Inspection Procedure 14

Inspection procedure 14: Hesitation, sag, stumble, poor acceleration or surge

COMMENT

- Defective ignition system, abnormal air/fuel ratio, poor compression pressure, etc. are suspected.

TROUBLESHOOTING HINTS (The most likely causes for this case:)

- Malfunction of the fuel pump system.
- Malfunction of the ignition system.
- Poor compression.
- Improper operation of the PCV valve.
- Vacuum leak.
- Clogged air cleaner.
- Clogged exhaust system.
- Malfunction of the TC-SST 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

NOTE:
To protect the TC-SST, the TC-SST-ECU outputs, into the ECM, the request signal to reduce the engine torque according to the operation condition. Based on the signal, the ECM closes the throttle valve, retards the ignition or carries out fuel cut. At that time, the engine output seems to temporarily reduce, but there is no malfunction.

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 connecting 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 Multiport Fuel Injection (MFI).

NO Go to Step 2.

STEP 2. Using scan tool MB991958, read the diagnostic trouble code
(DTC).

NOTE:
When the TC-SST has a malfunction, the TC-SST-ECU might output the request signal of reducing the engine torque in order to protect the TC-SST.

(1)Turn the ignition switch to the "ON" position.

(2)Read the TC-SST-DTC.

(3)Turn the ignition switch to the "LOCK" (OFF) position.

Q. Is the TC-SST-DTC set?

YES Twin Clutch-Sportronic Shift Transmission (TC-SST).
NO Go to Step 3.
STEP 3. Using scan tool MB991958, check actuator test item 1: injector.

(1)Turn the ignition switch to the "ON" position.

(2)Test Reference Table Actuator Test Reference Table.
1. Item 1: Injector.

(3)Turn the ignition switch to the "LOCK" (OFF) position.

Q. Are thy operating properly?

YES Go to Step 4.
NO Repair or replace it. Then confirm that the malfunction symptom is eliminated.
STEP 4. Check the ignition timing.

(1) Testing and Inspection.

Q. Is the ignition timing normal?

YES Go to Step 5.
NO Check for installed conditions of the timing chain. Then confirm that the malfunction symptom is eliminated.
STEP 5. Using scan tool MB991958, check data list and actuator test.

(1)Turn the ignition switch to the "ON" position.

(2)Check the following items in the data list. Refer to Data List Reference Table Data List Reference Table.
2. Item 5: Intake Air Temperature Sensor.

3. Item 6: Engine Coolant Temperature Sensor.

4. Item 11: Accelerator Pedal Position Sensor (main).

5. Item 12: Accelerator Pedal Position Sensor (sub).

6. Item 13: Throttle Position Sensor (main).

7. Item 15: Throttle Position Sensor (sub).

(3)Turn the ignition switch to the "LOCK" (OFF) position.

Q. Are they operating properly?

YES Go to Step 6.
NO Repair or replace it. Then confirm that the malfunction symptom is eliminated.
STEP 6. Check the fuel pressure.

Refer to Fuel Pressure Test Testing and Inspection.

Q. Is the fuel pressure normal?

YES Go to Step 7.
NO Repair or replace it. Then confirm that the malfunction symptom is eliminated.
STEP 7. Check the spark plugs.

Procedures.

Q. Are there any abnormalities?

YES Replace the spark plug. Then confirm that the malfunction symptom is eliminated.
NO Go to Step 8.
STEP 8. Check the ignition coil.

Testing and Inspection.

Q. Are there any abnormalities?

YES Replace the ignition coil. Then confirm that the malfunction symptom is eliminated.
NO Go to Step 9.
STEP 9. Check the positive crankcase ventilation system.

Crankcase Ventilation System Check.

Q. Is the positive crankcase ventilation system?

YES
Check the following items, and repair or replace the defective items.
8. Vacuum leak.
9. Clogged air cleaner.
10. Clogged exhaust system.
11. Check if fuel is contaminated.
12. Check if the injectors are clogged.
13. Check if the foreign materials (water, kerosene, etc.) got into fuel.
Then confirm that the malfunction symptom is eliminated.

NO Repair it. Then confirm that the malfunction symptom is eliminated.