17 

 

No. 009 Low idle speed during engine heating in cold condition   

Malfunction Cause 

Solution 

Weak ignition spark 

Check ignition coil, wire and spark plug, whether they are normal. Adjust or 
replace them when necessary. 

Crankcase venting 
device fails 

Check PCV valve, whether it is normal. Replace crankcase venting device when 
necessary. 

Intake system leaking 

Measure vacuum, check the connecting condition of manifold gasket, throttle 
gasket, and all vacuum pipes. 

Thermostat malfunction 

Check thermostat, whether it is leaking, which results warm-up period over 
normal value. Replace thermostat when necessary. 

Idle speed valve 
(steeping motor) 
maladjustment 

Measure the resistance (UAES idle speed valve 17.6Ω, Delphi motor 53Ω, 
Polarsun motor 48±2.4Ω) and voltage of idle motor, whether they are normal. 
Check idle speed motor, whether it is dirty and stuck. Maintain and replace it 
when necessary. 

Improper valve 
clearance 

Adjust valve clearance: on 4-cylinder engine, the intake valve clearance shall 
be 0.20±0.05 mm, the exhaust valve clearance shall be 0.30±0.05mm. On 
3-cylinder engine, the intake/exhaust valve clearance shall be 0.20±0.05mm 
when warming-up, and 0.12±0.04mm in cold condition. 

Low cylinder pressure 

Check engine compression ratio and pressure, whether they are in accordance 
with standard value. 479Q 9.3: 1/1250kpa/250r/min; 479QA 9.8: 
1/1440kpa/250r/min; 481Q 9.4: 1/1360kpa/250r/min; JI376QE 9.5: 
1/1225kpa/350r/min; JL378QE 9.5: 1 / 1225kpa/350r/min; Inspemction the 
cause, whether valve leaking or piston ring and cylinder wearing. Disassembly 
and maintain the engine when necessary. 

Water temperature 
sensor damaged 

Check the resistance of water temperature sensor in cold condition (UAES 
2.5kΩ, at 20 ; Delphi 3.56~2.26kΩ, at 20~30 ; Polarsun 2.5kΩ, at 20 ), 

℃

℃

℃

whether they are in accordance with standard. Or measure the temperature of 
cold vehicle by scanner, whether it is in accordance with actual engine 
temperature. Replace coolant fluid temperature sensor when necessary. 

Injector malfunction 

Check injector, whether it is blocked or stuck. Check atomization and implement 
leak test. Clean or replace injector. 

Oxygen sensor 
malfunction 

Check heat-type oxygen sensor heater resistance (UAES 1~6Ω, Delphi 12Ω, 
Polarsun 13.2Ω±10%), as well as heater voltage, 12V, and signal voltage, 
0.1~0.9V, whether they are in normal range. Check sensor surface, whether it is 
dirty and results voltage over normal value, as well as the fuel-air mixture is too 
thin. 

Ignition timing 
maladjustment 

Check ignition time and calibrate ignition timing, in idle condition: on 4-cylinder 
engine, the ignition advance angle shall be 10°~12° before top dead center. On 
3-cylinder engine, the value shall be 12°±3.75° before top dead center. 

Low idle speed 
during engine 
heating in cold 
condition 

ECU malfunction 

Check connecting conditions of ECU and all wires. 

 

 
 

 

 

18 

 

Low idle speed during engine heating in cold 

condition 

Weak ignition spark 

Crankcase venting device failure 

Water temperature sensor damaged 

Thermostat failure 

Improper valve clearance 

Intake system leaking 

Ignition timing maladjustment 

Low cylinder pressure 

Idle speed valve (steeping motor) 

maladjustment

Injector failure 

Oxygen sensor malfunction 

ECU malfunction 

Adjust 

Replace 

Check 

Check and replace 

Replace 

Replace 

Replace 

Check 

Check 

Clean and replace 

Check 

Clean and replace 

Abnormal 

Abnormal 

Abnormal 

Abnormal 

Low 

Abnormal 

Abnormal 

Abnormal 

Abnormal 

Damaged 

Abnormal 

Abnormal 

Normal 

Normal 

Normal 

Normal 

Normal 

Normal 

Normal 

Normal 

Normal 

Normal 

Normal 

 
 

 

 

19 

 

  No. 010 Canister oil leaking   

Malfunction Cause 

Solution 

Check valve damage, on fuel tank 

Check the single check valve on fuel tank, whether it is damaged. 
Replace fuel tank assembly when necessary. 

Fuel tank cover damage 

Check the single check valve of fuel tank cover, whether it can open. 
Replace fuel tank cover when necessary. 

Canister venting (air) pipe blocked 

Check the white venting pipe, to air, at the bottom of canister, whether it 
is blocked by silt and result oil leaking. Unplug or replace it when 
necessary. 

Controlling canister malfunction 

Check controlling canister inner charcoal and pipe export, whether they 
are blocked. Replace them when necessary. Check canister, whether 
the mounting position is too low. Adjust the mounting height when 
necessary. 

Vacuum pipe blocked, on top of 
canister 

Raise engine speed to 2000r/min, if vacuum pipe suction is low, then 
shall check vacuum pipe system. 

Canister control valve malfunction 

Check canister controlling valve resistance, which shall be 22~30Ω at 
20 . Check controlling wire and valve element, whether they are in 

℃

normal condition. Maintain and replace them when stuck. 

There is fuel 
under 
vehichle 
when 
parking, and 
the engine 
speed is 
unstable 
when idling. 

ECU malfunction 

Check ECU and canister electromagnetic valve controlling circuit, 
whether they are in normal condition. 

 

 

Canister oil leaking 

Check valve damage, on fuel tank 

Fuel tank cover damage 

Controlling canister malfunction 

Pipe blocked, on top of canister 

Canister control valve malfunction 

ECU malfunction 

Replace 

Replace 

Replace 

Replace 

Check 

Replace 

Abnormal 

Damaged 

Blocked 

Damaged 

Damaged 

Damaged 

Normal 

Normal 

Normal 

Normal 

Normal 

 
 

 

 

20 

 

No. 011 Fuel smells in vehicle   

Malfunction Cause 

Solution 

Gas station man-made malfunction 

When filling, fuel dropped around tank filling port and cover, then flows 
into vehicle. Clean vehicle. 

Fuel tank filling port and port cover 
leaking 

Check or replace fuel tank filling port and cover. 

Fuel pipe leak 

Check or replace leaking fuel pipe. 

Fuel tank cracked and leaking 

Check fuel tank, whether it is leaking. Replace it when necessary. 

Canister leak 

Check canister controlling system and venting system. 

Fuel tank inner pressure abnormal 

Replace fuel tank, check valve and fuel filling port cover etc. 

Controlling canister pipe malfunction

Check canister pipe, whether it is dropped. 

Canister controlling valve 
malfunction 

Check canister controlling valve, whether it is blocked, as well as the 
suction capacity, whether it is poor or fails to open. 

Fuel pump and fuel sensor mounting
gasket leaking 

Check or replace fuel pump and fuel sensor mounting sealing. 

Ignition timing maladjustment 

Maintain ignition timing, whether it is delayed. 

Injector leak 

Check sealing of injector and pipe. 

Engine operates abnormal 

Check engine operation, whether there is unavailable cylinder. 

Fuel smells 
in vehicle, 
when 
opening 
window, it 
smells even 
worse 

Oxygen sensor 

Measure the voltage of sensor, whether it is too low, as well as the 
fuel-air ratio, whether it is over normal value.