Diagnostic procedure

WARNING: This page is about a different car, the 2005 Mazda 6. However, it is still accessible from the selected car via links, so may be relevant.

NO. 4 HARD START/LONG CRANK/ERRATIC START/ERRATIC CRANK [AJ] DIAGNOSTIC PROCEDURE

STEP	INSPECTION		ACTION
1	Inspect for the following: Vacuum leakage Proper fuel quality (e.g. proper octane, contamination, winter/summer blend) Loose bands on intake-air system Cracks on intake-air system parts Air cleaner restriction Are all items okay?	Yes	Go to the next step.
1		No	Service as necessary. Repeat Step 1.
2	Connect WDS or equivalent to DLC-2. Turn ignition switch to ON position. Retrieve any DTCs. Are there any DTCs displayed?	Yes	DTC is displayed: Go to appropriate DTC test.
2		No	No DTC is displayed: Go to the next step.
3	Is engine overheating?	Yes	Go to flowchart "NO. 17 COOLING SYSTEM CONCERNS-OVERHEATING ".
3	Is engine overheating?	No	Go to the next step.
4	Inspect ignition coil related harnesses condition (intermittent open or short circuit) for all cylinders. Are all harnesses condition okay?	Yes	Go to the next step.
4		No	Repair suspected wiring harness.
5	Inspect spark plug conditions. Is spark plug wet, covered with carbon or grayish white?	Yes	Spark plug is wet or covered with carbon: Inspect for fuel leakage from fuel injector. Spark plug is grayish white: Inspect for clogged fuel injector.
5		No	Install spark plugs on original cylinders. Go to the next step.
6	Visually inspect CKP sensor and teeth of crankshaft pulley. Are CKP sensor and teeth of crankshaft pulley okay?	Yes	Go to the next step.
6		No	Replace malfunctioning part.
7	Remove and shake PCV valve. Does PCV valve rattle?	Yes	Go to the next step.
7	Remove and shake PCV valve. Does PCV valve rattle?	No	Replace PCV valve.
8	Install fuel pressure gauge between pulsation damper and fuel distributor. Short check connector terminal F/P to body GND using a jumper wire. (See AFTER REPAIR PROCEDURE .) Turn ignition switch to ON position (Engine OFF). Inspect fuel line pressure. (See FUEL LINE PRESSURE INSPECTION .) Is fuel line pressure correct?	Yes	Go to the next step.
8		No	Zero or low: Inspect fuel pump relay and fuel pump related circuit. Inspect for clogged fuel line. If okay, replace fuel pump unit. (See FUEL PUMP UNIT REMOVAL/INSTALLATION .) High: Replace fuel pump unit. (See FUEL PUMP UNIT REMOVAL/INSTALLATION .)
9	Attempt to start engine at part throttle. Does engine run smoothly at part throttle?	Yes	Inspect electronic throttle control system operation.
9		No	Go to the next step.
10	Is fuel line pressure held after ignition switch is turned to OFF position?	Yes	Go to the next step.
10		No	Inspect fuel injector. (See FUEL INJECTOR INSPECTION [AJ] .) If fuel injector is okay, replace fuel pump unit. (See FUEL PUMP UNIT REMOVAL/INSTALLATION .)
11	Disconnect vacuum hose from purge solenoid valve and plug opening end of vacuum hose. Attempt to start engine. Is starting condition improved?	Yes	Inspect if purge solenoid valve sticks open. (See PURGE SOLENOID VALVE INSPECTION .)
11		No	Go to the next step.
12	Inspect MAF sensor for contamination. (See MASS AIR FLOW (MAF) SENSOR INSPECTION .) Is there any contamination?	Yes	Replace MAF/IAT sensor.
12		No	Go to the next step.
13	Inspect for restriction in the exhaust system. Is there any restriction?	Yes	Inspect exhaust system.
13		No	Go to the next step.
14	Inspect engine condition while tapping EGR valve housing. Does engine condition improve?	Yes	Replace EGR valve. (See EGR VALVE REMOVAL/INSTALLATION [AJ] .)
14		No	Go to the next step.
15	Inspect starting system. (See STARTER INSPECTION .) (See STARTER INTERLOCK SWITCH INSPECTION (MTX) .) Is starting system normal?	Yes	Inspect for loose connectors or poor terminal contact. If okay, remove EGR valve and visually inspect for mechanically stuck EGR valve. (See EGR VALVE INSPECTION [AJ] .)
15		No	Repair or replace components as required.
16	Verify test results. If okay, return to diagnostic index to service any additional symptoms. If malfunction remains, inspect related Service Bulletins and/or On-line Repair Information and perform repair or diagnosis. If vehicle is repaired, troubleshooting completed. If vehicle is not repaired or additional diagnostic information is not available, reprogram PCM if later calibration is available. Retest.