69

j. Poor intake and exhaust valve seal, failed piston ring, low compression pressure;

h. Too many carbon deposit in spark plug and combustion chamber;

k. Water temperature switch and thermostat fault;

l. Aging of Oxygon sensor;

m. Incorrect ignition timing;

n. Check valve fault.

Figure 149

Engine is difficult to start

 
 
Check whether the air cleaner is clogged      

Clogged     

Troubleshooting

 
 OK

Check the idle control valve 

NG

 

  Repair or replace 

 OK

Check the fuel pressure          

Excessivly low

      Service the electric fuel pump, 

 

 

 

 

 

        fuel filter and fuel pressure regulator

 OK

Check the vacuum pressure sensor         

NG

              Replace

 OK

Check the water temperature sensor and intake air temperature sensor          

NG         

Replace 

 OK

Check the start switch signal        

No        

Service the start signal wire

 OK

Check the ignition timing         

Misaligned      

Adjust

 OK

Check the cylinder pressure 

  

NG

 

       Disassemble the engine

 OK

Replace the ECU to retry

70

(3) Diagnosis procedure for insufficient engine power (Figure 150)

2. Poor deceleration

(1)  Symptom

Idling is normal, but the engine is frequently turned off upon sudden release of the accelerator pedal

during driving.

(2) Causes and Troubleshooting:

a. Throttle position sensor is damaged and shall be replaced;

b. Initial idling is not properly adjusted or automatic idle control is wrong, fuel cut RPM is too low,

ECU fault, repair or replace them.

Insufficient power

 Insufficient 

Check whether throttle valve can be fully open      

Unable to be fully open   

Adjust

 
 OK

Check whether the air cleaner is clogged 

      

Clogged

 

  Clean or replace

 OK

Check the throttle valve position sensor for failure 

Abnormal

 

Repair or replace

 OK

Check the water temperature switch and thermostat 

NG

  

Replace

 OK

Check the vacuum pressure sensor for failure 

NG

 

       Replace

 OK

Check the fuel pressure    

Excessively low or high

  Service the electric fuel pump, 

       fuel 

filter 

and 

fuel 

pressure 

regulator

 OK

Check the oxygen sensor   

Incorrect         

Replace

 OK

Check the injector 

 

Incorrect          

Replace

 OK

Replace the spark plug, ignition coil and high voltage wire

 OK

Disassemble the engine

Figure 150

71

3. Poor acceleration

(1) Symptom

Engine speed can not be increased immediately after depressing the accelerator pedal, there is 

time lag,and the acceleration reaction is delayed or there is slight fluctuation during the acceleration.

(2) Causes and Troubleshooting

a. There is fault in throttle position sensor, repair or replace it;

b. Poor intake system seal, repair it;

c. There is low fuel pressure, troubleshoot it;

d. Poor injector operation, clean or replace it;

e. Intake pressure temperature sensor fault, repair or replace it;

f. Check valve is damaged and shall be replaced;

g. Ignition advance angle is not correct and shall be adjusted;

h. Fuel pressure regulator is damaged and shall be replaced;

i. Air cleaner is clogged and shall be cleaned or replaced;

(3) Diagnosis procedure for poor acceleration (Figure 151)

Figure 151

Poor acceleration

 
 
Check the air tightness of the intake air system      

Poor seal        

Repair

 
 OK

Check whether the air cleaner is clogged  

      

Clogged

 

  Clean or replace

 OK

Check the throttle valve position sensor for failure 

Abnormal

 

Repair or replace

 OK

Check the fuel pressure           

Abnormal        

Service the electric fuel pump, 

 

 

 

 

 

   fuel filter and fuel pressure regulator

 OK

Check whether the injector inject properly 
at idle and maximum load  

 

        

NG

         Replace

 OK

Check whether the check valve and EVAP are faulty       

Yes          

Repair or replace

 OK

Check whether the vacuum pressure sensor is OK 

NG

 

  Replace

 OK

Adjust  a ECU to retry

72

4.  Big fuel consumption

(1) Symptom:

Engine power is ok, but the fuel consumption is big, exhaust pipe discharges black smoke.

(2) Causes and Troubleshooting:

a. When idling, idle speed is high and shall be adjusted;

b. Water temperature sensor fault, service or replace it;

c. Water temperature switch and thermostat fault, repair or replace it;

d. Oxygen sensor fault, repair or replace it;

e. Fuel pressure is big and shall be adjusted;

f. Injector fault (fuel leakage), repair or replace it;

g. Throttle position sensor fault, repair or replace it;

h. Fuel pressure regulator is damaged and shall be replaced;

i. Intake pressure temperature sensor fault, repair or replace it.

5. Unstable idle, liable to be turned off

(1) Symptom:

Engine starts normally, but the idle is unstable regardless of cold or hot status, idle speed is too low and

the engine is liable to be turned off.

(2) Causes and Troubleshooting

a. Poor idle control valve operation, repair or replace it;

b. Low idle speed and faulty or improperly adjusted idle control valve, troubleshoot it;

c. Water temperature sensor fault, repair or replace it;

d. Poor intake system seal, need to be repaired;

e. High voltage spark is too weak, spark plug carbon deposit or electrode clearance is too small, need

to be repaired, cleared and adjusted;

f. Pressure sensor fault, repair or replace it;

g. The compression pressure in the cylinder is too low, need to be serviced;

h. Fuel line pressure is too low, needed to be serviced;

i. Air cleaner is clogged, clean or replace it;

j. Poor injector atomization, fuel leakage, block or big injection variation, need to be repaired;

(3) Diagnosis procedure (Figure 152)

6. Unstable idle at cold status,  liable to be turned off

(1) Symptom

During the cold start, idle is unstable and engine is liable to be turned off, the normal idle is recovered

after warming of the engine.

(2) Causes and Troubleshooting

a. Water temperature sensor fault, repair or replace it;

b. idle control valve fault, repair or replace it.