Mitsubishi Lancer Evolution X. Manual — part 421
MULTIPORT FUEL INJECTION (MFI) DIAGNOSIS
TSB Revision
MULTIPORT FUEL INJECTION (MFI)
13A-749
Inspection procedure 17: Too high CO and HC concentration when idling
.
COMMENT
• Abnormal air/fuel ratio is suspected.
.
TROUBLESHOOTING HINTS (The most
likely causes for this case:)
• Malfunction of the fuel pump system.
• Malfunction of the heated oxygen sensor.
• Malfunction of the ignition system.
• Poor compression.
• Improper operation of the PCV valve.
• Malfunction of the evaporative emission control
system.
• Malfunction of the ECM.
DIAGNOSIS
Required Special Tools:
• MB991958: Scan Tool (M.U.T.-III Sub Assembly)
• MB991824: V.C.I.
• MB991827: USB Cable
• MB991910: Main Harness A
STEP 1. Using scan tool MB991958, read the diagnostic
trouble code (DTC).
CAUTION
To prevent damage to scan tool MB991958, always turn the
ignition switch to the "LOCK" (OFF) position before con-
necting or disconnecting scan tool MB991958.
(1) Connect scan tool MB991958 to the data link connector.
(2) Turn the ignition switch to the "ON" position.
(3) Read the DTC.
(4) Turn the ignition switch to the "LOCK" (OFF) position.
Q: Is any DTC set?
YES : Refer to Diagnostic Trouble Code Chart
.
NO : Go to Step 2.
STEP 2. Check the ignition timing.
Refer to GROUP 11A, On-vehicle Service − Ignition Timing
Check
.
Q: Is the ignition timing normal?
YES : Go to Step 3.
NO : Check for installed conditions of the timing chain.
Then confirm that the malfunction symptom is
eliminated.
AC608435
Data link connector
MB991827
MB991824
MB991910
AB
MULTIPORT FUEL INJECTION (MFI) DIAGNOSIS
TSB Revision
MULTIPORT FUEL INJECTION (MFI)
13A-750
STEP 3. Using scan tool MB991958, check data list.
(1) Turn the ignition switch to the "ON" position.
(2) Check the following items in the data list. Refer to Data List
.
a. Item 5: Intake Air Temperature Sensor.
b. Item 6: Engine Coolant Temperature Sensor.
c. Item AC: Heated Oxygen Sensor (front).
d. Item AD: Heated Oxygen Sensor (rear).
(3) Turn the ignition switch to the "LOCK" (OFF) position.
Q: Are they operating properly?
YES : Go to Step 4.
NO : Repair or replace it. Then confirm that the malfunction
symptom is eliminated.
STEP 4. Check the fuel pressure.
Refer to Fuel Pressure Test
.
Q: Is the fuel pressure normal?
YES : Go to Step 5.
NO : Repair or replace it. Then confirm that the malfunction
symptom is eliminated.
STEP 5. Check the spark plugs.
Refer to GROUP 16, Ignition System − On-vehicle Service −
Spark Plug Check And Cleaning
.
Q: Are there any abnormalities?
YES : Replace the spark plug. Then confirm that the
malfunction symptom is eliminated.
NO : Go to Step 6.
STEP 6. Check the ignition coil.
Refer to GROUP 16, Ignition System − On-vehicle Service −
.
Q: Are there any abnormalities?
YES : Replace the ignition coil. Then confirm that the
malfunction symptom is eliminated.
NO : Go to Step 7.
STEP 7. Check the compression pressure.
Refer to GROUP 11A, On-vehicle Service − Compression Pres-
.
Q: Is the compression pressure normal?
YES : Go to Step 8.
NO : Repair it. Then confirm that the malfunction symptom
is eliminated.
MULTIPORT FUEL INJECTION (MFI) DIAGNOSIS
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MULTIPORT FUEL INJECTION (MFI)
13A-751
STEP 8. Check the positive crankcase ventilation system.
Refer to GROUP 17, Emission Control − Positive Crankcase
Ventilation System − Positive Crankcase Ventilation System
Check
.
Q: Is the positive crankcase ventilation system?
YES : Go to Step 9.
NO : Repair it. Then confirm that the malfunction symptom
is eliminated.
STEP 9. Check the evaporative emission control system.
Refer to GROUP 17, Emission Control − Evaporative Emission
Control System − Purge Control System Check (Purge Flow
Check)
Q: Is the purge control system normal?
YES : Check the following items, and repair or replace the
defective items.
a. Check if the injectors are clogged.
Then confirm that the malfunction symptom is
eliminated.
NO : Repair it. Then confirm that the malfunction symptom
is eliminated.
Inspection procedure 18: Transient, mass emission tailpipe test failure
.
COMMENT
• The test is failed when the air/fuel ratio is not con-
trolled to the ideal air/fuel ratio. This occurs due
to the feedback control by heated oxygen sensor
signals, or deteriorated catalyst.
NOTE: If the three-way catalyst temperature is low
when checking the exhaust gas, the three-way cata-
lyst cannot sufficiently clean the emissions. Warm up
the engine sufficiently before checking the exhaust,
and check immediately.
.
TROUBLESHOOTING HINTS (The most
likely causes for this case:)
• Malfunction of air/fuel ratio control system.
• Malfunction of the fuel pump system.
• Malfunction of the ignition system.
• Poor compression.
• Improper operation of the PCV valve
• Malfunction of the evaporative emission control
system
• Deteriorated catalyst.
DIAGNOSIS
Required Special Tools:
• MB991958: Scan Tool (M.U.T.-III Sub Assembly)
• MB991824: V.C.I.
• MB991827: USB Cable
• MB991910: Main Harness A
STEP 1. Check the exhaust gas with the engine at normal
operating temperature.
Q: Was the exhaust gas checked with engine warmed
sufficiently?
YES : Go to Step 2.
NO : Check it again after enough warm up.
MULTIPORT FUEL INJECTION (MFI) DIAGNOSIS
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MULTIPORT FUEL INJECTION (MFI)
13A-752
STEP 2. Check the following items.
(1) Check the following items.
a. Check all vacuum hoses and connectors.
b. Check electrical wires and connectors for obvious prob-
lems.
Q: Are they normal?
YES : Go to Step 3.
NO : Repair or replace it. Then confirm that the malfunction
symptom is eliminated.
STEP 3. Check the driveability.
Q: Is the driveability normal?
YES : Go to Step 4.
NO : Refer to Trouble Symptom Chart
.
STEP 4. Using scan tool MB991958, read the diagnostic
trouble code (DTC).
CAUTION
To prevent damage to scan tool MB991958, always turn the
ignition switch to the "LOCK" (OFF) position before con-
necting or disconnecting scan tool MB991958.
(1) Connect scan tool MB991958 to the data link connector.
(2) Turn the ignition switch to the "ON" position.
(3) Read the DTC.
(4) Turn the ignition switch to the "LOCK" (OFF) position.
Q: Is any DTC set?
YES : Refer to Diagnostic Trouble Code Chart
.
NO : Go to Step 5.
STEP 5. Check the ignition timing.
Refer to GROUP 11A, On-vehicle Service − Ignition Timing
Check
.
Q: Is the ignition timing normal?
YES : Go to Step 6.
NO : Check that the crankshaft position sensor and timing
chain case are in the correct position. Then confirm
that the malfunction symptom is eliminated.
AC608435
Data link connector
MB991827
MB991824
MB991910
AB
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