NO.12 LACK/LOSS OF POWER-ACCELERATION/CRUISE [MZI-3.7]

id0103d2804800

12

LACK/LOSS OF POWER—ACCELERATION/CRUISE
DESCRIPTION
Performance is poor under load (such as power down when climbing hills).
POSSIBLE CAUSE
•  Improper A/C system operation
•  Erratic signal or no signal from CMP sensor
•  Air leakage from intake-air system parts
•  Restriction in intake-air system
•  Intake air temperature too hot
•  Improper operation of electronic throttle control system
•  Purge control solenoid malfunction
•  Brake dragging
•  Erratic signal from CKP sensor
•  Low engine compression
•  Vacuum leakage
•  Poor fuel quality
•  Erratic signal to ignition coil
•  Engine overheating
•  Throttle body malfunction
•  Spark plug malfunction
•  PCV valve malfunction
•  Improper valve timing due to jumping out of timing chain
•  Improper variable valve timing control operation
•  Restriction in exhaust system
•  Intermittent open or short in fuel pump related circuit
•  Inadequate fuel pressure
•  Fuel pump mechanical malfunction
•  Fuel line restriction or clogging
•  Fuel leakage from fuel injector
•  Fuel injector clogging
•  Erratic signal from accelerator pedal position sensor
•  Erratic signal from TP sensor
•  Intermittent open or short circuit in MAF sensor, Accelerator pedal position sensor, TP sensor, IAT sensor and VSS
•  ATX malfunction
Warning
The following troubleshooting flow chart contains the fuel system diagnosis and repair procedures. Read the following warnings before servicing the fuel system:
•  Fuel vapor is hazardous. It can easily ignite, causing serious injury and damage. Always keep sparks and flames away from fuel.
•  Fuel line spills and leakage are dangerous. Fuel can ignite and cause serious injuries or death and damage. Fuel can also irritate skin and eyes. To prevent this, always complete “BEFORE SERVICE PRECAUTION” and “AFTER SERVICE PRECAUTION” described in this manual.
Caution
•  Disconnecting/connecting quick release connector without cleaning it may cause damage to fuel pipe and quick release connector. Always clean quick release connector joint area before disconnecting/connecting, and make sure that it is free of foreign material.

Diagnostic procedure

STEP

INSPECTION

RESULTS

ACTION
1
Verify the following:
•  Vacuum connection
•  Restriction in intake-air system (such as air cleaner element, fresh air duct)
•  No air leakage from intake-air system
•  No restriction of intake-air system
•  Proper sealing of intake manifold and components attached to intake manifold
•  Fuel quality (such as proper octane, contamination, winter/summer blend)
Are all items normal?
Yes
Go to the next step.
No
Service if necessary.
Repeat Step 1.
2
Connect the M-MDS to the DLC-2.
Turn the ignition switch to the ON position (Engine off).
Retrieve any DTCs.
Are there any DTCs displayed?
Yes
DTC is displayed:
Go to the appropriate DTC inspection.
No
No DTC is displayed:
Go to the next step.
3
Is the engine overheating?
Yes
Go to symptom troubleshooting “No.17 Cooling system concerns-Overheating”.
No
Go to the next step.
4
Connect the M-MDS to the DLC-2.
Access APP1, APP2, APP3, RPM, MAF, TP1, TP2, IAT and VSS PIDs.
Drive vehicle while monitoring PIDs.
Are PIDs within specifications?
(See PCM INSPECTION [MZI-3.7].)
Yes
Go to the next step.
No
APP1, APP2, APP3 PIDs:
Inspect if output signal accelerator pedal position sensor changes smoothly.
RPM PID:
Inspect CKP sensor and related wiring harness for vibration or intermittent open/short circuit or both.
MAF PID:
Inspect for intermittent open circuit of MAF sensor and related wiring harness.
TP1, TP2 PID:
Inspect if output signal TP sensor changes smoothly.
IAT PID:
Inspect for air suction in intake-air system.
If normal, inspect intermittent short circuit of IAT sensor and related wiring harnesses.
VSS PID:
Inspect for intermittent open circuit of VSS and related wiring harness.
5
Visually inspect the CKP sensor and teeth of crankshaft pulley.
Are the CKP sensor and teeth of crankshaft pulley normal?
Yes
Go to the next step.
No
Replace the malfunctioning part.
6
Inspect the spark plug condition.
Is spark plug wet, covered with carbon or grayish white?
Yes
Spark plug is wet or covered with carbon:
Inspect the fuel injector for fuel leakage.
Inspect spark plug and high-tension lead.
Spark plug is grayish white:
Inspect the fuel injector for clogging.
No
Install the spark plugs on original cylinders.
Go to the next step.
7
Remove and shake the PCV valve.
Does the PCV valve rattle?
Yes
Go to the next step.
No
Replace PCV valve.
8
Perform electronic throttle control system operation inspection.
(See ENGINE CONTROL SYSTEM OPERATION INSPECTION [MZI-3.7].)
Does electronic throttle control system function properly?
Yes
Go to the next step.
No
Repair or replace the malfunctioning part according to electronic throttle control system operation inspection results.
9
visually inspect deformed exhaust system part.
Is there any deformed exhaust system part?
Yes
Replace the suspected part.
No
Go to the next step.
10
Inspect the fuel line pressure.
(See FUEL LINE PRESSURE INSPECTION [MZI-3.7].)
Is the fuel line pressure correct?
Yes
Go to the next step.
No
Repair or replace the malfunctioning part.
11
Note
•  The following test is for engine stalling with the A/C on concern. If other symptoms exist, go to the next step.
Connect pressure gauge to the A/C low and high side pressure lines.
Turn the A/C on and measure low side and high side pressures.
Are pressures within specifications?
(See REFRIGERANT PRESSURE CHECK.)
Yes
Go to the next step.
No
If A/C is always on, go to symptom troubleshooting “No.24 A/C is always on or A/C compressor runs continuously”.
(See NO.24 A/C IS ALWAYS ON OR A/C COMPRESSOR RUNS CONTINUOUSLY [MZI-3.7].)
For other symptoms, inspect the following:
•  Refrigerant charging amount
•  Condenser fan operation
12
Inspect for A/C cut‐off operation.
(See ENGINE CONTROL SYSTEM OPERATION INSPECTION [MZI-3.7].)
Does the A/C cut-off function properly?
Yes
Go to the next step.
No
Inspect A/C cut‐off system components.
13
Disconnect the vacuum hose between the purge solenoid valve and the intake manifold from purge solenoid valve side.
Plug opening end of vacuum hose.
Drive the vehicle.
Does the engine condition improve?
Yes
Inspect if purge solenoid valve is stuck open mechanically.
Inspect the evaporative emission control system.
(See ENGINE CONTROL SYSTEM OPERATION INSPECTION [MZI-3.7].)
No
Go to the next step.
14
Visually inspect the CMP sensor and projections of camshaft pulley.
Are the CMP sensor and projections of camshaft pulley normal?
Yes
Go to the next step.
No
Replace the malfunctioning part.
15
Inspect the variable valve timing control system operation.
(See ENGINE CONTROL SYSTEM OPERATION INSPECTION [MZI-3.7].)
Does the variable valve timing control system function properly?
Yes
Go to the next step.
No
Repair or replace the malfunctioning part according to variable valve timing control system inspection results.
16
Is the engine compression correct?
Yes
Inspect the following:
•  Valve timing
•  Internal transaxle components
•  Brake system for dragging
No
Inspect for cause.
17
•  Verify test results.
―  If normal, return to diagnostic index to service any additional symptoms.
―  If malfunction remains, inspect related Service Information and perform repair or diagnosis.
•  If vehicle is repaired, troubleshooting completed.
•  If vehicle is not repaired or additional diagnostic information is not available, replace the PCM.