NO.27 SPARK PLUG CONDITION [YF (2.0L Zetec)]


27	SPARK PLUG CONDITION
DESCRIPTION	Incorrect spark plug condition
POSSIBLE CAUSE	Note • Spark plugs inspection can determine whether the problem is related to a specific cylinder or to all cylinders. Wet/carbon stuck on specific plug: • Spark-Weak, not visible • Air/fuel mixture-Excessive fuel injection volume • Compression-No compression, low compression • Malfunctioning spark plug Grayish white with specific plug: • Air/fuel mixture-Insufficient fuel injection volume • Malfunctioning spark plug Wet/carbon is stuck on all plugs: • Spark-Weak spark • Air/fuel mixture-Too rich • Compression-Low compression • Clogging in intake/exhaust system Grayish white with all plugs: • Air/fuel mixture-Too lean Warning The following troubleshooting flow chart contains fuel system diagnosis and repair procedures. Read the following warnings before performing any fuel system-related procedures: • 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 [YF (2.0L Zetec)].) (See AFTER SERVICE PRECAUTION [YF (2.0L Zetec)].) Caution • Disconnecting/connecting quick release connectors without cleaning them may possibly cause damage to the fuel pipe or 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	Remove all the spark plugs. Inspect spark plug condition. Is spark plug condition normal?	Yes	Troubleshooting completed.
1		No	Specific plug is wet or covered with carbon: Go to the next step. Specific plug looks grayish white: Go to Step 7. All plugs are wet or covered with carbon: Go to Step 9. All plugs look grayish white: Go to Step 15.
2	Are the spark plugs wet/covered with carbon due to engine oil?	Yes	Inspect all areas related to oil, working up and down.
2		No	Go to the next step.
3	Inspect the spark plug for the following: • Cracked insulator • Heat range • Air gap • Worn electrode Is the spark plug normal?	Yes	Go to the next step.
3		No	Replace the spark plug. (See SPARK PLUG REMOVAL/INSTALLATION [YF (2.0L Zetec)].)
4	Inspect the compression pressure at the suspected malfunctioning cylinder. Is the compression pressure correct?	Yes	Go to the next step.
4		No	Repair or replace the malfunctioning part.
5	Install all spark plugs. Perform the spark test at the suspected malfunctioning cylinder. Is a strong blue spark visible? (Compare with the normal cylinder.)	Yes	Go to the next step.
5		No	Repair or replace the malfunctioning part.
6	Perform the fuel line pressure inspection. Is the fuel line pressure correct?	Yes	Inspect the fuel injector for the following: • Open or short circuit in injector • Leakage • Injection volume
6		No	Zero or low: Inspect the fuel pump, IFS switch, and fuel pump relay-related circuit. Inspect the fuel line for clogging. • If there is no malfunction, replace the fuel pump unit. (See FUEL PUMP UNIT REMOVAL/INSTALLATION [YF (2.0L Zetec)].) High: Replace the fuel pump unit. (See FUEL PUMP UNIT REMOVAL/INSTALLATION [YF (2.0L Zetec)].)
7	Inspect the spark plug for following. • Heat range • Air gap Is the spark plug normal?	Yes	Go to the next step.
7		No	Replace the spark plug.
8	Remove the suspected fuel injector. Inspect the following: • Resistance (See FUEL INJECTOR INSPECTION [YF (2.0L Zetec)].) • Fuel injection volume (See FUEL INJECTOR INSPECTION [YF (2.0L Zetec)].) Are all the above items normal?	Yes	Inspect for open circuit in the wiring harness between the fuel injector terminal and the following PCM terminals: • For No.1 cylinder: 70 • For No.2 cylinder: 96 • For No.3 cylinder: 20 • For No.4 cylinder: 95
8		No	Replace the fuel injector.
9	Is the air cleaner element free of restrictions?	Yes	Go to the next step.
9	Is the air cleaner element free of restrictions?	No	Replace the air cleaner element.
10	Perform the spark test. (See FUEL LINE PRESSURE INSPECTION [YF (2.0L Zetec)].) Is a strong blue spark visible at each cylinder?	Yes	Go to the next step.
10		No	Repair or replace the malfunctioning part.
11	Perform the fuel line pressure inspection. Is the fuel line pressure correct? (See FUEL LINE PRESSURE INSPECTION [YF (2.0L Zetec)].)	Yes	Go to the next step.
11		No	Zero or low: Inspect the fuel pump and fuel pump relay elated circuit. Inspect the fuel line for clogging. • If there is no malfunction, replace the fuel pump unit. (See FUEL PUMP UNIT REMOVAL/INSTALLATION [YF (2.0L Zetec)].) High: Replace the fuel pump unit. (See FUEL PUMP UNIT REMOVAL/INSTALLATION [YF (2.0L Zetec)].)
12	Inspect the following PIDs. • ECT • O2S11 (When engine can be started) • O2S12 (When engine can be started) • MAF (See PCM INSPECTION [YF (2.0L Zetec)].) Are the PIDs normal?	Yes	Go to the next step.
12		No	Repair or replace the malfunctioning part.
13	Perform the purge control inspection. (When engine can be started) (See Purge Control System Inspection.) Is the purge control correct?	Yes	Go to the next step.
13		No	Repair or replace the malfunctioning part.
14	Perform the compression inspection. Is compression correct?	Yes	Visually inspect for deformed in exhaust system part.
14		No	Repair or replace the malfunctioning part.
15	When the engine cannot be started, inspect intake-air system for air leakage. When the engine can be started, perform the intake manifold vacuum inspection. Is air sucked in from the intake-air system?	Yes	Repair or replace the malfunctioning part.
15		No	Go to the next step.
16	Perform the fuel line pressure inspection. Is the fuel line pressure correct? (See FUEL LINE PRESSURE INSPECTION [YF (2.0L Zetec)].)	Yes	Inspect the following PIDs. • ECT • O2S11 • O2S12 • MAF (See PCM INSPECTION [YF (2.0L Zetec)].) Inspect PCM GND condition.
16		No	Zero or low: Inspect the fuel pump, IFS switch and fuel pump relay related circuit. Inspect the fuel line for clogging. • If there is no malfunction, replace the fuel pump unit. (See FUEL PUMP UNIT REMOVAL/INSTALLATION [YF (2.0L Zetec)].) High: Replace the fuel pump unit. (See FUEL PUMP UNIT REMOVAL/INSTALLATION [YF (2.0L Zetec)].)
17	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)].)