Engine Controls - Adjustments: Other Mazda MX-5 NA

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. No adjustments are required.

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 (Miata only). Rotate distributor or CAS until timing marks are aligned. Tighten lock bolt.

MIATA, MX-3, MX-6, PROTEGE, RX7, 323, 626 & 929

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 8)
2. Connect timing light. Set timing to specification (except RX7). See «IGNITION TIMING SPECIFICATIONS»(ref-18257-S20714365092000123000000) table. see scheme 1 On RX7, if ignition timing is not within specifications, see TESTS W/O CODES and appropriate TESTS W/CODES articles. Disconnect diagnostic tester or jumper wire from diagnostic connector.

Scheme 8

MPV

Connect jumper wire between ground and Green test connector in left front corner of engine compartment. (Scheme 9)or (Scheme 10). Connect timing light. Set timing to specification. See IGNITION TIMING SPECIFICATIONS table. see scheme 1 Remove jumper wire.

NAVAJO

1. Engine is equipped with a distributorless ignition. Base (initial) timing is preset at 10 degrees BTDC and is not adjustable. To check base timing, turn ignition off.
2. Disconnect SPOUT in-line connector in Yellow/Light Green wire near Ignition Control Module (ICM), in right front corner of engine compartment. Start engine.
3. Connect timing light and check timing. If ignition timing is not at 10 degrees BTDC, see TESTS W/O CODES and appropriate TESTS W/CODES articles. Turn off engine. Connect SPOUT in-line connector.

Scheme 9

Scheme 10

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.

COLD (FAST) IDLE SPEED

Note. For adjustments of the choke unloader, fast idle cam (static adjustment) and secondary throttle valve, see information in N - REMOVE/INSTALL/OHAUL article.

RX7

1. With engine cold, ensure roller near screw "B" is centered on fast idle cam. (Scheme 11) Warm engine to operating temperature. At 130-149°F (55-65°C), wax rod should extend fully and fast idle cam should separate from roller. If wax rod does not operate as described, replace wax rod or adjust separation point.
2. Turn screw "B" until separation point is as described in step 1). (Scheme 12) To adjust fast idle cam opening, turn screw "A". Using screw "A", align points on fast idle cam with roller at corresponding temperature. See FAST IDLE CAM OPENING SPECIFICATIONS (RX7) table.

FAST IDLE CAM OPENING SPECIFICATIONS

Scheme 11

Scheme 12

DASHPOT

Note. Before adjusting dashpot, warm engine to normal operating temperature. Turn off all accessories. Place transmission in Neutral (M/T) or Park (A/T).

Miata, MPV 3.0L, MX-3 1.6L, Protege, RX7 & 323

Operate engine at 4000 RPM. Slowly decrease engine RPM until throttle lever contacts dashpot. If engine RPM is not as specified when throttle lever contacts dashpot, loosen lock nut and adjust dashpot as necessary. See DASHPOT SPECIFICATIONS table. Tighten lock nut.

DASHPOT SPECIFICATIONS

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 .

Miata, MX-3, MX-6, Protege, 323, 626 & 929

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 8) 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»(ref-18257-S02397269692000123000000) table. Disconnect jumper wire.

1. Connect jumper wire between ground and Green 1-pin test connector in left front corner of engine compartment. (Scheme 9)or (Scheme 10). On 2.6L, connect tachometer to White 1-pin test connector in left front corner of engine compartment. On 3.0L, connect tachometer to test connector at ignition coil (White wire).
2. On all models, if idle speed is not within specification, rotate idle air adjusting screw on throttle body. See «IDLE SPEED SPECIFICATIONS»(ref-18257-S02397269692000123000000) table. Disconnect jumper wire.

Note. On Navajo, idle speed is computer controlled and is not adjustable. However, use the following initial throttle angle adjustment procedure (minimum air rate setting) as a basis for diagnosing idle speed problems or if throttle stop screw has been incorrectly set.

1. Ensure the following conditions exist: throttle bore, throttle plate and Idle Speed Control (ISC) air by-pass valve are free of contamination, oxygen sensor is free of contamination and is operating, throttle stop lever is resting against throttle stop screw, no vacuum leaks are present, cooling system is full, and ignition timing is set to specification.
2. Perform a thorough basic inspection and Self-Test (KOEO, KOER and continuous memory) to confirm operation of sub-systems which may contribute to idle speed control problems. See appropriate information in TESTS W/CODES article.
3. With engine off, disconnect negative battery cable for at least 5 minutes. Connect negative battery cable. Start engine and allow idle speed to stabilize for 2 minutes. Snap throttle open and return to idle. Lightly press and release accelerator. Turn engine off. Disconnect ISC air by-pass solenoid. NOTE: If engine RPM fluctuates during idle, throttle plate may be open enough to allow canister purge flow. To verify this condition, disconnect and plug canister purge line. If purge is present, close throttle plate until fluctuations stop.
4. Start engine. Operate engine at 2500 RPM for 30 seconds. Allow engine to idle for 2 minutes. Turn throttle stop screw until engine idles at 675 RPM.
5. Turn off engine. Repeat step 4). Turn off engine. Disconnect negative battery cable for at least 5 minutes. Connect ISC air by-pass solenoid connector. Connect negative battery cable. Verify throttle plate is not stuck in bore and linkage is not preventing throttle stop lever from contacting throttle stop.
6. Start engine and allow to idle for 2 minutes. Snap throttle open and return to idle. Lightly press and release accelerator. Allow engine to idle. If engine does not idle properly, see TESTS W/O CODES article.

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 8) Connect tachometer to diagnostic connector terminal IG (-).
2. If idle speed is not within specification, rotate air adjusting screw on throttle body. (Scheme 13) See «IDLE SPEED SPECIFICATIONS»(ref-18257-S02397269692000123000000) table. If idle speed is too high with air adjusting screw closed, turn throttle adjusting screw. Disconnect jumper wire.

Scheme 13

IDLE SPEED SPECIFICATIONS

Except B2200 (Carbureted)

Air/fuel mixture is computer controlled and cannot be manually adjusted. If CO level is excessive, see TESTS W/O CODES article.

Scheme 14

Scheme 15

Note. TP sensor is not adjustable. Replace TP sensor if voltage readings are not within specification.

1. Ensure throttle linkage is not preventing throttle stop lever from contacting throttle stop screw. Disconnect Electronic Control Assembly (ECA) 60-pin connector. Inspect connector for damaged pins, corrosion or loose wires and repair as necessary.
2. Connect Breakout Box (T83L-50-EEC-IV) between ECA and ECA harness. Connect digital voltmeter positive lead to pin No. 47 and negative lead to pin No. 46 of breakout box.
3. Turn ignition on. Observe voltmeter while slowly moving throttle between fully closed and wide open positions. Voltage should be .60 volt with throttle fully closed and about 4.50 volts throttle fully open.
4. If voltages values are not as specified, ensure throttle angle (minimum air rate) is correct. See «IDLE SPEED»(ref-18257-S26655033242000123000000) under IDLE SPEED & MIXTURE. If throttle angle is correct, remove TP sensor.
5. Check for damaged, corroded or misadjusted pins. If pins are okay, install TP sensor. Check voltage readings again. If voltage readings are not as specified, perform KOEO self-test. See information G - TEST W/ CODES article. If KOEO self-test indicates no problems, replace TP sensor.

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.