Hummer H2. Manual — part 1590

HESITATION, SAG, STUMBLE

Hesitation, Sag, Stumble

Inspection in Engine Mechanical.

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

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

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Refer to Symptoms - Engine Mechanical in Engine Mechanical.

Additional
Inspections

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Inspect the park/neutral position (PNP) switch operation. Refer to Diagnostic
System Check - Automatic Transmission in Automatic Transmission -
4L60-E.

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

Inspection/Tests

Action

DEFINITION: Momentary lack of response as the accelerator is pushed down. Can occur at any vehicle
speed. Usually more pronounced when first trying to make the vehicle move, as from a stop. May cause
the engine to stall if severe enough.
Preliminary

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

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Search for bulletins.

z

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

Sensor/System

Inspect the manifold absolute pressure (MAP) sensor operation.

Fuel System

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Inspect 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 both fuel injector fuses are not open. An open fuel injector fuse
causes 4 ignition coils and 4 fuel injectors not to operate. Inspect the ignition
coil circuits and the fuel injector circuits for an intermittent short to ground.
Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Replace the
fuse.

z

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

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

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Water intrusion in the heated oxygen sensor (HO2S) connector

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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 mass air flow (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

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

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

z

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

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Water intrusion in the HO2S connector

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

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Vacuum leaks

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Incorrect fuel pressure - Refer to Fuel System Diagnosis .

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

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An inaccurate MAF sensor

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Fuel contamination - 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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Vacuum hoses that are split, kinked, or improperly connected

NOTE:

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

Ignition System

z

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 water.

z

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

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Remove the spark plugs and check for the following:

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Correct heat range

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Wet plugs

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Cracks

2004 Hummer H2

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

CUTS OUT, MISSES

Cuts Out, Misses

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Wear

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Improper gap

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Burned electrodes

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Heavy deposits

Refer to Spark Plug Inspection .

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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 .

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

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Monitor the Misfire Current Counters while driving the vehicle in 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 Cooling
System

Inspect the engine thermostat for proper operation and for proper heat range. Refer to
Thermostat Diagnosis in Engine Cooling.

Engine
Mechanical

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:

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A no start

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A start and stall

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Erratic performance

Additional
Inspections

Inspect the generator output voltage. Refer to Diagnostic System Check - Engine
Electrical in Engine Electrical for the procedure. Repair the charging system if the
generator output voltage is less than 9 volts or more than 16 volts.

Inspections

Action

DEFINITION: Steady pulsation or jerking that follows engine speed, usually more pronounced as 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 low speed.
Preliminary

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 .

2004 Hummer H2

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

z

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

Fuel System

z

Inspect the fuel injectors. Refer to Fuel Injector Coil Test .

z

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

z

Inspect for a restricted fuel filter. Refer to Fuel System Diagnosis .

z

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) .

z

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

{

Water intrusion in the heated oxygen sensor (HO2S) connector

{

Engine oil contaminated by fuel

{

An evaporative emission (EVAP) canister purge condition

{

Incorrect fuel pressure - Refer to Fuel System Diagnosis .

{

A leaking fuel pressure regulator - Refer to Fuel System Diagnosis .

{

Leaking fuel injectors - Refer to Fuel System Diagnosis .

{

An inaccurate mass air flow (MAF) sensor

{

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

{

Vacuum hoses that are split, kinked, or improperly connected

{

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

{

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

z

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 .

NOTE:

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

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