Hummer H2. Manual - part 1588

SURGES/CHUGGLES 

Electronic Ignition (EI) System Diagnosis .  

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Remove the spark plugs and inspect for the following: 

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Correct heat range  

{

Wet plugs  

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Cracks  

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Wear  

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Improper gap  

{

Burned electrodes  

{

Heavy deposits  

Refer to Spark Plug Inspection . 

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Determine the cause of the conditions before replacing the spark plugs.  

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Inspect for bare or shorted ignition wires. Refer to Spark Plug Wire 
Inspection .  

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Inspect for loose ignition coil grounds. Refer to Electronic Ignition (EI) System 
Diagnosis .  

Engine 
Mechanical

Inspect for the following conditions: 

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Excessive oil in combustion chamber or leaking valve seals - Refer to Oil 
Consumption Diagnosis in Engine Mechanical.  

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Low cylinder compression - Refer to Engine Compression Test in Engine 
Mechanical.  

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Combustion chambers for excessive carbon buildup - Clean the chambers using 
top engine cleaner. Follow the instructions on the can.  

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Incorrect basic engine parts - Inspect the following: 

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Cylinder heads - Refer to Cylinder Head Cleaning and Inspection in 
Engine Mechanical.  

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Camshaft - Refer to Camshaft and Bearings Cleaning and Inspection in 
Engine Mechanical.  

{

Pistons, etc. - Refer to Piston, Connecting Rod, and Bearings Cleaning 
and Inspection in Engine Mechanical.  

z

Inspect for excessive crankshaft endplay that will cause the crankshaft position 
(CKP) sensor reluctor wheel to move out of alignment with the CKP sensor. 
Refer to Crankshaft and Bearings Cleaning and Inspection in Engine 
Mechanical. This could result in any of the following conditions: 

{

A no start  

{

A start and stall  

{

Erratic performance  

 

2004 Hummer H2 

2004 ENGINE PERFORMANCE Engine Controls (Troubleshooting) - 4.8L, 5.3L, and 6.0L - Hummer H2

  

Surges/Chuggles 

Inspection/Tests

Action

DEFINITION: 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.
Preliminary

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Refer to Important Preliminary Inspections Before Starting in Symptoms - 
Engine Controls .  

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Search for bulletins.  

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Inspect the powertrain control module (PCM) grounds for being clean, tight, 
and in the proper locations. Refer to Power and Grounding Component 
Views in Wiring Systems and Engine Controls Schematics .  

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Verify the driver understands the operation of the transmission torque converter 
clutch (TCC) and A/C compressor operation as explained in the owners manual. 
Inform the customer how the TCC and the A/C clutch operates.  

Sensor/System

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Inspect the heated oxygen sensors (HO2S). The HO2S should respond quickly 
to different throttle positions. If they do not, inspect the HO2S for silicon or 
other contaminates from fuel or the use of improper RTV sealant. The sensors 
may have a white, powdery coating and result in a high but false signal voltage 
rich exhaust indication. The PCM will then reduce the amount of fuel delivered 
to the engine causing a severe driveability problem.  

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Inspect the mass air flow (MAF) sensor connections. Repair or replace damaged 
terminals. Refer to Connector Repairs in Wiring Systems.  

Fuel System

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Test for incorrect fuel pressure. Refer to Fuel System Diagnosis .  

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Inspect for a contaminated fuel condition. Refer to Alcohol/Contaminants-in-
Fuel Diagnosis (without Special Tool and E85) or Alcohol/Contaminants-in-
Fuel Diagnosis (with Special Tool) .  

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Verify that each injector harness is connected to the correct injector or cylinder. 
Relocate injector harnesses as necessary.  

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Inspect for the following that may cause the engine to run rich: 

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Water intrusion in the HO2S connector  

{

Engine oil contaminated by fuel  

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An evaporative emission (EVAP) canister purge condition  

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Incorrect fuel pressure - Refer to Fuel System Diagnosis .  

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Leaking fuel injectors - Refer to Fuel System Diagnosis .  

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An inaccurate MAF sensor  

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Blockage on the inlet screen of the MAF sensor - Refer to Mass Air Flow 
(MAF)/Intake Air Temperature (IAT) Sensor Replacement .  

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Vacuum hoses that are split, kinked, or improperly connected  

NOTE:

Refer to Heated Oxygen and Oxygen Sensor Notice in Cautions and 
Notices.

 

2004 Hummer H2 

2004 ENGINE PERFORMANCE Engine Controls (Troubleshooting) - 4.8L, 5.3L, and 6.0L - Hummer H2

  

{

An air intake duct that is collapsed or restricted - Refer Air Cleaner 
Resonator Outlet Duct Replacement .  

{

An air filter that is dirty or restricted-Refer to Air Cleaner Element 
Replacement .  

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Inspect for the following conditions that may cause the engine to run lean: 

{

Water intrusion in the HO2S connector  

{

An exhaust leak between the HO2S and the engine - Refer to Exhaust 
Leakage in Engine Exhaust.  

{

Vacuum leaks  

{

Incorrect fuel pressure - Refer to Fuel System Diagnosis .  

{

Restricted fuel injectors - Refer to Fuel Injector Balance Test with 
Special Tool or Fuel Injector Balance Test with Tech 2 .  

{

An inaccurate MAF sensor  

{

Fuel contamination - Refer to Alcohol/Contaminants-in-Fuel Diagnosis 
(without Special Tool and E85) or Alcohol/Contaminants-in-Fuel 
Diagnosis (with Special Tool) .  

{

Vacuum hoses that are split, kinked, or improperly connected  

NOTE:

Refer to Heated Oxygen and Oxygen Sensor Notice in Cautions and 
Notices.

Ignition System

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Soak the secondary ignition system with water from a spray bottle. Soaking the 
secondary ignition system may help locate damaged or deteriorated 
components. Look and listen for arcing or misfiring as you apply the water.  

z

Test for proper ignition voltage output with the J 26792 Spark Tester. Refer to 
Electronic Ignition (EI) System Diagnosis .  

z

Remove the spark plugs and inspect for the following: 

{

Correct heat range  

{

Wet plugs  

{

Cracks  

{

Wear  

{

Improper gap  

{

Burned electrodes  

{

Heavy deposits  

Refer to Spark Plug Inspection . 

z

An improper spark plug gap will cause a driveability problem. Gap the spark 
plugs using a wire gauge gap tool. Refer to Spark Plug Replacement .  

z

Determine the cause of the fouling before replacing the spark plugs.  

 

2004 Hummer H2 

2004 ENGINE PERFORMANCE Engine Controls (Troubleshooting) - 4.8L, 5.3L, and 6.0L - Hummer H2

  

LACK OF POWER, SLUGGISHNESS, OR SPONGINESS 

Lack of Power, Sluggishness, or Sponginess 

z

Monitor the Misfire Current Counters while driving the vehicle within the 
conditions that the misfire occurred. If a misfiring cylinder can be located, use 
the DTC P0300 table for diagnosis. Refer to DTC P0300 .  

z

Inspect for loose ignition coil grounds. Refer to Electronic Ignition (EI) 
System Diagnosis .  

Engine 
Mechanical

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Verify that the engine coolant temperature (ECT) is not above 130°C (266°F). 
This condition causes the PCM to operate in Engine Coolant Over Temperature-
Fuel Disabled Mode. While in Engine Coolant Over Temperature-Fuel Disabled 
Mode, the PCM turns fuel OFF to 4 cylinders at a time to keep engine 
temperatures from reaching damaging levels. The driver may perceive Engine 
Coolant Over Temperature-Fuel Disabled Mode as a lack of power, miss, or 
rough idle. If the vehicle operates in Engine Coolant Over Temperature-Fuel 
Disabled Mode, refer to Engine Overheating in Engine Cooling for diagnosis.  

z

Inspect for excessive crankshaft endplay that will cause the crankshaft position 
(CKP) sensor reluctor wheel to move out of alignment with the CKP sensor. 
Refer to Crankshaft and Bearings Cleaning and Inspection in Engine 
Mechanical. This could result in any of the following conditions: 

{

A no start  

{

A start and stall  

{

Erratic performance  

Additional 
Inspections

z

Visually and physically inspect vacuum hoses for splits, kinks, and proper 
connections and routing as shown on the Vehicle Emission Control Information 
label.  

z

Inspect the transmission torque converter clutch (TCC) operation. A TCC 
applying too soon can cause the engine to spark knock. Refer to Diagnostic 
Starting Point - Automatic Transmission in Automatic Transmission - 4L60-
E.  

Inspection/Tests

Action

DEFINITION: Engine delivers less than expected power. Little or no increase in speed when the 
accelerator pedal is pushed down part way.
Preliminary 
Inspections

z

Refer to Important Preliminary Inspections Before Starting in Symptoms - 
Engine Controls .  

z

Search for bulletins.  

z

Verify that the powertrain control module (PCM) grounds are clean, tight, and 
in the proper locations. Refer to Power and Grounding Component Views in 
Wiring Systems and Engine Controls Schematics .  

z

Remove the air filter element and inspect for dirt or for restrictions. Refer to Air 
Cleaner Element Replacement and replace as necessary.  

 

2004 Hummer H2 

2004 ENGINE PERFORMANCE Engine Controls (Troubleshooting) - 4.8L, 5.3L, and 6.0L - Hummer H2