Symptoms - Engine Controls (LDD or LUJ)
Diagnostic Instructions
Symptoms Description
Symptoms cover conditions that are not covered by DTCs. Certain
conditions can cause multiple symptoms. These conditions are listed
together under Symptoms Testing. Conditions that may only cause
specific symptoms are listed separately under additional symptoms
testing. Perform the symptoms testing before using the additional
symptoms testing.
Symptoms Definition
Backfire: Fuel ignites in the intake manifold
or in the exhaust system, making a loud popping noise. |
Cuts Out, Misses: A steady pulsation or
jerking that follows engine speed, which is usually more pronounced
as the engine load increases. This condition is not normally felt
above 1 500 RPM or 48 km/h (30 MPH). The exhaust has a steady
spitting sound at idle or at low speed. |
Detonation/Spark Knock: A mild to severe ping
which usually gets worse while under acceleration. The engine makes
sharp metallic knocks that change with throttle opening. |
Dieseling, Run-On: Fuel ignites in the intake
manifold or in the exhaust system, making a loud popping
noise. |
Hard Start: Engine cranks OK, but does not
start for a long time. The vehicle does eventually run, or may
start but immediately stalls. |
Hesitation, Sag, Stumble: Momentary lack of
response as the accelerator is pushed down. This condition can
occur at any vehicle speed. This condition is usually more
pronounced when first trying to make the vehicle move, as from a
stop. This condition may cause the engine to stall in severe
conditions. |
Lack of Power, Sluggishness, or Sponginess:
The engine delivers less than expected power. Little or no increase
in speed when the accelerator pedal is pushed down part way. |
Poor Fuel Economy: Fuel economy, as measured
by an actual road test, is noticeably lower than expected. Also,
the fuel economy is noticeably lower than it was on this vehicle at
one time, as previously shown by an actual road test. |
Poor Fuel Fill Quality: Difficulty when
refueling the vehicle. |
Rough, Unstable, or Incorrect Idle and
Stalling: The engine runs unevenly at idle. If severe, the
engine or the vehicle may shake. Engine idle may vary in speed.
Either condition may be severe enough to stall the engine. |
Surges/Chuggles: Engine power variation under
steady throttle or cruise. Feels like the vehicle speeds up and
slows down with no change in the accelerator pedal position. |
Symptoms Verification
• |
The engine control module
(ECM) and the malfunction indicator lamp (MIL) are operating
correctly. |
• |
There are no DTCs
stored. |
• |
The scan tool data is within
the normal operating range. |
• |
Bulletins are not available
for the current symptom. |
• |
The ECM grounds are clean,
tight, and in the correct locations. |
• |
The vehicle tires are
correctly inflated and meet original equipment
specifications. |
• |
The air filter element is not
restricted. |
Symptoms Testing
1. |
Test for the following
conditions: |
|
• |
For the correct installation
of the Mass Air Flow (MAF)/Intake Air Temperature (IAT)
Sensor. |
|
• |
The fuel system for the
following: |
|
• |
The ignition system for the
following: |
|
|
- |
For diagnosis of coolant or oil fouled spark plugs. |
|
|
- |
Wet down the secondary ignition system with water from a spray
bottle. Wetting down the secondary ignition system may help locate
damaged or deteriorated components. Look/listen for arcing or
misfiring as the water is applied. |
|
• |
The operation of the
transmission torque converter clutch (TCC). The scan tool should
indicate an engine speed drop when the TCC is commanded ON.
|
|
• |
The operation of the A/C
compressor. |
|
• |
The crankshaft position sensor
for the correct resistance. The crankshaft position sensor
resistance may be out of range after a hot soak. The resistance
should be between 700-1 200 Ω. |
|
|
- |
Excessive oil in the combustion chamber or leaking valve
seals |
|
|
- |
Incorrect cylinder compression |
|
|
- |
Sticking or leaking valves |
|
|
- |
Excessive carbon buildup in the combustion chambers. Clean the
chambers with top engine cleaner. Follow the instructions on the
can. |
|
• |
Vacuum hoses for splits or
kinks. Verify that the routing and connections are as shown on the
vehicle emission control information label. |
|
• |
Fuel octane switch setting.
Verify the fuel octane switch is set to the proper fuel octane
rating for the fuel being used in the vehicle. |
|
• |
Turbocharger system for proper
operation, if equipped. |
|
• |
Turbocharger charge air cooler
system has no leaks, if equipped. |
|
• |
The exhaust system components
for the following: |
|
|
- |
Physical damage or possible internal failure |
|
• |
Electromagnetic interference
on the reference circuit can cause a misfire condition. You can
usually detect electromagnetic interference with a scan tool by
monitoring the engine speed parameter. A sudden increase in the
engine speed parameter with little change in actual engine speed
indicates that electromagnetic interference is present. Inspect the
high voltage components near the ignition control circuit if a
condition exists. |
|
• |
Inspect the positive crankcase
ventilation system and all connections for leaks or
restrictions. |
|
• |
Evaporative Emission (EVAP)
Canister Purge Solenoid Valve that is stuck open. |
|
• |
The engine cooling system for
the following conditions: |
|
|
- |
The engine coolant thermostat heater is working proper. Refer
to
DTC P0597-P0599 . |
2. |
If the above conditions do not
address the symptom, refer to the Additional Symptoms Tests.
|
Additional Symptoms Tests
Detonation/Spark Knock: Test the engine for an
overheating condition. Refer to
Symptoms - Engine Cooling . |
Poor Fuel Economy: Inspect for foreign
material accumulation in the throttle bore, and for carbon deposits
on the throttle plate and shaft. Also inspect for throttle body
tampering. |
Rough, Unstable, or Incorrect Idle and
Stalling: Inspect the engine mounts
Engine Mount Replacement - Right Side . |
Surges/Chuggles: Test the heated oxygen
sensors (HO2S). The HO2S should respond quickly to a change in
throttle position. If the HO2S do not respond to different throttle
positions, inspect for contamination from fuel, silicon, or the
incorrect use of room temperature vulcanizing sealant. The sensors
may have a white powdery coating and result in a high, but false,
signal voltage, which gives a rich exhaust indication. The ECM
reduces the amount of fuel delivered to the engine, causing a
driveability condition. |
Hard Start
• |
Test the engine coolant
temperature (ECT) sensor. Compare the ECT sensor value to the
intake air temperature (IAT) sensor value on a cold engine. The ECT
and IAT sensor values should be within approximately 3°C
(5°F). If the ECT sensor is out of range with the IAT sensor,
test the resistance of the ECT sensor. Refer to
Temperature Versus Resistance for resistance specifications.
Replace the ECT sensor if the resistance is not within
specification. If the sensor is within the specification, test the
ECT circuits for a high resistance. |
Hesitation, Sag, Stumble
• |
Test the manifold absolute
pressure (MAP) sensor. Refer to
DTC P0106 . |
• |
Test the generator. Refer to
Symptoms - Engine Electrical . Repair the charging system if
the generator output voltage is less than 9 V or more than 16
V. |
Poor Fuel Economy
• |
Heavy loads being carried or
towed |
• |
Acceleration rate too much or
too often |
• |
Inspect for foreign material
accumulation in the throttle bore, and for carbon deposits on the
throttle plate and shaft. Also inspect for throttle body
tampering. |
Poor Fuel Fill Quality
Difficult to fill
• |
A condition with the internal
components of the fuel tank assembly |
For more information, refer to the following:
Fuel Odor
|