Engine Controls - Adjustments Mazda 929 HD

ENGINE MECHANICAL

Before performing any on-vehicle adjustments to fuel or ignition systems, ensure engine mechanical condition is okay.

VALVE CLEARANCE

Note. All piston engines are equipped with hydraulic valve lash adjusters. Valve clearance is not adjustable. Hydraulic lash adjuster must be in a collapsed position to check clearance.

IGNITION TIMING

Note. Before adjusting ignition timing, warm engine to normal operating temperature. Turn off all accessories. Place transmission in Neutral (M/T) or Park (A/T). Ensure idle speed is correct. See IDLE SPEED under IDLE SPEED & MIXTURE. If timing is not within specification, loosen distributor or Crank Angle Sensor (CAS) lock bolt. Rotate distributor or CAS until timing marks are aligned. Tighten lock bolt.

Scheme 1

1. Connect Diagnostic Tester (49 B019 9A0) to diagnostic connector and select SELF-TEST mode (position 1), or connect jumper wire between diagnostic connector terminals TEN and GND. (Scheme 2)
2. Connect timing light. Set timing to specification. See «IGNITION TIMING SPECIFICATIONS»(/mazda/929/hd-1993-1995/remont/adjustments/#engine-controls-adjustments) table. (Scheme 1)

Scheme 2

IGNITION TIMING SPECIFICATIONS

IDLE SPEED & MIXTURE

Note. Mixture adjustment is NOT a normal tune-up procedure. DO NOT adjust mixture unless mixture control unit is replaced or vehicle fails emissions test.

Note. Idle mixture is not adjustable. If idle mixture is incorrect, see TESTS W/CODES article in the ENGINE PERFORMANCE section.

IDLE SPEED

Note. Before adjusting idle speed, warm engine to normal operating temperature. Turn off all accessories. Place transmission in Neutral (M/T) or Park (A/T). Ensure ignition timing is adjusted. See IGNITION TIMING.

1. Connect Diagnostic Tester (49 B019 9A0) to diagnostic connector and select SELF-TEST mode, or connect jumper wire between diagnostic connector terminals TEN and GND. (Scheme 2) Connect tachometer to diagnostic connector terminal IG (-).
2. If idle speed is not within specification, rotate idle air adjusting screw on throttle body. See IDLE SPEED SPECIFICATIONS table. Disconnect jumper wire.

IDLE SPEED SPECIFICATIONS

INSPECTION

Disconnect TP sensor connector. Using an ohmmeter, measure resistance between specified terminals of TP sensor connector. See TP SENSOR RESISTANCE table. (Scheme 3) If resistance is not as specified, adjust TP sensor. See ADJUSTMENT procedure.

1. Insert a feeler gauge of specified thickness between throttle lever and throttle stop screw. See TP SENSOR ADJUSTMENT table. Check continuity between TP sensor connector terminals "C" and "D". (Scheme 3)
2. If continuity is not as specified, loosen TP sensor mounting screws. Rotate TP sensor until continuity is as specified. Tighten mounting screws. Connect TP sensor connector.

TP SENSOR RESISTANCE

TP SENSOR ADJUSTMENT

Scheme 3

THROTTLE (IDLE) SWITCH

Note. Throttle switch is either a part of TP sensor, which is adjusted automatically when TP is adjusted, or a separate, nonadjustable switch on throttle body. See THROTTLE POSITION (TP) SENSOR.

See also:
• TESTS W/CODES
• IGNITION TIMING SPECIFICATIONS