NO.12 LACK/LOSS OF POWER-ACCELERATION/CRUISE [L8, LF]

id0103a0804800

12 | LACK/LOSS OF POWER—ACCELERATION/CRUISE
--- | ---
DESCRIPTION | • Performance is poor under load (such as power down when climbing hills).
POSSIBLE CAUSE | • Drive-by-wire control system operates with brake override system (from NC18**-215550,NC18**-250831,NC30**-202488,NCA8**-251024) • Poor fuel quality • Air leakage from intake-air system • Restriction in intake-air system • Throttle valve malfunction • Vacuum leakage • Engine overheating • Intermittent open or short circuit of the following: ― APP sensor ― TP sensor ― MAF sensor ― VSS ― CKP sensor ― IAT sensor • Erratic signal from CKP sensor • Spark plug malfunction • Improper operation of electronic throttle control system • Restriction in exhaust system • Fuel supply system malfunction ― Fuel pump and fuel pump relay related circuit malfunction ― Fuel line clogging ― Fuel pump unit malfunction ― Fuel injector malfunction • Improper operation of variable tumble control • Improper operation of variable intake air control • Improper operation of A/C system • Improper operation of A/C cut-off control system • Purge solenoid valve malfunction • EVAP control system malfunction • Erratic signal from CMP sensor • Improper operation of EGR control system • Improper operation of variable valve timing control system • Low engine compression • PCV valve malfunction • Brake system malfunction • Clutch (MT) malfunction • Internal AT components (AT) malfunction • Valve timing malfunction • PCM malfunction 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 “BEFORE SERVICE PRECAUTION” and “AFTER SERVICE PRECAUTION” described in this manual. (See BEFORE SERVICE PRECAUTION [L8, LF].) (See AFTER SERVICE PRECAUTION [L8, LF].) Caution • Disconnecting/connecting quick release connector without cleaning it may possibly 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*1 | CONFIRM DRIVE-BY-WIRE CONTROL SYSTEM OPERATES WITH BRAKE OVERRIDE SYSTEM • Retrieve the PCM DTC using the M-MDS. (See ON-BOARD DIAGNOSTIC TEST [L8, LF].) • Is the DTC P2299 present? | Yes | Go to the applicable DTC inspection. (drive-by-wire control system operates with brake override system.) (See DTC P2299 [L8, LF].)
No | Go to the next step.
2 | Verify the following: • Fuel quality (such as proper octane, contamination, winter/summer blend) • No air leakage from intake-air system • No restriction of intake-air system • Proper sealing of intake manifold and components attached to intake manifold; such as EGR valve • Restriction in the intake-air system (such as air cleaner element, fresh air duct) • Vacuum connection Is there any malfunction? | Yes | Repair or replace the malfunctioning part according to the inspection results. Repeat Step 2.
No | Go to the next step.
3 | Connect the M-MDS to the DLC-2. Perform the KOEO/KOER self test and the DTC Reading Procedure. If engine stall condition exists, perform the KOEO self test and the DTC Reading Procedure. (See KOEO/KOER SELF TEST [L8, LF].) (See ON-BOARD DIAGNOSTIC TEST [L8, LF].) Are any DTCs present? | Yes | Go to the appropriate DTC inspection. (See DTC TABLE [L8, LF].)
No | Go to the next step.
4 | Is the engine overheating? | Yes | Go to the symptom troubleshooting “NO.17 COOLING SYSTEM CONCERNS-OVERHEATING”. (See NO.17 COOLING SYSTEM CONCERNS-OVERHEATING [L8, LF].)
No | Go to the next step.
5 | Connect the M-MDS to the DLC-2. Perform the PID/DATA Monitor and Record Procedure and access the following PIDs: (See ON-BOARD DIAGNOSTIC TEST [L8, LF].) • APP1 • APP2 • TP • MAF • VSS • RPM • IAT Access the PIDs while driving the vehicle. Are the PIDs normal? (See PCM INSPECTION [L8, LF].) | Yes | Go to the next step.
No | APP1, APP2: • Inspect if the APP sensor output increase smoothly. (See ACCELERATOR PEDAL POSITION (APP) SENSOR INSPECTION [L8, LF].) TP: • Inspect if the TP sensor output increases smoothly. (See THROTTLE POSITION (TP) SENSOR INSPECTION [L8, LF].) MAF: • Inspect the MAF sensor and related wiring harness for intermittent open circuit. (See MASS AIR FLOW (MAF) SENSOR INSPECTION [L8, LF].) VSS: • Inspect the VSS and related wiring harness for intermittent open circuit. (See VEHICLE SPEED SENSOR (VSS) INSPECTION [SJ6A-EL].) RPM: • Inspect the CKP sensor and related wiring harness for vibration and/or intermittent open/short circuit. (See CRANKSHAFT POSITION (CKP) SENSOR INSPECTION [L8, LF].) IAT: • Inspect for air suction in intake-air system. • If normal, inspect the IAT senor and related wiring harness for intermittent short circuit. (See INTAKE AIR TEMPERATURE (IAT) SENSOR INSPECTION [L8, LF].) Repair or replace the malfunctioning part according to the inspection results.
6 | Visually inspect the CKP sensor and teeth of crankshaft pulley. Is there any malfunction? | Yes | Repair or replace the malfunctioning part according to the inspection results.
No | Go to the next step.
7 | Inspect spark plug condition. (See SPARK PLUG INSPECTION [L8, LF].) 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 injector. Spark plug is grayish white: • Inspect for clogged fuel injector. Repair or replace the malfunctioning part according to the inspection results.
No | Install spark plugs on original cylinders. Go to the next step.
8 | Perform the Electronic Throttle Control System Inspection. (See ENGINE CONTROL SYSTEM OPERATION INSPECTION [L8, LF].) Does the electronic throttle control system operate properly? | Yes | Go to the next step.
No | Repair or replace the malfunctioning part according to the inspection results.
9 | Visually inspect the exhaust system part. Is there any deformed exhaust system part? | Yes | Repair or replace the malfunctioning part according to the inspection results.
No | Go to the next step.
10 | Install the fuel pressure gauge between the fuel pipe and fuel distributor. Connect the M-MDS to the DLC-2. Perform the PID/DATA Monitor and Record Procedure. (See ON-BOARD DIAGNOSTIC TEST [L8, LF].) Turn the fuel pump on using FP PID in output state control of datalogger function. Is fuel line pressure correct? (See FUEL LINE PRESSURE INSPECTION [L8, LF].) | Yes | Go to the next step.
No | Zero or low: • Inspect the fuel pump and fuel pump relay related circuit. • Inspect for clogged fuel line. • If there is no malfunction: ― Replace the fuel pump unit. (See FUEL PUMP UNIT REMOVAL/INSTALLATION [L8, LF].) • If there is a malfunction: ― Repair or replace the malfunctioning part according to the inspection results. High: • Replace the fuel pump unit. (See FUEL PUMP UNIT REMOVAL/INSTALLATION [L8, LF].)
11 | Perform the Variable Tumble Control Operation Inspection. (See ENGINE CONTROL SYSTEM OPERATION INSPECTION [L8, LF].) Does the variable tumble control normal? | Yes | Go to the next step.
No | Repair or replace the malfunctioning part according to the inspection results.
12 | Perform the Variable Intake Air Control Operation Inspection. (See ENGINE CONTROL SYSTEM OPERATION INSPECTION [L8, LF].) Does the variable intake air function properly? | Yes | Go to the next step.
No | Repair or replace the malfunctioning part according to the inspection results.
13 | Note • Following test is for lack/loss of power with the A/C on. If other symptom exists, go to the next step. Connect the pressure gauge to the A/C low and high pressure side lines. Turn the A/C on and measure low side and high side pressure. Are pressure within specifications? (See REFRIGERANT PRESSURE CHECK.) | Yes | Go to the next step.
No | If A/C is always on: • Go to the 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 [L8, LF].) For other symptoms: • Inspect the following: ― Refrigerant charging amount ― Condenser fan operation • Repair or replace the malfunctioning part according to the inspection results.
14 | Perform the A/C Cut-off Control System Inspection. (See ENGINE CONTROL SYSTEM OPERATION INSPECTION [L8, LF].) Does A/C cut-off work properly? | Yes | Go to the next step.
No | Inspect the A/C cut-off system components. Repair or replace the malfunctioning part according to the inspection results.
15 | Disconnect the vacuum hose between the purge solenoid valve and the intake manifold from the purge solenoid valve side. Plug the opening end of vacuum hose. Drive the vehicle. Does the engine condition improve? | Yes | Inspect if the purge solenoid valve is stuck open. (See PURGE SOLENOID VALVE INSPECTION [L8, LF].) Inspect the EVAP control system. Repair or replace the malfunctioning part according to the inspection results.
No | Go to the next step.
16 | Visually inspect the CMP sensor and projections of the camshaft pulley. Is there any malfunction? | Yes | Repair or replace the malfunctioning part according to the inspection results.
No | Go to the next step.
17 | Perform the EGR Control System Inspection. (See ENGINE CONTROL SYSTEM OPERATION INSPECTION [L8, LF].) Is EGR control system normal? | Yes | Go to the next step.
No | Repair or replace the malfunctioning part according to the inspection results.
18 | Perform the Variable Valve Timing Control System Operation Inspection. (See ENGINE CONTROL SYSTEM OPERATION INSPECTION [L8, LF].) Does the variable valve timing control system operate properly? | Yes | Go to the next step.
No | Repair or replace the malfunctioning part according to the inspection results.
19 | Perform the “COMPRESSION INSPECTION”. (See COMPRESSION INSPECTION [L8, LF].) Is the engine compression correct? | Yes | Go to the next step.
No | Inspect for cause.
20 | Inspect the PCV valve. (See POSITIVE CRANKCASE VENTILATION (PCV) VALVE INSPECTION [L8, LF].) Is there any malfunction? | Yes | Replace the PCV valve.
No | Inspect the following: • Brake system for dragging • Clutch (MT) • Internal AT components (AT) • Valve timing Repair or replace the malfunctioning part according to the inspection results.
21 | Verify test results. • If normal, return to diagnostic index to service any additional symptoms. (See ENGINE SYMPTOM TROUBLESHOOTING [L8, LF].) • If malfunction remains, inspect related Service information perform repair or diagnosis. ― If vehicle repaired, troubleshooting completed. ― If vehicle not repaired or additional diagnostic information not available, replace the PCM. (See PCM REMOVAL/INSTALLATION [L8, LF].)

*1 :From NC18**-215550,NC18**-250831,NC30**-202488,NCA8**-251024