Suzuki XL7 2007 Service Manual page 281

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:
– The fuel system for the following:
– Correct fuel pressure—Refer to "Fuel System
Diagnosis: ".
– Fuel injectors that are leaking or improper
operation—Refer to "Fuel Injector Balance Test
with Special Tool: " or "Fuel Injector Balance
Test with Tech 2: ".
– Contaminated or a poor fuel quality condition—
Refer to "Alcohol/Contaminants-in-Fuel
Diagnosis (w/o Special Tool): " "Alcohol/
Contaminants-in-Fuel Diagnosis (w/ Special
Tool): ".
– The ignition system for the following:
– Spark plugs for incorrect heat range or an
abnormal condition—Refer to "Spark Plug
Inspection: ".
– For diagnosis of coolant or oil fouled spark
plugs—Refer to "Loss of Coolant: " or "Oil
Consumption Diagnosis: ".
– 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.
– Weak spark using the J 26792 Spark Tester—
Refer to "Electronic Ignition (EI) System
Diagnosis: ".
Engine General Information and Diagnosis:
– 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
– Items that can cause an engine to run lean or
rich—Refer to "DTC P2178, 2180, P2188, or
P2190".
– The crankshaft position (CKP) sensor for the
correct resistance—The CKP sensor resistance
may be out of range after a hot soak. The
resistance should be between 700-1200 ohms.
– The engine for the following mechanical failures—
Refer to "Symptoms - Engine Mechanical: ".
– Excessive oil in the combustion chamber or
leaking valve seals
– Incorrect cylinder compression
– Sticking or leaking valves
– Worn camshaft lobes
– Incorrect valve timing
– Broken valve springs
– Excessive carbon buildup in the combustion
chambers—Clean the chambers with top
engine cleaner. Follow the instructions on the
can.
– Incorrect engine parts
– Vacuum hoses for splits or kinks—Verify that the
routing and connections are as shown on the
Vehicle Emission Control Information label.
– Knock sensor (KS) system for excessive spark
retard activity—Refer to "Knock Sensor (KS)
System Description: " and "DTC P0326, P0327,
P0328, P0331, P0332, or P0333".
– The exhaust system components for the following:
– Physical damage or possible internal failure
– The three-way catalytic converters for a
restriction
For more information, refer to "Symptoms -
Engine Exhaust: ".
– Electromagnetic interference (EMI) on the
reference circuit can cause a misfire condition.
You can usually detect EMI 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 EMI
is present. Inspect the high voltage components
near the ignition control circuit if a condition exists.
– Inspect the positive crankcase ventilation (PCV)
system and all connections for leaks or
restrictions.
– Evaporative emission (EVAP) canister purge
solenoid that is stuck open
– The engine cooling system for the following
conditions:
1A-176