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NO.10 LOW IDLE/STALLS DURING DECELERATION

BHE010300103W12

10 | LOW IDLE/STALLS DURING DECELERATION
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DESCRIPTION | • The engine stops unexpectedly at the beginning of deceleration or recovery from deceleration.
POSSIBLE CAUSE | • Vacuum leakage • Air leakage from intake-air system • Air suction at intake-air system (between MAF sensor and intake port) • Improper operation of drive-by-wire control system (abnormal accelerator position ad TP signals to PCM) • Drive-by-wire control system operates in fail-safe function (abnormal accelerator position and TP signals to PCM) • Throttle body malfunction (restriction, stuck closed) • Evaporative emission control system malfunction • Improper operation of fuel cut control • Fuel injector improper operation • Fuel injector malfunction (leakage, clogging, improper injection amount) • Inadequate fuel pressure • Pressure regulator malfunction (integrated in fuel pump unit) • Fuel pump mechanical malfunction • Fuel line restriction or clogging • MAF sensor improper installation • MAF sensor or related circuit malfunction (abnormal signal to PCM) • Brake switch or related circuit malfunction (abnormal signal to PCM) • Neutral/CPP switch or related circuit malfunction (abnormal signal to PCM) • TR switch or related circuit malfunction (abnormal signal to PCM) • Low engine compression – Engine internal malfunction – Abnormal engine oil condition (viscosity, deterioration) – Low oil pressure – Excessive fuel pressure – Air mixed in oil line – Metering oil pump malfunction • Leakage or clogging in oil pipe • Leakage or clogging in oil nozzle • Improper A/C magnetic clutch malfunction • Misfire • Improper operation of torque converter clutch control (AT) • Loose installation of engine mounts Warning The following troubleshooting flow chart contains 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 REPAIR PROCEDURE" and "AFTER REPAIR PROCEDURE" described in this manual. (See BEFORE REPAIR PROCEDURE.) (See AFTER REPAIR PROCEDURE.) 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
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1 | Does the engine idle roughly? | Yes | Go to the symptom troubleshooting "No.8 Engine runs rough/rolling idle". (See NO.8 ENGINE RUNS ROUGH/ROLLING IDLE.)
No | Go to the next step.
2 | Turn off the A/C switch and the fan switch. Does the A/C magnetic clutch engage? | Yes | 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.)
No | Go to the next step.
3 | Does the engine knock/ping/detonate? | Yes | Go to the symptom troubleshooting "No.13 Knocking/pinging/detonation-Acceleration/cruise". (See NO.13 KNOCKING/PINGING/DETONATION-ACCELERATION/CRUISE.)
No | Go to the next step.
4 | Verify the following: • Proper routing of and no damage to vacuum lines • No air leakage from intake-air system • Engine mount installation condition (loose) Are all the items normal? | Yes | Go to the next step.
No | Service if necessary. Repeat Step 4.
5 | Connect the WDS or equivalent to the DLC-2. Retrieve any continuous memory, KOEO and KOER DTCs. Are there any DTCs displayed? | Yes | DTC is displayed: Go to the applicable DTC inspection. (See DTC TABLE.)
No | No DTC is displayed: Go to the next step.
6 | Perform the drive-by-wire control system operation inspection. (See Drive-by-wire Control System Inspection.) Does the drive-by-wire control system work properly? | Yes | Go to the next step.
No | Repair or replace the malfunctioning part according to the drive-by-wire control system operation inspection results.
7 | Disconnect the vacuum hose between the purge solenoid valve and the intake manifold at the quick release connector. Plug the opening end of the vacuum hose. Drive the vehicle. Does the engine condition improve? | Yes | Inspect the evaporative emission control system.
No | Go to the next step.
8 | Perform the fuel injector operation inspection. (See Fuel Injector Operation Inspection.) Does the fuel injector operate properly? | Yes | Go to the next step.
No | Repair or replace the malfunctioning parts, according to the fuel injector inspection results.
9 | Connect the WDS or equivalent to the DLC-2. Access APP, TP_REL, MAF, VSS, BOO, CPP (MT), CPP/PNP (MT) and TR PIDs. Monitor each PID while driving the vehicle. (See PCM INSPECTION.) Are the PIDs normal? | Yes | Go to the next step.
No | APP PID: Inspect the APP sensor. (See ACCELERATOR PEDAL POSITION (APP) SENSOR INSPECTION.) TP_REL PID: Inspect the TP sensor. (See THROTTLE POSITION (TP) SENSOR INSPECTION.) MAF PID: Inspect the MAF sensor. (See MASS AIR FLOW (MAF) SENSOR INSPECTION.) VSS PID: Inspect DSC system. (See DTC Table.) BOO PID: Inspect the brake switch. (See BRAKE SWITCH INSPECTION.) CPP PID: Inspect the CPP switch (MT). (See CLUTCH PEDAL POSITION (CPP) SWITCH INSPECTION.) CPP/PNP PID: Inspect the neutral switch (MT). (See NEUTRAL SWITCH INSPECTION.) TR PID: Inspect the TR switch and the communication line (PCM-TCM) (AT). (See TRANSMISSION RANGE (TR) SWITCH INSPECTION.)
10 | Turn the ignition switch off. Disconnect the fuel line quick release connector and install the fuel gauge to the fuel line. Inspect fuel line pressure while engine running. (See FUEL LINE PRESSURE INSPECTION.) Is the fuel line pressure normal? | Yes | Go to the next step.
No | Zero or low: Inspect for clogged fuel line. If normal, replace the fuel pump unit. (See FUEL PUMP UNIT REMOVAL/INSTALLATION.) High: Replace the fuel pump unit. (See FUEL PUMP UNIT REMOVAL/INSTALLATION.)
11 | Perform the fuel injector operation inspection. (See Fuel Injector Operation Inspection.) Are the fuel injectors operating properly? | Yes | Go to the next step.
No | Repair or replace the malfunctioning parts, according to the fuel injector operation inspection results.
12 | Inspect the fuel injectors for the following: (See FUEL INJECTOR INSPECTION.) • Leakage • Clogging • Injector amount Are the injectors normal? | Yes | Go to the next step.
No | Replace the suspected fuel injector.
13 | Inspect the engine compression. (See COMPRESSION INSPECTION.) Is it normal? | Yes | Go to Step 19.
No | Go to the next step.
14 | Perform the metering oil pump control inspection. (See Metering Oil Pump Control Inspection.) Does the metering oil pump control operate properly? | Yes | Go to the next step.
No | Repair or replace the malfunctioning part according to the inspection results. After that overhaul or replace the engine. (See Engine Workshop Manual.)
15 | Check the engine oil condition. Is the engine oil low viscosity and/or is there a gasoline odor? | Yes | Replace engine oil. Inspect the ECT sensor and the related wiring harnesses. (See ENGINE COOLANT TEMPERATURE (ECT) SENSOR INSPECTION.) After that overhaul or replace the engine. (See Engine Workshop Manual.)
No | Go to the next step.
16 | Inspect the oil pressure. (See OIL PRESSURE INSPECTION.) Is the oil pressure within the specification? | Yes | Go to the next step.
No | Repair or replace the malfunctioning part according to the inspection results. After that overhaul or replace the engine. (See Engine Workshop Manual.)
17 | Turn the ignition switch off. Disconnect fuel line quick release connector and install the fuel gauge to the fuel line. Start the engine and run it at idle. Measure the fuel line pressure at idle. Is the fuel line pressure correct at idle? (See FUEL LINE PRESSURE INSPECTION.) | Yes | Go to the next step.
No | Replace the fuel pump unit. (See FUEL PUMP UNIT REMOVAL/INSTALLATION.) After that overhaul or replace the engine. (See Engine Workshop Manual.)
18 | Check the oil pipe between the metering oil pump and the metering oil nozzle. Is there any air and/or clogging in the oil pipe? | Yes | Inspect and repair for leakage and/or clogging in the oil passage at engine. After that overhaul or replace the engine. (See Engine Workshop Manual.)
No | Overhaul or replace the engine. (See Engine Workshop Manual.)
19 | Note • The following test is for AT models. Go to "Yes" action for MT models. Inspect the torque converter clutch control. (See ROAD TEST.) Does the torque converter clutch control operate properly? | Yes | Inspect for the following: • Blockage at intake-air system (between MAF sensor and intake ports) • Maf sensor installation
No | Repair or replace the malfunctioning parts, according to the torque converter clutch control inspection results.
20 | Verify test results. • If normal, return to the diagnostic index to service any additional symptoms. • If the malfunction remains, inspect the related Service Information and perform the repair or diagnosis.