Mazda 3 Service Manual: Engine Tune Up [Mzr 2.0, Mzr 2.5]

NOTE:

• If the accelerator pedal is depressed continuously for a specified time, the engine speed may decrease to the idle speed. This is due to the fuel cut control operation, which prevents overheating, and it does not indicate a malfunction.

Engine Tune-up Preparation

1. Verify the following:

• MTX: Shift lever is in neutral position.

• ATX: Selector lever is in P or N position.

2. Warm up the engine to normal operating temperature.

a. Increase the engine speed to 2,500—3,000 rpm

until the cooling fan starts running.

b. When the cooling fan starts running, release the accelerator pedal and wait until the cooling fan stops running.

3. Turn off all electrical loads.

4. Connect the M-MDS to the DLC-2.

Idle Speed Inspection

NOTE:

• Idle speed is not adjustable.

• Idle speed verification requires M-MDS.

1. Complete the engine tune-up preparation..

2. Verify that the idle speed (M-MDS: RPM) is within the specification..

Idle speed (MTX: Neutral position, ATX: P, N position)

• 600—700 rpm (MTX), 650—750 (ATX)

Ignition Timing Inspection

NOTE:

• The ignition timing cannot be adjusted.

• The M-MDS is required to verify the ignition timing.

1. Complete the engine tune-up preparation..

2. Verify the ignition timing (M-MDS: SPARKADV) using the PID/data monitor function of the M-MDS..

Ignition timing

• MZR 2.0: Approx. BTDC 8°

• MZR 2.5: Approx. BTDC 12°

3. Verify that ignition timing advances when the engine speed increases gradually.

Idle Mixture Inspection

1. Verify that the idle speed and ignition timing are within the specification..

2. Insert an exhaust gas analyzer into the tailpipe.

3. Verify that the CO and HC concentrations are within regulation.

CO concentration

• Within the regulation

HC concentration

• Within the regulation

Idle-up Speed Control Inspection

NOTE:

• Idle speed is not adjustable.

• Idle speed verification requires M-MDS.

1. Complete the engine tune-up preparation..

2. Verify that the engine speed (M-MDS: RPM) is within the specification when each load is applied. (The speed decrease just after the load is applied is not considered.).

• If the engine speed is not within the specification when a specified load is applied, inspect the related input parts, wiring harnesses, and connectors.

Idle-up speed (MTX: Neutral position, ATX: P, N position)

• A/C on: 700—800 rpm (MTX), 650—770 (ATX)

• Electrical loads on: 650—800 rpm