engine MAZDA MX-5 1994 Workshop Manual

EXHAUST GAS RECIRCULATION (EGR) Operation Cold Engine (Coolant temperature less than 55°C (1 31 OF)) EGR operation is stopped to improve driveability when the engine temperature is cold. u Warm Engine The powertrain control module (engine) controls the solenoid valves (vacuum side and vent side) to sup- ply EGR gases as described below. Remark Operating condition Idle Deceleration High speed Heavy load EGR SOLENOID VALVE (VACUUM) I I EGR operation Acceleration Warming up Other SYSTEM OPERATION 1. Connect the SSTs to the PCME as shown. 2. Start the engine. 3. Drive the vehicle and verify that PCME terminals 1 R and 1 T voltage is battery positive voltage (B+) while the en- gine is still cold. 4. Warm up the engine to normal operating temperature and let it idle. 5. Drive the vehicle and verify that the Engine Signal Moni- tor green and red lamps flash when the SST is set to 1 R and 1 T. 6. Ground the PCME terminal IT by using a jumper wire. 7. Verify that the engine runs roughly or stalls at idle. Stopped EGR SOLENOID VALVE (VACUUM) Inspection 1. Disconnect the vacuum hoses. 2. Blow into the EGR solenoid valve (vacuum) and verify that air does not flow. 3. Disconnect the EGR solenoid valve (vacuum) connec- tor. 4. Apply battery positive voltage and a ground to the sole- noid valve as shown. 5. Blow through the EGR solenoid valve (vacuum) and verify that air flows. 6. If not as specified, replace the EGR solenoid valve (vac- uum) assembly. Idle switch: ON Above 3,125 rpm - Reduced EGR gas amount Control supply of EGR gas amount by using signal from EGR function sensor - Coolant temperature: Between 55OC (1 31 OF) and 60°C {140°F) - Gartner Banana

F EXHAUST GAS RECIRCULATION (EGR) VACUUM PUMP EGR SOLENOID VALVE (VENT) lnspection 1. Disconnect the vacuum hoses. 2. Blow through the EGR solenoid valve (vent) and verify u that air flows. 3. Disconnect the EGR solenoid valve (vent) connector. 4. Apply battery positive voltage and a ground to the EGR solenoid valve (vent) as shown. 5. Blow into the EGR solenoid valve (vent) and verify that air does not flow. 6. If not as specified, replace the EGR solenoid valve (vent) assembly. EGR FUNCTION SENSOR lnspection Output voltage inspection 1. Disconnect the PCME connector. 2. Connect the SST to the PCME as shown and connect a vacuum pump. 3. Turn the ignition switch to ON (engine OFF). 4. Measure voltage at the terminals as shown in the table. I I Vacuum I Terminal 5. If not correct at terminal 2J, check the wiring harness and 'i terminal 21 of the PCME. B A C Resistance 1. Disconnect the EGR function sensor connector, and connect an ohmmeter. 2. Disconnect the vacuum hose from the EGR control valve, and connect a vacuum pump. 3. Measure the resistance between the terminals as shown while vacuum is applied. PCME Specification 2K 2 D 2J Approx. 0 kPa {O mmHg, 0 inHg} 4. If not as specified, replace the EGR control valve. Approx. 20 kPa I150 mmHg, 5.9 inHg} 4.5--5.5 V OV Terminal LC A-C A-B Approx. 0.8 V Resistance 0.1-2.4 ki2 0.5-2.7 W1 Approx. 2.7 W1 Approx. 5 V Gartner Banana

EXHAUST GAS RECIRCULATION (EGR) EGR CONTROL VALVE I EGR CONTROL VALVE Inspection 1. Start the engine and let it idle. 2. Connect a vacuum pump as shown and apply vacuum. 3. Verify that the engine runs roughly or stalls at more than the specified vacuum. Specification: 5.4--12.0 kPa (40-90 mmHg, 1.6-3.5 inHg) 4. If not as specified, replace the EGR control valve. Replacement Plug the water hoses after disconnecting them. 1. Remove the EGR control valve in the sequence shown below. (1 ) EGR hoses (2) Vacuum hose (3) EGR function sensor connector (4) EGR control valve and gasket 2. Install a new gasket, and then install the EGR control valve in the reverse order of removal. Gartner Banana

F POSITIVE CRANKCASE VENTILATION (PCV) SYSTEM POSITIVE CRANKCASE VENTILATION (PCV) SYSTEM DESCRIPTION The PCV valve is operated by the intake manifold vacuum. 4 When the engine is running at idle the PCV valve is opened slightly and a small amount of blow by gas is drawn into the intake manifold to be burned. At higher engine speeds the PCV valve is opened further, allowing a larger amount of blow by gas to be drawn into the intake manifold. VENTILATION I PCV VALVE Inspection 1. Warm up the engine to the normal operating tempera- ture and run it at idle. 2. Disconnect the PCV valve together with the ventilation hose from the cylinder head cover. 3. Block the PCV valve opening. 4. Verify that vacuum is felt. 5. Remove the PCV valve. 6. Blow through the valve from port A and verify that air comes out of port B. 7. Blow through the valve from port B and verify that no air comes out of port A. 8. Replace the PCV valve if necessary. Gartner Banana

FUEL EVAPORATIVE SYSTEM FUEL EVAPORATIVE SYSTEM DESCRIPTION The fuel evaporative system consists of the fuel vapor valve, the two-way check valve, the charcoal can- ister, the purge solenoid valve, the powertrain control module (engine), and the input devices. The amount of evaporative fumes introduced into the engine and burned is controlled by the solenoid valve in relation to the engine's operating conditions. To maintain the best engine performance, the solenoid valve is controlled by the powertrab control module (engine). THROTTLE 1-1 POSITION SENSOR I1 I I (IDLE SWITCH) 7 BAROMETIC ABSOLUTE PRESSURE SENSOR PARWNEUTRAL SWITCH (AT) MASS AIRFLOW SENSOR CRANKSHAFT POSITION SENSOR (SGT-SIGNAL) n - DUTY - LOW HIGH (ENGINE) CHARCOAL PURGE SOLENOID VALVE CANISTER HEATED OXYGEN SENSOR ENGINE COOLANT POWERTRAIN TEMPERATURE SENSOR CONTROL MODULE CHECK VALVE # 11 FUEL VAPOR VALVE Operation The purge solenoid valve is controlled by duty signals from the powertrain control module (engine) to per- form purging of the charcoal canister. Purging is done when these conditions are met: i/ 1. After warm-up. 2. Driving in gear. 3. Accelerator pedal depressed (idle switch OFF). 4. Heated oxygen sensor functioning normally. Gartner Banana

FUEL EVAPORATIVE SYSTEM I GROUND I PURGE SOLENOID VALVE On-vehicle lnspection 1. Warm up the engine to normal operating temperature. 2. Run the engine at idle. d 3. Disconnect the vacuum hose from the purge solenoid valve and verify that no vacuum is felt at the purge sole- noid valve. 4. If not as specified, check the purge solenoid valve. lnspection 1. Disconnect the vacuum hoses from the purge solenoid valve. 2. Verify that no air flows through the purge solenoid valve. 3. Disconnect the purge solenoid valve connector and con- nect battery positive voltage and a ground to the termi- nals of the purge solenoid valve. 4. Verify that the air flows through the valve. 5. If not as specified, replace the purge solenoid valve. TWO-WAY CHECK VALVE lnspection 1. Remove the valve. 2. Check the operation of the valve with a vacuum pump. INSTALLATION DIRECTION Specification I Apply approx. 15 mmHg i0.59 inHg} vacuum at port A 1 Airflow I 1 Agply apgrox. 44 mmH~ (1.73 inHd vacuum at Port 6 1 Airflow 1 3. If not as specified, replace the two-way check valve. THREE-WAY CHECK VALVE lnspection 1. Remove the valve and plug the port C. 2. Check operation of the valve with a vacuum pump. Specification 3. If not as specified, replace the three-way check valve. Apply approx. 37 mmHg {I -46 inHg} vacuum at port A Apply approx. 70 mmHg (2.76 inHg} vacuum at port I3 Airflow Airflow -d Gartner Banana

AIC CUT-OFF CONTROL SYSTEM AIC CUT-OFF CONTROL SYSTEM DESCRIPTION An NC cut-off system is used to improve idle smoothness after just starting the engine and to improve - acceleration performance. IGNITION SWITCH POWERTRAIN CONTROL MODULE (ENGINE) CRANKSHAFT POSITION - I DETERMINA- TION OF NC CUT-OFF & $1 . 1 THROTTLE I POSITION SENSOR AIC RELAY IGNITION SWITCH SENSOR 7 After engine has been started - The AJC is cut-off for 2 sec. just after the engine is started. Acceleration The AIC is cut-off upon wide-open-throttle acceleration for approx. 5 sec. Gartner Banana

F A/C CUT-OFF CONTROL SYSTEM D B AIC RE LAY SYSTEM INSPECTION 1. Turn the ignition switch ON. 2. Turn the blower switch and air conditioning sensor ON. 3. Start the engine. d 4. Verify that the A/C stops for approx. 2 sec. after the en- gine start. 5. Rotate the throttle link to fully open position. 6. Verify that the A/C stops for approx. 5 sec. after the throttle link to fully open position. 7. If not specified, inspect as following. PCME 1Q terminal voltage A/C relay Throttle position sensor AIC RELAY Inspection 1. Remove the A/C relay. 2. Check the continuity between the terminals of the relay. 3. If not specified, replace the A/C relay. B+: Battery positive voltage Terminal A - B Apply B+ B+ not applied Terminal C - D Yes No Gartner Banana

DECHOKE CONTROL SYSTEM DECHOKE CONTROL SYSTEM DESCRIPTION To clean out excess fuel in cylinders, as in the case of engine flooding, when the engine is cold, no fuel will be injected when the accelerator is held fully depressed while cranking the engine. CRANKSHAFT POSITION SENSOR (NE-SIGNAL) n POWERTRAIN CONTROL MODULE ENGINE COOLANT TEMPERATURE SENSOR I (ENGINE) 1 DETERMINA- TION OF FUEL CUT SPEED Gartner Banana

COOLANT FAN CONTROL COOLANT FAN CONTROL OUTLINE The PCME controls the coolant fan and the condenser fan to provide more efficient fan control. This 4 improves the performance reliability and stability during idling of an engine. The coolant fan is normal when it start to operate with the data link connector TEN terminal grounded and the accerelator pedal is depressed (Ignition switch ON). IGNITION SWITCH OFF CONDENSER FAN MOTOR PCME RELAY I& MAGNETIC CLUTCH I COOLANT FAN RELAY Q COOLANT FAN MOTOR Gartner Banana