.70-.86 11,300-15,300 2.4L.74-.90 20,100-27,300

Scheme 2

Scheme 3

Ignition Coil With Built-In Power Transistor Resistance (Galant 2.4L & Mirage 1.8L)

1. Remove coils. Check resistance between high voltage terminals of each coil. On Galant 2.4L, resistance should be 15300-20700 ohms. On Mirage 1.8L, resistance should be 14000-21000 ohms.
2. Using a 1.5-volt dry cell battery, connect negative end of battery to coil terminal No. 2 and positive end to coil terminal No. 3. (Scheme 4)
3. Using an analog ohmmeter, check for continuity between coil terminals No. 1 and 2. Continuity should exist. With positive end of 1.5-volt battery disconnected, there should be no continuity. Replace coil if it fails test.

Scheme 4

Ignition Failure Sensor (Galant 2.4L & Mirage 1.8L)

Using analog ohmmeter, check resistance between ignition failure sensor terminals No. 3 and 4. (Scheme 5) Resistance should be.1 ohm or less.

Scheme 5

Power Transistor (Eclipse Turbo & 2.4L)

1. To test the section of the power transistor that controls cylinders No. 1 and 4, disconnect power transistor connector. Using a 1.5-volt dry cell battery, connect negative end of battery to terminal No. 3 of power transistor and positive end to terminal No. 7. (Scheme 6)
2. Using an analog ohmmeter, check for continuity between terminals No. 3 and 8 of power transistor. Continuity should exist. With positive end of 1.5-volt battery disconnected, there should be no continuity. Replace power transistor if it fails test.
3. To test the section of the power transistor that controls cylinders No. 2 and 3, connect negative end of 1.5-volt dry cell battery to terminal No. 3 of power transistor and positive end to terminal No. 2.
4. Using an analog ohmmeter, check for continuity between terminals No. 1 and 3 of power transistor. Continuity should exist. With positive end of 1.5-volt battery disconnected, there should be no continuity. Replace power transistor if it fails test.

Scheme 6

Ignition Coil Resistance

1. On 3000GT DOHC, go to next step. On Montero and Montero Sport, use DVOM to measure primary coil resistance between each individual coil. To check secondary coil resistance, measure resistance between towers of each individual coil. Replace coil if primary and secondary coil resistances are not within specification. See «IGNITION COIL RESISTANCE (V6)»(ref-91118-S39445478722001030200000) table. IGNITION COIL RESISTANCE (V6) - Ohms @ 68°F (20°C) Application Primary Secondary 3.0L VIN H.74-.90 20,100-27,300 VIN J & K.67-.81 11,300-15,300 3.5L (VIN R).74-90 20,100-27,300
2. Using DVOM, measure primary coil resistance between terminal No. 3 (power terminal) and each individual coil terminal. (Scheme 7) Terminal No. 1 controls coil "B", terminal No. 2 controls coil "A", and terminal No. 4 controls coil "C". (Scheme 8) To check secondary coil resistance, measure resistance between towers of each individual coil. Replace coil if primary and secondary coil resistances are not within specification. See «IGNITION COIL RESISTANCE (V6)»(ref-91118-S39445478722001030200000) table.

Scheme 7

Scheme 8

Power Transistor

1. To test section of power transistor that controls cylinders No. 1 and 4 of ignition coil, disconnect power transistor connector. Using a 1.5-volt dry cell battery, connect negative end of 1.5-volt battery to terminal No. 4 of power transistor and positive end to terminal No. 3. (Scheme 9)
2. Using an analog ohmmeter, check for continuity between terminals No. 4 and 13 of power transistor. Continuity should exist. With positive end of 1.5-volt battery disconnected, there should be no continuity. Replace power transistor if it fails test.
3. To test section of power transistor that controls cylinders No. 2 and 5 of ignition coil, connect negative end of 1.5-volt battery to terminal No. 4 of power transistor and positive end to terminal No. 2.
4. Using an analog ohmmeter, check for continuity between terminals No. 4 and 12 of power transistor. Continuity should exist. With positive end of 1.5-volt battery disconnected, there should be no continuity. Replace power transistor if it fails test.
5. To test section of power transistor that controls cylinders No. 3 and 6 of ignition coil, connect negative end of 1.5-volt battery to terminal No. 4 of power transistor and positive end to terminal No. 1.
6. Using an analog ohmmeter, check for continuity between terminals No. 4 and 11 of power transistor. Continuity should exist. With positive end of 1.5-volt battery disconnected, there should be no continuity. Replace power transistor if it fails test.

Scheme 9

Using a DVOM, measure primary coil resistance between specified coil terminals. (Scheme 10)- (Scheme 11). On Galant, measure between distributor connector terminals No. 1 and 2. On Mirage, measure between distributor connector terminals No. 1 and 2. On Diamante, measure between distributor connector terminals No. 1 and 4. On all other vehicles, measure between positive and negative terminals. On Galant and Mirage, measure secondary coil resistance between terminal No. 1 and ignition coil tower. On all other vehicles, measure secondary coil resistance between coil positive terminal and ignition coil tower. Primary and secondary coil resistance should be within specification. See IGNITION COIL RESISTANCE table.

IGNITION COIL RESISTANCE - Ohms @ 68°F (20°C)

Scheme 10

Scheme 11

Power Transistor (Diamante)

1. Disconnect distributor connector. Using a 1.5-volt dry cell battery, connect negative end of 1.5-volt battery to terminal No. 4 of power transistor and positive end to terminal No. 3. (Scheme 10)
2. Using an analog ohmmeter, check for continuity between terminals No. 1 and 4 of power transistor. Continuity should exist. With positive end of 1.5-volt battery disconnected, there should be no continuity. Replace power transistor if it fails test.

Power Transistor (Galant 3.0L)

1. Disconnect distributor connector. Using a 1.5-volt dry cell battery, connect negative end of 1.5-volt battery to distributor connector terminal No. 4 and positive end to distributor connector terminal No. 3. (Scheme 10)
2. Using an analog ohmmeter, check for continuity between distributor connector terminals No. 2 and 3. Continuity should exist. With positive end of 1.5-volt battery disconnected, there should be no continuity. Replace power transistor if it fails test.

Power Transistor (Mirage)

1. Disconnect power transistor (distributor) connector. Using a 1.5-volt dry cell battery, connect negative end of 1.5-volt battery to terminal No. 4 of power transistor and positive end to terminal No. 3. (Scheme 12)
2. Using an analog ohmmeter, check for continuity between terminals No. 2 and 4 of power transistor. Continuity should exist. With positive end of 1.5-volt battery disconnected, there should be no continuity. Replace power transistor if it fails test.

Scheme 12

Power Transistor (Montero Sport 2.4L & 3000GT SOHC)

1. Disconnect power transistor connector. Using a 1.5-volt dry cell battery, connect negative end of 1.5-volt battery to terminal No. 2 of power transistor and positive end to terminal No. 1. (Scheme 13)
2. Using an analog ohmmeter, check for continuity between terminals No. 2 and 3 of power transistor. Continuity should exist. With positive end of 1.5-volt battery disconnected, there should be no continuity. Replace power transistor if it fails test.

Scheme 13

IDLE SPEED & IGNITION TIMING

Ensure idle speed and ignition timing are set to specification. See IGNITION TIMING SPECIFICATIONS table. For adjustment procedures, see ON-VEHICLE ADJUSTMENTS article.

IGNITION TIMING SPECIFICATIONS (Degrees BTDC @ RPM)

SUMMARY

If no faults were found while performing BASIC DIAGNOSTIC PROCEDURES, proceed to appropriate SELF-DIAGNOSTICS article. If no Diagnostic Trouble Codes (DTCs) are found in self-diagnostics, proceed to TROUBLE SHOOTING - NO CODES article for diagnosis by symptom (i.e., ROUGH IDLE, NO START, etc.) or intermittent diagnostic procedures.