EGR System - Piston Eng Mazda MX-6 V

DESCRIPTION

Note. For information on 929 EGR system, refer to COMPUTERIZED ENGINE CONTROLS section.

The Exhaust Gas Recirculation (EGR) system allows measured amounts of exhaust gas into the intake manifold to reduce oxides of nitrogen (NOx).

The EGR system on B2200 models consists of EGR control valve, EGR valve position sensor, duty solenoid valve, vacuum check valves and connecting hoses and pipes.

The EGR system on B2600 models consists of EGR control valve, EGR modulator valve, EGR solenoid valves and EGR vacuum switches.

The EGR system on MX-6 and 626 models consists of EGR control valve, EGR modulator valve (non-turbo), EGR solenoid valve (non-turbo), EGR position sensor (turbo), duty solenoid valve (turbo), vacuum check valve, and connecting hoses and pipes.

OPERATION

Under various engine speed and operating conditions, regulated vacuum to the EGR control valve allows measured amounts of exhaust gas into the intake manifold. This reduces the air/fuel combustion temperature and reduces the amount of oxides of nitrogen (NOx) in the exhaust gas.

Scheme 12

Scheme 13

Scheme 14

Scheme 15

B2200

Bring engine to normal operating temperature and stop engine. Disconnect and plug vacuum hose at EGR control valve. Connect vacuum pump to EGR control valve. Start engine and run at idle. Apply 1.97 in. Hg or more to EGR control valve with vacuum pump. Engine should run rough or stop. If procedure fails, test EGR position sensor. If position sensor tests good, clean or replace EGR control valve.

B2600

1. Bring engine to normal operating temperature and stop engine. Disconnect and plug vacuum hose at EGR control valve. Connect vacuum pump to 1st EGR control valve. Start engine and run at idle. Apply 1.58 in. Hg or more to EGR control valve with vacuum pump. Engine should run rough or stop.
2. Repeat procedure on 2nd EGR control valve, applying 2.76 in. Hg or more. Engine should run rough or stop.

MX-6 & 626

Bring engine to normal operating temperature and run at idle. Disconnect and plug vacuum hose at EGR control valve. Engine should run smoothly. Connect vacuum pump to EGR control valve and apply more than 2.36 in. Hg. Engine should run rough or stop. If procedure fails, clean or replace EGR control valve.

Bring engine to normal operating temperature and run at idle. Disconnect EGR position sensor connector. Using an ohmmeter, ensure the resistance is within the specifications. (Scheme 16) See TERMINAL RESISTANCE SPECIFICATION table. If resistance is not within specifications, replace EGR position sensor.

Scheme 16

Scheme 17

1. With engine off and ignition switch in the "ON" position, disconnect vacuum hose at EGR control valve and connect a vacuum pump. Using a voltmeter, test EGR position sensor terminal connector. (Scheme 17) See «TERMINAL VOLTAGE SPECIFICATION»(/mazda/mx-6/v-1986-1991/remont/testing-diagnostics/#egr-system-piston-eng) table.
2. If A and B do not meet specifications, check wiring harness and EGI control unit. If C does not meet specifications, check resistance of EGR position sensor, wiring harness and EGI control unit.
3. Disconnect EGR position sensor connector. Using an ohmmeter, test resistance of connector. (Scheme 17) See «TERMINAL RESISTANCE SPECIFICATION»(/mazda/mx-6/v-1986-1991/remont/testing-diagnostics/#egr-system-piston-eng) table. Replace EGR position sensor if not within specification.

Remove EGR modulator valve. Plug No. 1 port and connect vacuum pump to No. 3 port. Blow into exhaust gas port. Operate vacuum pump and ensure that vacuum is held. Release exhaust gas port and check that vacuum is released.

MX-6 & 626 Non-Turbo

Remove EGR modulator valve. Connect vacuum pump to No. 1 port and plug No. 2 and No. 3 ports. (Scheme 18) Apply vacuum and blow into exhaust gas port. Ensure vacuum holds. Release exhaust gas port and ensure vacuum is released. Replace EGR modulator valve if defective.

Scheme 18

Remove vacuum hose from EGR control valve and vent hose at intake manifold. Blow through vent hose and ensure air passes through valve. Disconnect duty solenoid valve connector. Apply battery power to terminal "B" and ground terminal "C". (Scheme 19) Blow through vent hose and ensure air does not pass through valve. Replace duty solenoid valve if defective.

Scheme 19

MX-6 & 626 Turbo

Remove vacuum valve hose at vacuum chamber. Remove vent valve hose at air cleaner. Remove vacuum hose at EGR control valve. Blow through vent valve hose and ensure air passes. Disconnect duty solenoid valve connector. Apply battery power to terminal "D" and ground terminal "C". (Scheme 20) Blow through vacuum hose and ensure air passes through valve. Replace duty solenoid valve if defective.

Scheme 20

Remove vacuum hose and vent hose. Blow through vacuum hose and ensure air does not pass through valve. Disconnect duty solenoid valve connector. Apply battery power to terminal "D" and ground terminal "A". (Scheme 19) Blow through vacuum hose and ensure air passes through valve. Replace duty solenoid valve if defective.

Remove vacuum valve hose at vacuum chamber. Remove vent valve hose at air cleaner. Remove vacuum hose at EGR control valve. Blow through vacuum hose and ensure air does not pass through valve. Disconnect duty solenoid valve connector. Apply battery power to terminal "B" and ground terminal "A". (Scheme 20) Blow through vacuum hose and ensure air passes through valve. Replace duty solenoid valve if defective.

Remove vacuum hoses and electrical connector. Remove EGR solenoid valve. (Scheme 21) Blow air through port "A" and ensure air passes out port "B". Apply battery power and ground to connector. Blow air through port "A" and ensure air passes out air filter. Replace EGR solenoid valve if defective.

Scheme 21

B2200, MX-6 & 626

Remove vacuum check valve. By blowing through vacuum check valve, ensure vacuum travels through in the direction of the arrow marked on the valve. Reverse airflow through vacuum check valve and ensure air does not flow. Replace vacuum check valve if defective.

Start engine and run at idle. Before engine reaches normal operating temperature, increase engine speed to 2000 RPM and verify EGR control valve diaphragm does not move. Bring engine to normal operating temperature and run at idle. Increase engine speed to 2000 RPM and verify EGR control valve diaphragm does move.

Scheme 22

1. Warm engine to normal operating temperature and let idle. Disconnect vacuum hose "A" from 1st EGR control valve and check that engine runs smoothly. If not, replace 1st EGR control valve. (Scheme 22)
2. Connect vacuum gauge to vacuum hose "A". Increase engine speed to 2500 RPM and check that gauge reads more than 5.9 in. Hg. If not correct, check coolant thermovalve, coolant temperature switch, No. 1 EGR solenoid valve and No. 2 EGR vacuum switch (M/T only). Reconnect vacuum hose "A" to 1st EGR control valve.
3. Disconnect vacuum hose "B" from 2nd EGR control valve and check that engine runs smoothly. If not, replace 2nd EGR control valve. (Scheme 22)
4. Connect vacuum gauge to vacuum hose "B". Increase engine speed to 2500 RPM and check that gauge reads more than 5.9 in. Hg. If not correct, check No. 2 EGR solenoid valve and No. 1 EGR vacuum switch.
5. Disconnect vacuum hose "C" from EGR modulator valve and plug it. Connect test hose "D" to port of EGR modulator valve. Increase engine speed to 2500 RPM. Blow into test hose "D" and check that vacuum increases. If not correct, check EGR modulator valve. Reconnect vacuum hose "C" to EGR modulator valve. (Scheme 23)

Scheme 23

Scheme 24

1. Check all connectors, hoses and routings for cracks, leakage, or restrictions and repair as needed. Bring engine to normal operating temperature and run at idle. Remove and plug vacuum hose at EGR control valve. If engine runs rough, test EGR control valve.
2. Remove plug from vacuum hose at EGR control valve and connect vacuum gauge. Remove and plug vacuum hose at bottom of EGR modulator valve and connect a suitable hose in its place. (Scheme 24) Increase engine speed to 2000 RPM and blow into hose. If no increase of vacuum is noted, test EGR modulator valve. Reinstall hoses to EGR modulator valve and EGR control valve.
3. Remove vacuum hose from EGR modulator valve marked No. 1 and connect vacuum gauge. Increase engine speed to 2500 RPM. Vacuum should be more than 5.9 in. Hg. Test EGR solenoid valve if vacuum is less. With vacuum gauge still installed, disconnect Green/Black wire of coolant temperature switch. Increase engine speed to 2500 RPM and ensure no vacuum is present. If vacuum is present, test EGR solenoid valve and EGI control unit at "2N" terminal.

1. Check all connectors, hoses and routings for cracks, leakage, or restrictions and repair as needed. Bring engine to normal operating temperature and run at idle. Remove and plug vacuum hose at EGR control valve. If engine runs rough, test EGR control valve.
2. Remove plug from vacuum hose and connect vacuum gauge. With engine at idle, vacuum should not be present. Increase engine speed to 2500 RPM. Vacuum should be present. If procedure fails, test duty solenoid valve and EGI control unit terminals "2M" and "2N".
3. Install vacuum gauge between duty solenoid valve and EGR control valve. Increase engine speed to 2000 RPM and note amount of vacuum. Disconnect and plug vacuum hose at EGR control valve. Increase engine speed to 2000 RPM. Vacuum should be greater than previous reading. If procedure fails, test EGR position sensor, EGR duty solenoid valve and EGI control unit terminal "2F".
4. With vacuum hose disconnected at EGR control valve and vacuum gauge connected, disconnect Green/Black wire of coolant temperature switch. Increase engine speed to 2500 RPM and ensure vacuum is not present. If vacuum is present, test duty solenoid valve and EGI control unit terminal "1H".

TERMINAL RESISTANCE

TERMINAL RESISTANCE SPECIFICATION

TERMINAL VOLTAGE

TERMINAL VOLTAGE SPECIFICATION

See also:
• TERMINAL RESISTANCE SPECIFICATION