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Document ID# 839324
2003 HUMMER
H2
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<H1>Hesitation, Sag, Stumble</H1>
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<TH vAlign=bottom align=middle>
Inspection/Tests</P></TH>
<TH vAlign=bottom align=middle>
Action</P></TH></TR>
<TR>
<TD vAlign=top align=left colSpan=2>
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.</P></TD></TR>
<TR>
<TD vAlign=top align=left>
Preliminary</P></TD>
<TD vAlign=top align=left>
<UL type=BULLET>
<LI>Refer to Important Preliminary Inspections Before Starting in <A
href="http://127.0.0.1:9001/servlets/CellHandler?CellId=30562&RefDoc=839324">Sympto ms
- Engine Controls</A> .
<LI>Search for bulletins.
<LI>Verify that the powertrain control module (PCM) grounds are clean,
tight, and in the proper locations. Refer to <A
href="http://127.0.0.1:9001/servlets/CellHandler?CellId=30158&RefDoc=839324">Engine
Controls Schematics</A> . </LI>[/list]</TD></TR>
<TR>
<TD vAlign=top align=left>
Sensor/System</P></TD>
<TD vAlign=top align=left>
Inspect the manifold absolute pressure (MAP) sensor
operation.</P></TD></TR>
<TR>
<TD vAlign=top align=left>
Fuel System</P></TD>
<TD vAlign=top align=left>
<UL type=BULLET>
<LI>Inspect for incorrect fuel pressure. Refer to <A
href="http://127.0.0.1:9001/servlets/CellHandler?CellId=30144&RefDoc=839324">Fuel
System Diagnosis</A> .
<LI>Inspect for a contaminated fuel condition. Refer to <A
href="http://127.0.0.1:9001/servlets/CellHandler?CellId=30353&RefDoc=839324">Alcoho l/Contaminants-in-Fuel
Diagnosis</A> .
<LI>Verify that both fuel injector fuses are not open. An open fuel
injector fuse causes 4ignition coils and 4fuel injectors not
to operate. Inspect the ignition coil circuits and the fuel injector
circuits for an intermittent short to ground. Refer to <A
href="http://127.0.0.1:9001/servlets/CellHandler?CellId=62194&RefDoc=839324">Circui t
Testing</A> and <A
href="http://127.0.0.1:9001/servlets/CellHandler?CellId=61965&RefDoc=839324">Wiring
Repairs</A> in Wiring Systems. Replace the fuse.
<LI>Inspect for the following that may cause the engine to run rich:
<UL type=SQUARE>
<LI>
<H4>
<FONT color=blue>Notice</H4></FONT>
Refer to <A
href="http://127.0.0.1:9001/servlets/CellHandler?CellId=10174&RefDoc=839324"><FONT
color=blue>Heated Oxygen and Oxygen Sensor Notice</FONT></A> in
Cautions and Notices.</P>Water intrusion in the heated oxygen sensor
(HO2S) connector
<LI>Engine oil contaminated by fuel
<LI>An evaporative emission (EVAP) canister purge condition
<LI>Incorrect fuel pressure--Refer to <A
href="http://127.0.0.1:9001/servlets/CellHandler?CellId=30144&RefDoc=839324">Fuel
System Diagnosis</A> .
<LI>Leaking fuel injectors--Refer to <A
href="http://127.0.0.1:9001/servlets/CellHandler?CellId=30144&RefDoc=839324">Fuel
System Diagnosis</A> .
<LI>An inaccurate mass air flow (MAF) sensor
<LI>Blockage on the inlet screen of the MAF sensor--Refer to <A
href="http://127.0.0.1:9001/servlets/CellHandler?CellId=30405&RefDoc=839324">Mass
Air Flow (MAF)/Intake Air Temperature (IAT) Sensor Replacement</A> .
<LI>Vacuum hoses that are split, kinked, or improperly connected
<LI>An air intake duct that is collapsed or restricted--Refer to <A
href="http://127.0.0.1:9001/servlets/CellHandler?CellId=69209&RefDoc=839324">Air
Cleaner Resonator Outlet Duct Replacement</A> .
<LI>An air filter that is dirty or restricted--Refer to <A
href="http://127.0.0.1:9001/servlets/CellHandler?CellId=30328&RefDoc=839324">Air
Cleaner Element Replacement</A> . </LI>[/list] <LI>Inspect for the following conditions that may cause the engine to
run lean:
<UL type=SQUARE>
<LI>
<H4>
<FONT color=blue>Notice</H4></FONT>
Refer to <A
href="http://127.0.0.1:9001/servlets/CellHandler?CellId=10174&RefDoc=839324"><FONT
color=blue>Heated Oxygen and Oxygen Sensor Notice</FONT></A> in
Cautions and Notices.</P>Water intrusion in the HO2S connector
<LI>An exhaust leak between the HO2S and the engine--Refer to <A
href="http://127.0.0.1:9001/servlets/CellHandler?CellId=37907&RefDoc=839324">Exhaus t
Leakage</A> in Engine Exhaust.
<LI>Vacuum leaks
<LI>Incorrect fuel pressure--Refer to <A
href="http://127.0.0.1:9001/servlets/CellHandler?CellId=30144&RefDoc=839324">Fuel
System Diagnosis</A> .
<LI>Restricted fuel injectors--Refer to <A
href="http://127.0.0.1:9001/servlets/CellHandler?CellId=30403&RefDoc=839324">Fuel
Injector Balance Test with Special Tool</A> or <A
href="http://127.0.0.1:9001/servlets/CellHandler?CellId=30404&RefDoc=839324">Fuel
Injector Balance Test with Tech 2</A> .
<LI>An inaccurate MAF sensor
<LI>Fuel contamination--Refer to <A
href="http://127.0.0.1:9001/servlets/CellHandler?CellId=30353&RefDoc=839324">Alcoho l/Contaminants-in-Fuel
Diagnosis</A> .
<LI>Vacuum hoses that are split, kinked, or improperly connected
</LI>[/list]</LI>[/list]</TD></TR>
<TR>
<TD vAlign=top align=left>
Ignition System</P></TD>
<TD vAlign=top align=left>
<UL type=BULLET>
<LI>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.
<LI>Test for proper ignition voltage output with the
J 26792
Spark Tester . Refer to <A
href="http://127.0.0.1:9001/servlets/CellHandler?CellId=30190&RefDoc=839324">Electr onic
Ignition (EI) System Diagnosis</A> for the procedure.
<LI>Remove the spark plugs and check for the following:
<UL type=SQUARE>
<LI>Correct heat range
<LI>Wet plugs
<LI>Cracks
<LI>Wear
<LI>Improper gap
<LI>Burned electrodes
<LI>Heavy deposits </LI>[/list]</LI>[/list]
Refer to <A
href="http://127.0.0.1:9001/servlets/CellHandler?CellId=30554&RefDoc=839324">Spark
Plug Inspection</A> .</P>
<UL type=BULLET>
<LI>An improper spark plug gap will cause a driveability problem. Gap
the spark plugs using a wire gage gap tool. Refer to <A
href="http://127.0.0.1:9001/servlets/CellHandler?CellId=30325&RefDoc=839324">Spark
Plug Replacement</A> .
<LI>Determine the cause of the fouling before replacing the spark plugs.
<LI>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 DTCP0300 table for diagnosis. Refer to <A
href="http://127.0.0.1:9001/servlets/CellHandler?CellId=30479&RefDoc=839324">DTC
P0300</A> .
<LI>Inspect for loose ignition coil grounds. Refer to <A
href="http://127.0.0.1:9001/servlets/CellHandler?CellId=30190&RefDoc=839324">Electr onic
Ignition (EI) System Diagnosis</A> . </LI>[/list]</TD></TR>
<TR>
<TD vAlign=top align=left>
Engine Cooling System</P></TD>
<TD vAlign=top align=left>
Inspect the engine thermostat for proper operation and for proper heat
range. Refer to <A
href="http://127.0.0.1:9001/servlets/CellHandler?CellId=37167&RefDoc=839324">Thermo stat
Diagnosis</A> in Engine Cooling.</P></TD></TR>
<TR>
<TD>
Engine Mechanical</P></TD>
<TD>
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 <A
href="http://127.0.0.1:9001/servlets/CellHandler?CellId=44076&RefDoc=839324">Cranks haft
and Bearings Cleaning and Inspection</A> in Engine Mechanical. This could
result in any of the following conditions:</P>
<UL type=BULLET>
<LI>A no start
<LI>A start and stall
<LI>Erratic performance </LI>[/list]</TD></TR>
<TR>
<TD vAlign=top align=left>
Additional Inspections</P></TD>
<TD vAlign=top align=left>
Inspect the generator output voltage. Refer to <A
href="http://127.0.0.1:9001/servlets/CellHandler?CellId=37779&RefDoc=839324">Diagno stic
System Check - Engine Electrical</A> in Engine Electrical for the
procedure. Repair the charging system if the generator output voltage is
less than 9volts or more than 16volts.</P></TD></TR></TBODY></TABLE>
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Document ID# 839324
2003 HUMMER
H2
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