NO.10 LOW IDLE/STALLS DURING DECELERATION [YF (2.0L Zetec)]


10	LOW IDLE/STALLS DURING DECELERATION
DESCRIPTION	• Engine stops unexpectedly at the beginning of deceleration or recovery from deceleration.
POSSIBLE CAUSE	• Vacuum leakage • IAC valve malfunction • Air leakage from intake-air system • Improper air/fuel mixture ratio control • Evaporative emission control system malfunction • TP sensor misadjustment • TP sensor or related circuit malfunction • MAF sensor or related circuit malfunction • Brake switch or related circuit malfunction • Neutral/clutch pedal position switch or related circuit malfunction (MTX) • TR switch or related circuit malfunction (ATX) • Improper A/C magnetic clutch operation


STEP	INSPECTION	RESULTS	ACTION
1	• Does the engine idle rough?	Yes	Go to symptom troubleshooting "No.8 Engine runs rough/rolling idle". (See NO.8 ENGINE RUNS ROUGH/ROLLING IDLE [YF (2.0L Zetec)].)
1	• Does the engine idle rough?	No	Go to the next step.
2	Turn off the A/C switch and fan switch. Does the A/C magnetic clutch engage?	Yes	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 [YF (2.0L Zetec)].)
2		No	Go to the next step.
3	Verify the following: • Proper routing and no damage of vacuum lines • IAC valve is connected properly. • No air leakage from intake-air system Are all items normal?	Yes	Go to the next step.
3		No	Service if necessary. Repeat Step 3.
4	Connect the WDS or equivalent to the DLC-2. Retrieve any continuous memory, KOEO and KOER DTCs using the WDS or equivalent. Are any DTCs displayed?	Yes	DTC is displayed: Go to the appropriate DTC inspection. (See DTC TABLE [YF (2.0L Zetec)].)
4		No	No DTC is displayed: Go to the next step.
5	Does the idle speed drop or stall when disconnecting the IAC valve?	Yes	Go to the next step.
5		No	Inspect the following: • Circuit from IAC valve to the PCM terminal 83 for open or short • Circuit from main relay terminal 87 to IAC valve for open or short • IAC valve for sticking If normal, go to the next step.
6	Disconnect the vacuum hose between the purge solenoid valve and the intake manifold from the purge solenoid valve side. Plug the open end of vacuum hose. Drive vehicle. Does the engine condition improve?	Yes	Inspect the evaporative emission control system.
6		No	Go to the next step.
7	Connect the WDS or equivalent to the DLC-2. Access the following PIDs. • TP • MAT • VSS • BOO • CPP (MTX) • CPP/PNP (MTX) • TR (ATX) Monitor each PID while driving the vehicle. (See PCM INSPECTION [YF (2.0L Zetec)].) Are the PIDs normal?	Yes	Intermittent concern exists. (See INTERMITTENT CONCERN TROUBLESHOOTING [YF (2.0L Zetec)].)
7		No	TP PID: Inspect the TP sensor. (See THROTTLE POSITION (TP) SENSOR INSPECTION [YF (2.0L Zetec)].) MAF PID: Inspect the MAF sensor. (See MASS AIR FLOW (MAF) SENSOR INSPECTION [YF (2.0L Zetec)].) VSS PID: Inspect the VSS. (See DTC TABLE [YF (2.0L Zetec)].) BOO PID: Inspect the brake switch. CPP PID: (MTX) Inspect the clutch pedal position switch. CPP/PNP PID: (MTX) Inspect the neutral switch. TR PID: (ATX) Inspect the TR switch. (SeeTRANSAXLE RANGE (TR) SWITCH INSPECTION [LA4AX-EL (CD4E)].)
8	Verify test results. • If normal, return to the diagnostic index to service any additional symptoms. (See ENGINE SYMPTOM TROUBLESHOOTING [YF (2.0L Zetec)].) • If any malfunction remains, inspect related service information and, repair or diagnosis accordingly. - If the vehicle is repaired, troubleshooting completed. - If the vehicle is not repaired or additional diagnostic information is not available, replace the PCM. (See PCM REMOVAL/INSTALLATION [YF (2.0L Zetec)].)