EGR System Ford Tempo I

INTRODUCTION

Note. Introduction information not applicable.

DESCRIPTION

The Exhaust Gas Recirculation (EGR) system distributes small amounts of exhaust gas into the intake mixture. This lowers combustion temperatures due to lower concentrations of oxygen. Lowering of combustion temperatures reduces amount of NOx emissions. The amount of exhaust gas recycled and timing of EGR valve opening are controlled by engine vacuum, exhaust system backpressure, altitude, temperature, throttle angle and engine speed.

Typical systems consist of an EGR valve, vacuum reservoir, check valve, Ported Vacuum Switch (PVS) and/or a Temperature Vacuum Switch (TVS). The following 5 types of EGR valves are used

1. Backpressure Variable Transducer (BVT)
2. Electronic (EEGR)
3. Integral Backpressure (IBP) transducer
4. Ported
5. Pressure Feedback Electronic (PFE)

The valve and transducer assembly consists of a modified ported EGR valve and a remote transducer. This assembly works the same as the integral backpressure transducer EGR valve and is diagnosed and serviced as an assembly only. Valve functional checks are the same as those for the integral backpressure transducer EGR valve. see scheme 1

Electronic (EEGR) EGR Valve

This valve is operated by a vacuum signal from one of the dual EGR solenoid valves or the electronic vacuum regulator. As vacuum overcomes closing spring pressure, the diaphragm is actuated, lifting pintle off its seat and causing exhaust gas to flow. Flow is proportional to pintle position. The EVP sensor on the valve sends an electrical signal relevant to valve position to the Electronic Control Assembly (ECA). (Scheme 86)

The electronic EGR valve assembly is not serviceable. The EVP sensor and EGR valve are serviced separately. The EVP sensor mounted on top of the valve sends out electrical signals to the Electronic Control Assembly (ECA) which indicate how far the EGR valve is open.

The ECA then signals the EGR control solenoids to maintain or alter the control vacuum supply to the EGR valve as required. Vacuum is obtained from the intake manifold and is bled off or applied to the EGR diaphragm by the ECA. A cooler is sometimes used to reduce gas temperatures and detonation. This valve operates only during partial throttle mode. It is closed in all other modes.

Electronic EGR Valve. Scheme 86

Integral Backpressure (IBP) Transducer EGR Valve

This EGR valve combines inputs of exhaust backpressure and EGR port vacuum into one unit. Both inputs are required for the valve to operate. There are 2 types of exhaust backpressure valves: poppet and tapered pintle. The integral backpressure transducer valve combines an exhaust gas backpressure transducer within its diaphragm housing. The transducer controls EGR function by venting control vacuum in relation to exhaust backpressure.

In order for the valve to operate, sufficient exhaust backpressure is required to close a bleed valve located inside the vacuum diaphragm housing. Until this bleed valve closes, all vacuum routed to the valve has no effect. When the bleed valve closes, vacuum is applied to the diaphragm. The valve opens allowing exhaust gas to flow. Flow rate is dependent on source vacuum, exhaust pressure, control setting and orifice size.

Poppet valves are rapid opening. Flow rate is limited by size of valve orifice or opening in carburetor spacer plate.

Internal tapered stem valves use a pintle which moves the tapered portion of the valve up or down against its valve seat. Flow rate is determined by the amount of movement off the seat.

Integral Backpressure Transducer EGR Valve. Scheme 87

Ported EGR Valve

This valve is operated by a vacuum signal from the carburetor EGR port which actuates the EGR valve diaphragm. When vacuum is increased enough to overcome the diaphragm closing spring pressure, the valve opens, allowing EGR flow. Amount of flow is dependent on pintle or poppet position which is a direct result of the strength of the vacuum signal and valve type.

Ported EGR Valve. Scheme 88

Pressure Feedback Electronic (PFE) EGR Valve

This valve consists of a conventional ported EGR valve which has a tube attached to it to sense backpressure. A pressure transducer is used with this valve to send an electrical signal to the ECA, corresponding to the amount of backpressure. The EGR flow is proportional to the amount of pressure drop across the sense tube.

Pressure Feedback Electronic (PFE) EGR Valve System used with EEC equipped vehicles only. Scheme 89

Backpressure Variable Transducer (BVT)

This remotely mounted regulator modulates the vacuum signal to the EGR valve. It is one of the components in the BVT EGR valve system. It uses 2 backpressure inputs to control vacuum supply to the EGR valve. One input is from the EGR valve control chamber, the other is downstream from the flow control orifice.

EGR Load Control (WOT) Valve

This valve dumps EGR vacuum at or near wide open throttle. This valve senses venturi vacuum at a predetermined level and causes the EGR valve to close. When engine load is then reduced from wide open throttle, the EGR load control valve closes and completes the vacuum pathway to the EGR.

EGR Solenoid Vacuum Valve Assembly

This assembly consists of 2 solenoid valves, one to supply vacuum to the EGR valve when energized, the other vents EGR vacuum source to the atmosphere when de-energized. Solenoids are controlled by the ECA. The vacuum supply line has a restrictor in its inlet port to reduce its flow compared to the vent solenoid, which is unrestricted.

EGR Vacuum Control Valve Filter

This component is a small in-line filter that is inserted into the vent lines to protect the various system components which have a vent line open to the atmosphere.

EGR Valve Position Sensor (EVP)

The EVP is attached to the top of the EGR valve. It measures the amount the EGR valve opens and sends a corresponding signal to the ECA. The ECA uses this signal to adjust EGR opening signal. The EVP sensor is removable from the EGR valve and is serviced separately.

EGR Venturi Vacuum Amplifier

Because venturi vacuum is not sufficient to operate EGR valve diaphragm, a vacuum amplifier is used. This amplifier steps up the signal of venturi vacuum to a level that can control the EGR valve. This amplifier also contains a check and relief valve that opens whenever vacuum signal is equal to or greater than manifold vacuum.

Pressure Feedback Electronic EGR Transducer

Converts exhaust pressure to a proportional analog electrical signal which is sent to the ECA. The ECA uses this signal to regulate EGR flow and control exhaust emissions.

Temperature Vacuum Switch (TVS)

Temperature vacuum switch is used to delay EGR operation to provide better cold engine driveability. Switch contains a normally open bi-metallic disc which allows free airflow in vacuum line. When closed, it blocks airflow by sealing against an "O" ring.

The dual EGR solenoid valve assembly consists of one vacuum valve that supplies vacuum to the EGR valve when it is energized and a vent valve that vents EGR vacuum to the atmosphere when de-energized. Both valves receive signals from the ECU. A restrictor is added in the vacuum valve inlet port so the vent valve may vent if the vacuum valve sticks open.

Scheme 90

1. Ensure vacuum system is correctly routed and in serviceable condition. Start and ensure there is no vacuum to EGR valve at idle (engine at normal operating temperature). Install a tachometer.
2. Disconnect ISC connector (MPFI and SEFI engines). Disconnect and plug vacuum supply hose from EGR valve nipple. Ensure engine idle speed is within specification. (Scheme 90): Backpressure Variable Transducer (BVT)
3. Using a hand pump, slowly apply 5-10 in. Hg vacuum to EGR valve. With vacuum applied, idle speed should drop about 100 RPM (engine may stall). If speed does not drop, replace EGR valve. If speed drops, release vacuum and ensure engine speed returns to normal +/-25 RPM.
4. Reconnect ISC connector and EGR supply hose. Disconnect vacuum connection at BVT. (Scheme 90) Lightly blow into the hose to port "A" until relief valve closes and at the same time apply 5-10 in. Hg of vacuum to port "C", using a hand vacuum pump. Port "C" should hold vacuum as long as there is pressure to port "B".
5. Apply 5-10 in. Hg vacuum to ports "A" and "B". These ports should hold vacuum. Replace transducer if any ports do not hold vacuum. Reconnect vacuum hoses to BVT ports.

1. Ensure vacuum system is correctly routed and in serviceable condition. Start engine and ensure there is no vacuum to EGR valve at idle (engine at normal operating temperature). Install a tachometer. NOTE: The EVR control solenoid has a small constant vent leak. The vacuum signal to the EGR valve should be less than 2.5 in. Hg at idle.
2. Disconnect ISC (Air By-pass Valve) connector (MPFI and SEFI engines). Disconnect and plug vacuum supply hose from EGR valve nipple. Ensure engine idle speed is within specification. Using a hand pump, slowly apply 5-10 in. Hg vacuum to EGR valve nipple.
3. Apply vacuum to the EGR valve. Replace EGR valve if any of the following conditions exist: Engine does not stall. Idle speed does not drop 100 RPM (minimum). Idle speed does not return to normal when vacuum is removed.
4. Reconnect the ISC connector. Reconnect EGR valve vacuum supply.

1. Ensure vacuum system is correctly routed and in serviceable condition. There should be no vacuum to EGR valve at idle (engine at normal operating temperature). Disconnect ISC solenoid connector. Install a tachometer.
2. Plug the exhaust tailpipe(s) to increase exhaust backpressure for testing purposes. Leave a 1/2" hole to allow exhaust gases to escape. Disconnect and plug vacuum supply hose from EGR valve nipple. Start engine and ensure engine idle speed is within specification.
3. Using a hand pump, slowly apply 5-10 in. Hg vacuum to EGR valve. With vacuum applied, idle speed should drop about 100 RPM (engine may stall). If speed does not drop, replace EGR valve. If speed drops, release vacuum and ensure engine speed returns to normal +/-25 RPM.
4. Reconnect ISC connector and EGR supply hose. Remove plugs from exhaust tailpipe.

1. Ensure vacuum system is correctly routed and in serviceable condition. There should be no vacuum to EGR valve at idle (engine at normal operating temperature). Disconnect ISC connector. Install a tachometer.
2. Disconnect and plug vacuum supply hose from EGR valve nipple. Start engine and ensure engine idle speed is within specification. Using a hand pump, slowly apply 5-10 in. Hg vacuum to EGR valve. With vacuum applied, idle speed should drop about 100 RPM (engine may stall).
3. If speed does not drop, replace EGR valve. If speed drops, release vacuum and ensure engine speed returns to normal +/-25 RPM. Reconnect ISC connector and EGR supply hose.

1. Ensure vacuum system is correctly routed and in serviceable condition. There should be no vacuum to EGR valve at idle (engine at normal operating temperature). Disconnect ISC connector. Install a tachometer.
2. Disconnect and plug vacuum supply hose from EGR valve nipple. Start engine and ensure engine idle speed is within specification. Using a hand pump, slowly apply 5-10 in. Hg vacuum to EGR valve. With vacuum applied, idle speed should drop about 100 RPM (engine may stall).
3. If speed does not drop, replace EGR valve. If speed drops, release vacuum and ensure engine speed returns to normal +/-25 RPM. Reconnect ISC connector and EGR supply hose.

1. This valve dumps EGR vacuum to the atmosphere at or near full throttle. With engine running at normal temperature, set throttle on kickdown step (high cam). Connect vacuum gauge to EGR side of WOT valve.
2. Apply a minimum of 6 in. Hg vacuum to WOT valve port "C". (Scheme 91) Gauge should drop to zero. If not, replace valve. Adjust WOT valve so vacuum applied by hand pump will drop when near WOT.

EGR Load Control (WOT) Valve. Scheme 91

1. The resistance of each solenoid should be 32-64 ohms. Replace any solenoid which is not in this resistance range. The vent valve should allow flow when the solenoid is de-energized.
2. The control valve should allow flow when the solenoid is energized. The valves may have a very small leakage rate during testing.

Solenoid Flow Diagram. Scheme 92

EGR Valve Position Sensor (EVP)

Note. For EVP sensor testing procedures, see appropriate article in the COMPUTERIZED ENGINE CONTROLS section.

Venturi Vacuum Amplifier

1. Check for adequate manifold vacuum. With engine warm and at curb idle, connect vacuum gauge to port "O" on amplifier which leads to EGR/PVS valve. Vacuum should not read more than 2 in. Hg at idle.
2. Disconnect venturi hose at carburetor. Increase engine speed to 2000 RPM. Vacuum should not change. Maintain high engine speed and reconnect venturi hose.
3. Gauge should register at least 4 in. Hg vacuum. Return engine to idle. Gauge should return to initial reading. If not, replace amplifier.

Venturi Vacuum Amplifier. Scheme 93

Pressure Feedback Electronic (PFE) EGR Transducer

Note. For PFE EGR transducer testing procedure, see appropriate article in the COMPUTERIZED ENGINE CONTROLS section.

Using a vacuum pump, apply 16 in. Hg of vacuum to the motor side of the switch. Ensure vacuum switch meets specifications. See VACUUM SWITCH SPECIFICATIONS table.

VACUUM SWITCH SPECIFICATIONS (1)

With the solenoid disconnected, check the resistance between the solenoid terminals. Resistance should be 51-108 ohms. Replace solenoid if not to specification. Ports should allow flow of air when solenoid is energized. Operational signal for solenoid is supplied by the ECA.

ENGINE STALLS ON DECELERATION (HOT OR COLD)

EGR valve stuck open, or not closing fully. BVT malfunction. EGR mounting flange gasket leaking or loose. VCV or TVS malfunction. Blocked or restricted EGR flow ports. WOT valve malfunction. Vacuum leak at EVP sensor. Idle speed too high. Ignition timing retarded.

ROUGH IDLE (HOT OR COLD)

EGR valve receiving vacuum from misrouted hoses. EGR valve not closing fully or stuck open, blown gasket or attachment loose, air bleeds plugged (backpressure valves). TVS or PVS opening too early when engine cold. EFI computer malfunction. Vacuum regulator leaking (BVT system). WOT valve malfunction. Curb idle set too high.

POOR PART THROTTLE PERFORMANCE (RUNS ROUGH, SURGES, HESITATES)

EGR valve stuck closed. BVT system malfunction. Leaky valve diaphragm or flange gasket. Vacuum restricted to EGR valve or EGR disconnected. TVS and/or PVS not opening, load control (WOT) valve venting or EGR passages blocked. Insufficient backpressure (exhaust leaks) to operate EGR system. EVP sensor "O" ring leaking or sensor loose (EEC). Ignition timing retarded.

SPARK KNOCK OR PING

EGR valve leaking at mounting or internally. VCV or TVS malfunction. Plugged or restricted passage ways or ports. Exhaust leaks provide insufficient backpressure to activate valve. Ignition timing too far advanced.

ENGINE STALLS AT IDLE (COLD)

EGR valve leaking at mounting or internally. PVS or TVS malfunction. Ignition timing retarded. BVT system malfunction. Idle speed too high. Vacuum leak at EVP sensor. WOT valve malfunction.

ENGINE STALLS AT IDLE (HOT)

EGR valve leaking at mounting or internally. PVS or TVS malfunction. Ignition timing retarded. Idle speed too high. Vacuum leak at EVP sensor. WOT valve malfunction. Blocked or restricted passageways

VERY LOW POWER AT FULL THROTTLE

Load control (WOT) valve not venting or EGR valve stuck open. EGR mounting gasket leaking. Vacuum leak at EVP sensor. BVT system malfunction. Ignition timing retarded. Blocked or restricted passageways

POOR FUEL ECONOMY

Note. If EGR related, poor fuel economy is usually accompanied by detonation or other symptom of restricted or no EGR flow.

EGR valve leaking at mounting or internally. PVS or TVS malfunction. Ignition timing retarded. BVT system malfunction. Vacuum leak at EVP sensor. WOT valve malfunction. Blocked EGR passages or ports. Insufficient exhaust backpressure to operate EGR valve.