Diagnostic procedure

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

EXHAUST SMOKE - DIAGNOSTIC PROCEDURE

STEP	INSPECTION		ACTION
1	What color is smoke coming from exhaust system?	Blue	Burning oil is indicated. Go to next step.
		White	Water in combustion is indicated. Go to Step 3.
		Black	Rich fuel mixture is indicated. Go to Step 4.
2	Remove and shake PCV valve. Does PCV valve rattle?	Yes	Inspect for following: Damaged valve guide, stems or valve seals Blocked oil drain passage in cylinder head Piston rings are not seated, seized or worn. Damaged cylinder bore If other driveability symptoms are present, return to diagnostic index to service any additional symptoms.
2	Remove and shake PCV valve. Does PCV valve rattle?	No	Replace PCV valve.
3	Does cooling system hold pressure?	Yes	Inspect for following: Cylinder head gasket leakage Intake manifold gasket leakage Engine block cracks or porosity If other driveability symptoms are present, return to diagnostic index to service any additional symptoms.
3	Does cooling system hold pressure?	No	Inspect for cause.
4	Inspect for following: Air cleaner restriction Collapsed or restricted intake-air system Restricted fuel return line Are all items okay?	Yes	Go to next step.
4		No	Service as necessary. Repeat Step 4.
5	Connect WDS or equivalent to DLC-2. Turn ignition switch on. Retrieve any DTC. Is "PASSED" displayed?	Yes	No DTC displayed: Go to next step.
5		No	DTC displayed: Go to appropriate DTC test.
6	Install fuel pressure gauge between fuel filter and fuel distributor. Start engine and run it at idle. Measure fuel line pressure at idle. Is fuel line pressure correct at idle? Fuel line pressure 420-460 kPa {4.3-4.6 kgf/cm2, 61-66 psi}	Yes	Go to next step.
6		No	Zero or low: Inspect fuel pump circuit Inspect for open fuel pump relief valve Inspect for fuel leakage inside pressure regulator Inspect for clogged main fuel line High: Inspect pressure regulator for high pressure cause Inspect for clogged fuel return line
7	Perform spark test. (See SPARK TEST .) Is strong blue spark visible at each cylinder?	Yes	Inspect spark plugs and CMP sensor.
7		No	Repair or replace malfunctioning part according to spark test results.
8	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 is not available, replace or reprogram PCM.