NO.11 ENGINE STALLS/QUITS, ENGINE RUNS ROUGH, MISSES, BUCK/JERK, HESITATION/STUMBLE, SURGES [L8, LF, L5]

11	ENGINE STALLS/QUITS — ACCELERATION/CRUISE ENGINE RUNS ROUGH — ACCELERATION/CRUISE MISSES — ACCELERATION/CRUISE BUCK/JERK — ACCELERATION/CRUISE/DECELERATION HESITATION/STUMBLE — ACCELERATION SURGES — ACCELERATION/CRUISE
DESCRIPTION	• Engine stops unexpectedly at the beginning of acceleration or during acceleration. • Engine stops unexpectedly while cruising. • Engine speed fluctuates during acceleration or cruising. • Engine misses during acceleration or cruising. • Vehicle bucks/jerks during acceleration, cruising, or deceleration. • Momentary pause at beginning of acceleration or during acceleration • Momentary minor irregularity in engine output
POSSIBLE CAUSE	• Improper A/C system operation • Erratic signal or no signal from CMP sensor • Air leakage from intake air system parts • Purge solenoid valve malfunction • Improper operation of electronic throttle control system • EGR valve malfunction • Erratic signal from CKP sensor • Low engine compression • Vacuum leakage • Poor fuel quality • Main relay intermittent malfunction • Throttle body malfunction • Engine overheating • Spark plug malfunction • Improper air/fuel mixture ratio control operation • Improper variable tumble control operation • Erratic signal to ignition coil • Air cleaner restriction • PCV valve malfunction • Fuel flow into evaporative purge hose • Improper valve timing due to jumping out timing chain • Restriction in exhaust system • Intermittent open or short circuit in fuel pump circuit • Inadequate fuel pressure • Fuel pump mechanical malfunction • Check valve (two-way) malfunction integrated with fuel tank • Fuel leakage from fuel injector • Fuel injector clogging • Fuel line restriction or clogging • Pressure regulator malfunction (built-in fuel pump unit) • Erratic signal form APP sensor • Erratic signal form TP sensor • Intermittent open or short circuit of MAF sensor, TP sensor, APP sensor and VSS • ATX malfunction (ATX) • Clutch slippage (MTX) • Improper variable intake air control operation (LF, L5) • Loose attaching bolts or worn engine mounts 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. (See BEFORE SERVICE PRECAUTION [L8, LF, L5].) (See AFTER SERVICE PRECAUTION [L8, LF, L5].) Caution • Disconnecting/connecting the quick release connector without cleaning it may cause damage to the fuel pipe and the quick release connector. Always clean the quick release connector joint area before disconnecting/connecting, and make sure that it is free of foreign material.

ENGINE STALLS/QUITS — ACCELERATION/CRUISE

ENGINE RUNS ROUGH — ACCELERATION/CRUISE

MISSES — ACCELERATION/CRUISE

BUCK/JERK — ACCELERATION/CRUISE/DECELERATION

HESITATION/STUMBLE — ACCELERATION

SURGES — ACCELERATION/CRUISE

DESCRIPTION

• Engine stops unexpectedly at the beginning of acceleration or during acceleration.

• Engine stops unexpectedly while cruising.

• Engine speed fluctuates during acceleration or cruising.

• Engine misses during acceleration or cruising.

• Vehicle bucks/jerks during acceleration, cruising, or deceleration.

• Momentary pause at beginning of acceleration or during acceleration

• Momentary minor irregularity in engine output

POSSIBLE CAUSE

• Improper A/C system operation

• Erratic signal or no signal from CMP sensor

• Air leakage from intake air system parts

• Purge solenoid valve malfunction

• Improper operation of electronic throttle control system

• EGR valve malfunction

• Erratic signal from CKP sensor

• Low engine compression

• Vacuum leakage

• Poor fuel quality

• Main relay intermittent malfunction

• Throttle body malfunction

• Engine overheating

• Spark plug malfunction

• Improper air/fuel mixture ratio control operation

• Improper variable tumble control operation

• Erratic signal to ignition coil

• Air cleaner restriction

• PCV valve malfunction

• Fuel flow into evaporative purge hose

• Improper valve timing due to jumping out timing chain

• Restriction in exhaust system

• Intermittent open or short circuit in fuel pump circuit

• Inadequate fuel pressure

• Fuel pump mechanical malfunction

• Check valve (two-way) malfunction integrated with fuel tank

• Fuel leakage from fuel injector

• Fuel injector clogging

• Fuel line restriction or clogging

• Pressure regulator malfunction (built-in fuel pump unit)

• Erratic signal form APP sensor

• Erratic signal form TP sensor

• Intermittent open or short circuit of MAF sensor, TP sensor, APP sensor and VSS

• ATX malfunction (ATX)

• Clutch slippage (MTX)

• Improper variable intake air control operation (LF, L5)

• Loose attaching bolts or worn engine mounts

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.

(See BEFORE SERVICE PRECAUTION [L8, LF, L5].)

(See AFTER SERVICE PRECAUTION [L8, LF, L5].)

Caution

• Disconnecting/connecting the quick release connector without cleaning it may cause damage to the fuel pipe and the quick release connector. Always clean the quick release connector joint area before disconnecting/connecting, and make sure that it is free of foreign material.

STEP	INSPECTION	RESULTS	ACTION
1	Verify the following: • Vacuum connection • Air cleaner element • No air leakage from intake air system • No restriction of the intake air system • Proper sealing of intake manifold and components attached to intake manifold: such as EGR valve • Ignition wiring • Fuel quality (such as proper octane, contamination, winter/summer blend) • Electrical connections • Smooth operation of the throttle valve Are all the items normal?	Yes	Go to the next step.
No	Service if necessary. Repeat Step 1.
2	Connect the M-MDS to the DLC-2. Switch the ignition to ON (Engine off). Retrieve any DTCs. Are there any DTCs displayed?	Yes	DTC is displayed: Go to the appropriate DTC inspection. (See DTC TABLE [L8, LF, L5].)
No	No DTC is displayed: Go to the next step.
3	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, L5].)
No	Go to the next step.
4	Connect the M-MDS to the DLC-2. Access the APP1, APP2, RPM, VPWR, MAF, TP_REL and VSS PIDs. Drive the vehicle with monitoring PIDs. Are PIDs within specifications? (See PCM INSPECTION [L8, LF, L5].)	Yes	Go to the next step.
No	APP1, APP2 PIDs: Inspect if the output signal from the APP sensor changes smoothly. RPM PID: Inspect the CKP sensor and related wiring harness for vibration or an intermittent open/short circuit. VPWR PID: Inspect for an intermittent open circuit. MAF PID: Inspect for an intermittent open circuit of the MAF sensor and the related wiring harness. TP_REL PID: Inspect if the output signal from the TP sensor changes smoothly. VSS PID: Inspect for an intermittent open circuit in the VSS and related wiring harness.
5	Visually inspect the CKP sensor and teeth of the crankshaft pulley. (See CRANKSHAFT POSITION (CKP) SENSOR INSPECTION [L8, LF, L5].) Are the CKP sensor and teeth of the crankshaft pulley normal?	Yes	Go to the next step.
No	Replace the malfunctioning part.
6	Inspect the spark plug conditions. (See SPARK PLUG INSPECTION [L8, LF, L5].) Are the spark plug wet, covered with carbon or grayish white?	Yes	Spark plug is wet or covered with carbon: Inspect for fuel leakage from the fuel injector. 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 the PCV valve. (See POSITIVE CRANKCASE VENTILATION (PCV) VALVE REMOVAL/INSTALLATION [L8, LF, L5].)
8	Perform the electronic throttle control system operation inspection. (See ENGINE CONTROL SYSTEM OPERATION INSPECTION [L8, LF, L5].) Does the electronic throttle control system function properly?	Yes	Go to the next step.
No	Repair or replace the malfunctioning part according to electronic throttle system operation inspection results.
9	Visually inspect for deformed exhaust system parts. Are there any deformed exhaust system parts?	Yes	Replace the suspected part.
No	Go to the next step.
10	Inspect the fuel line pressure. (See FUEL LINE PRESSURE INSPECTION [L8, LF, L5].) Is the fuel line pressure correct?	Yes	Go to the next step.
No	Zero or low: Inspect the fuel pump relay and the fuel pump circuit. Inspect the fuel line for clogging. If there is no malfunction, replace the fuel pump unit. (See FUEL PUMP UNIT REMOVAL/INSTALLATION [L8, LF, L5].) High: Replace the fuel pump unit. (See FUEL PUMP UNIT REMOVAL/INSTALLATION [L8, LF, L5].)
11	Visually inspect for fuel leakage at the fuel injector O-ring and fuel line. Service if necessary. Is the fuel line pressure held after the ignition is off? (See FUEL LINE PRESSURE INSPECTION [L8, LF, L5].)	Yes	Go to the next step.
No	Inspect the fuel injector. (See FUEL INJECTOR INSPECTION [L8, LF, L5].) If the fuel injector is normal, replace the fuel pump unit. (See FUEL PUMP UNIT REMOVAL/INSTALLATION [L8, LF, L5].)
12	Note • The following test is for an engine stall with the A/C on. If other symptoms exist, go to the next step. Connect a pressure gauge to the A/C low and high pressure side lines. Turn the A/C on and measure the low side and high side pressure. Are the pressures within the specifications? (See REFRIGERANT PRESSURE CHECK.)	Yes	Go to the next step.
No	If the 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, L5].) For other symptoms, inspect the following: • Refrigerant charging amount • Condenser fan operation
13	Note • The following test should be performed for symptoms with the cruise control on. If other symptoms exist, go to the next step. Inspect the cruise control system. Is the cruise control system normal?	Yes	Go to the next step.
No	Repair or replace the malfunctioning part.
14	Inspect the A/F sensor. (See AIR FUEL RATIO (A/F) SENSOR, HEATED OXYGEN SENSOR (HO2S) INSPECTION [L8, LF, L5].) Is the A/F sensor normal?	Yes	Go to the next step.
No	Inspect for followings: • Exhaust gas leakage between exhaust manifold and A/F sensor. • Loose installation of A/F sensor. If there are no malfunctions detected, replace the A/F sensor. If there are malfunctions detected, repair or replace malfunctioning part. (See EXHAUST SYSTEM REMOVAL/INSTALLATION [L8, LF, L5].)
15	Inspect the evaporative purge hose between the fuel tank and the purge solenoid valve. Does the fuel flow into the evaporative purge hose?	Yes	Inspect the check valve. (See EVAPORATIVE GAS CHECK VALVE (ONE-WAY) INSPECTION [L8, LF, L5].)
No	Go to the next step.
16	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	Go to the next step. Inspect if the purge solenoid valve is stuck open mechanically. Inspect the evaporative emission control system.
No	Go to the next step.
17	Visually inspect the CMP sensor and teeth of the camshaft. (See CAMSHAFT POSITION (CMP) SENSOR INSPECTION [L8, LF, L5].) Are the CMP sensor and teeth of the camshaft normal?	Yes	Go to the next step.
No	Replace the malfunctioning part.
18	Inspect the variable tumble control operation. (See ENGINE CONTROL SYSTEM OPERATION INSPECTION [L8, LF, L5].) Is the variable tumble control normal?	Yes	Go to the next step.
No	Repair or replace the malfunctioning part.
19	Inspect the EGR system. (See ENGINE CONTROL SYSTEM OPERATION INSPECTION [L8, LF, L5].) Is the EGR system normal?	Yes	Go to the next step.
No	Replace the malfunctioning part.
20	Is the engine compression correct? (See COMPRESSION INSPECTION [L8, LF, L5].)	Yes	Inspect the following: • Valve timing • Internal transaxle part (ATX) • Clutch (MTX) • EGR valve (mechanical stuck) • Engine mounts • Check valve (two-way)
No	Inspect for cause.
21	• Verify test results. ― If normal, return to the diagnostic index to service any additional symptoms. (See SYMPTOM DIAGNOSTIC INDEX [L8, LF, L5].) ― If the malfunction remains, inspect the related Service Information and perform repair or diagnosis. • If the vehicle is repaired, troubleshooting is completed. • If the vehicle is not repaired or additional diagnostic information is not available, replace the PCM. (See PCM REMOVAL/INSTALLATION [L8, LF, L5].)

STEP

INSPECTION

RESULTS

ACTION

Verify the following:

• Vacuum connection

• Air cleaner element

• No air leakage from intake air system

• No restriction of the intake air system

• Proper sealing of intake manifold and components attached to intake manifold: such as EGR valve

• Ignition wiring

• Fuel quality (such as proper octane, contamination, winter/summer blend)

• Electrical connections

• Smooth operation of the throttle valve

Are all the items normal?

Yes

Go to the next step.

Service if necessary.

Repeat Step 1.

Connect the M-MDS to the DLC-2.

Switch the ignition to ON (Engine off).

Retrieve any DTCs.

Are there any DTCs displayed?

Yes

DTC is displayed:

Go to the appropriate DTC inspection.

(See DTC TABLE [L8, LF, L5].)

No DTC is displayed:

Go to the next step.

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, L5].)

Go to the next step.

Connect the M-MDS to the DLC-2.

Access the APP1, APP2, RPM, VPWR, MAF, TP_REL and VSS PIDs.

Drive the vehicle with monitoring PIDs.

Are PIDs within specifications?

(See PCM INSPECTION [L8, LF, L5].)

Yes

Go to the next step.

APP1, APP2 PIDs:

Inspect if the output signal from the APP sensor changes smoothly.

RPM PID:

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

VPWR PID:

Inspect for an intermittent open circuit.

MAF PID:

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

TP_REL PID:

Inspect if the output signal from the TP sensor changes smoothly.

VSS PID:

Inspect for an intermittent open circuit in the VSS and related wiring harness.

Visually inspect the CKP sensor and teeth of the crankshaft pulley.

(See CRANKSHAFT POSITION (CKP) SENSOR INSPECTION [L8, LF, L5].)

Are the CKP sensor and teeth of the crankshaft pulley normal?

Yes

Go to the next step.

Replace the malfunctioning part.

Inspect the spark plug conditions.

(See SPARK PLUG INSPECTION [L8, LF, L5].)

Are the spark plug wet, covered with carbon or grayish white?

Yes

Spark plug is wet or covered with carbon:

Inspect for fuel leakage from the fuel injector.

Spark plug is grayish white:

Inspect the fuel injector for clogging.

Install the spark plugs on original cylinders.

Go to the next step.

Remove and shake the PCV valve.

Does the PCV valve rattle?

Yes

Go to the next step.

Replace the PCV valve.

(See POSITIVE CRANKCASE VENTILATION (PCV) VALVE REMOVAL/INSTALLATION [L8, LF, L5].)

Perform the electronic throttle control system operation inspection.

(See ENGINE CONTROL SYSTEM OPERATION INSPECTION [L8, LF, L5].)

Does the electronic throttle control system function properly?

Yes

Go to the next step.

Repair or replace the malfunctioning part according to electronic throttle system operation inspection results.

Visually inspect for deformed exhaust system parts.

Are there any deformed exhaust system parts?

Yes

Replace the suspected part.

Go to the next step.

Inspect the fuel line pressure.

(See FUEL LINE PRESSURE INSPECTION [L8, LF, L5].)

Is the fuel line pressure correct?

Yes

Go to the next step.

Zero or low:

Inspect the fuel pump relay and the fuel pump circuit.

Inspect the fuel line for clogging.

If there is no malfunction, replace the fuel pump unit.

(See FUEL PUMP UNIT REMOVAL/INSTALLATION [L8, LF, L5].)

High:

Replace the fuel pump unit.

(See FUEL PUMP UNIT REMOVAL/INSTALLATION [L8, LF, L5].)

Visually inspect for fuel leakage at the fuel injector O-ring and fuel line.

Service if necessary.

Is the fuel line pressure held after the ignition is off?

(See FUEL LINE PRESSURE INSPECTION [L8, LF, L5].)

Yes

Go to the next step.

Inspect the fuel injector.

(See FUEL INJECTOR INSPECTION [L8, LF, L5].)

If the fuel injector is normal, replace the fuel pump unit.

(See FUEL PUMP UNIT REMOVAL/INSTALLATION [L8, LF, L5].)

Note

• The following test is for an engine stall with the A/C on. If other symptoms exist, go to the next step.

Connect a pressure gauge to the A/C low and high pressure side lines.

Turn the A/C on and measure the low side and high side pressure.

Are the pressures within the specifications?

(See REFRIGERANT PRESSURE CHECK.)

Yes

Go to the next step.

If the 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, L5].)

For other symptoms, inspect the following:

• Refrigerant charging amount

• Condenser fan operation

Note

• The following test should be performed for symptoms with the cruise control on. If other symptoms exist, go to the next step.

Inspect the cruise control system.

Is the cruise control system normal?

Yes

Go to the next step.

Repair or replace the malfunctioning part.

Inspect the A/F sensor.

(See AIR FUEL RATIO (A/F) SENSOR, HEATED OXYGEN SENSOR (HO2S) INSPECTION [L8, LF, L5].)

Is the A/F sensor normal?

Yes

Go to the next step.

Inspect for followings:

• Exhaust gas leakage between exhaust manifold and A/F sensor.

• Loose installation of A/F sensor.

If there are no malfunctions detected, replace the A/F sensor.

If there are malfunctions detected, repair or replace malfunctioning part.

(See EXHAUST SYSTEM REMOVAL/INSTALLATION [L8, LF, L5].)

Inspect the evaporative purge hose between the fuel tank and the purge solenoid valve.

Does the fuel flow into the evaporative purge hose?

Yes

Inspect the check valve.

(See EVAPORATIVE GAS CHECK VALVE (ONE-WAY) INSPECTION [L8, LF, L5].)

Go to the next step.

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

Go to the next step.

Inspect if the purge solenoid valve is stuck open mechanically.

Inspect the evaporative emission control system.

Go to the next step.

Visually inspect the CMP sensor and teeth of the camshaft.

(See CAMSHAFT POSITION (CMP) SENSOR INSPECTION [L8, LF, L5].)

Are the CMP sensor and teeth of the camshaft normal?

Yes

Go to the next step.

Replace the malfunctioning part.

Inspect the variable tumble control operation.

(See ENGINE CONTROL SYSTEM OPERATION INSPECTION [L8, LF, L5].)

Is the variable tumble control normal?

Yes

Go to the next step.

Repair or replace the malfunctioning part.

Inspect the EGR system.

(See ENGINE CONTROL SYSTEM OPERATION INSPECTION [L8, LF, L5].)

Is the EGR system normal?

Yes

Go to the next step.

Replace the malfunctioning part.

Is the engine compression correct?

(See COMPRESSION INSPECTION [L8, LF, L5].)

Yes

Inspect the following:

• Valve timing

• Internal transaxle part (ATX)

• Clutch (MTX)

• EGR valve (mechanical stuck)

• Engine mounts

• Check valve (two-way)

Inspect for cause.

• Verify test results.

― If normal, return to the diagnostic index to service any additional symptoms.

(See SYMPTOM DIAGNOSTIC INDEX [L8, LF, L5].)

― If the malfunction remains, inspect the related Service Information and perform repair or diagnosis.

• If the vehicle is repaired, troubleshooting is completed.

• If the vehicle is not repaired or additional diagnostic information is not available, replace the PCM.

(See PCM REMOVAL/INSTALLATION [L8, LF, L5].)