NO.12 LACK/LOSS OF POWER-ACCELERATION/CRUISE [WITHOUT WU-TWC]

id0103008048c6

12

LACK/LOSS OF POWER - ACCELERATION/CRUISE

DESCRIPTION

Performance is poor under load (e.g., power decrease 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
• Improper VIS operation (if equipped)
• Improper VTCS operation
• 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
• Air cleaner restriction
• PCV valve malfunction
• Improper valve timing due to jumping out of timing belt
• 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
• Intermittent open or short of MAF sensor, TP sensor and VSS
• ATX malfunction (ATX)
• Clutch slippage (MTX)
Warning
The following troubleshooting flow chart contains the fuel system diagnosis and repair procedures. Read the following warnings before performing the fuel system services:
• 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 the "BEFORE REPAIR PROCEDURE" and "AFTER REPAIR PROCEDURE" described in this manual.
(See BEFORE REPAIR PROCEDURE.)
(See AFTER REPAIR PROCEDURE.)
Caution
• If there is foreign material on the connecting area of the quick release connector, it might damage the connector or fuel pipe. To prevent this, disconnect the connector and clean the connecting area before connecting.

Diagnostic procedure

STEP

INSPECTION

RESULTS

ACTION

1
Inspect the following:
• Vacuum connection
• Air cleaner element
• No air leakage from the intake-air system
• No restriction of the intake-air system
• Proper sealing of the intake manifold and components attached to the intake manifold; such as the IAC valve
• Fuel quality (e.g. 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 WDS or equivalent to the DLC-2.
Retrieve any continuous memory, KOEO and KOER DTCs.
If an engine stall condition exists, retrieve continuous memory and KOEO DTCs.
Are any DTCs displayed?
Yes

DTC is displayed:

Go to the appropriate DTC test.
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 WDS or equivalent to the DLC-2.
Access RPM, MAF, TP and VSS PIDs.
Monitor the PIDs while driving the vehicle.
Are the PIDs within specifications?
Yes
Go to the next step.
No

RPM PID:

Inspect the CKP sensor and related wiring harness for vibration and/or intermittent open/short circuit.

MAF PID:

Inspect for an intermittent open circuit of the MAF sensor and the related wiring harness.

TP PID:

Inspect if the TP sensor output increases smoothly.

VSS PID:

Inspect for an intermittent open circuit of the VSS and the related wiring harness.
5
Visually inspect the CKP sensor and teeth of the crankshaft pulley.
Are the CKP sensor and teeth of the crankshaft pulley normal?
Yes
Go to the next step.
No
Replace the malfunctioning parts.
6
Measure the gap between the CKP sensor and teeth of the crankshaft pulley.
Specification

0.5-1.5 mm {0.02-0.05 in}

Is the gap within specification?
Yes
Go to the next step.
No
Replace the plate.
7
Inspect the spark plugs.
Is the spark plug wet, covered with carbon, or grayish white?
Yes

Spark plug is wet or covered with carbon:

Inspect for fuel leakage from fuel injector.

Spark plug is grayish white:

Inspect for clogged fuel injector.
No
Install spark plugs on original cylinders.
Go to the next step.
8
Remove and shake the PCV valve.
Does the PCV valve rattle?
Yes
Go to the next step.
No
Replace the PCV valve.
9
Inspect for restriction in the exhaust system.
Is there any restriction?
Yes
Inspect the exhaust system.
No
Go to the next step.
10
Install a fuel pressure gauge between the fuel pipe and the fuel distributor.
Connect the WDS or equivalent to the DLC-2.
Turn ON the fuel pump using the FP PID in the output state control of the datalogger function.
Is the fuel line pressure correct?
Yes
Go to the next step.
No

Zero or low:

Inspect the fuel pump relay and fuel pump relay related circuit.
Inspect for leakage inside the pressure regulator.
Inspect for a clogged main fuel line.

High:

Inspect the pressure regulator cause for the high pressure cause.
Inspect for a clogged fuel return line.
Inspect the vacuum hose to the pressure regulator.
11
Inspect the VTCS operation.
Does the VTCS function properly?
Yes
Go to the next step.
No
Repair or replace the malfunctioning parts.
12
Note
• The following test should be performed for vehicles with VIS. Go to the next step for vehicles without VIS.
Inspect the VIS operation.
Does VIS function properly?
Yes
Go to the next step.
No
Repair or replace the malfunctioning parts.
13
Note
• The following test is for engines stalling with the A/C on. If other symptoms exist, go to the next step.
Connect pressure gauges to the A/C low and high side pressure lines.
Turn the A/C on and measure the low side and high side pressures.
Are the pressures within specification?
Yes
Go to the next step.
No
If the A/C is always on, go to symptom troubleshooting "No.24 A/C is always on or A/C compressor runs continuously".
For other symptoms, inspect following:
• Refrigerant charging amount
• Condenser fan operation
14
Inspect for A/C cut-off operation.
Does the A/C cut-off function properly?
Yes
Go to the next step.
No
Inspect the A/C cut-off system components.
15
Disconnect the vacuum hose between the purge solenoid valve and the intake manifold from the purge solenoid valve side.
Plug the open end of the vacuum hose.
Drive the vehicle.
Does the engine condition improve?
Yes
Inspect if the purge solenoid valve is stuck open mechanically.
Inspect evaporative emission control system.
No
Go to the next step.
16
Visually inspect the CMP sensor and projections of the camshaft pulley.
Are the CMP sensor and projections of the camshaft pulley normal?
Yes
Go to the next step.
No
Replace the malfunctioning parts.
17
Inspect variable valve timing control system operation.
Does the variable valve timing control system function properly?
Yes
Go to the next step.
No
Repair or replace the malfunctioning parts.
18
Is the engine compression correct?
Yes
Inspect the following:
• Valve timing.
• Internal transaxle components (ATX)
• Clutch (MTX)
• Brake system for dragging
No
Inspect for the cause.
19
Verify test results.
• If normal, return to the diagnostic index to service any additional symptoms.
• If the malfunction remains, replace or reprogram the PCM.