EGR valve
EGR valve refers to the exhaust gas recirculation valve used by the Pontiac Fiero EGR system.
The EGR valve controls the flow of exhaust gas into the intake system. It is part of the emissions-control system and is controlled indirectly by the ECM through the EGR solenoid and vacuum system.
Overview
EGR stands for Exhaust Gas Recirculation.
The EGR valve allows a controlled amount of exhaust gas to enter the intake under certain operating conditions. This helps reduce combustion temperature and emissions.
The EGR valve is not supposed to be open all the time. If it opens at the wrong time, stays open, leaks, or does not open when needed, it can cause drivability problems or emissions problems.
Location
Image wanted: Photo or diagram showing the EGR valve location on the Fiero. Ideally include the 2.8L V6 EGR valve, EGR tube connection, and vacuum line connection. A 2.5L four-cylinder example would also be useful.
The EGR valve location depends on engine and year.
On the 2.8L V6, the EGR valve is mounted near the intake manifold area and is connected to the exhaust system through the EGR tube. A vacuum line from the EGR solenoid controls valve operation.
On the 2.5L four-cylinder, the EGR valve is also mounted where it can route exhaust gas into the intake, though the exact layout and appearance may vary by year.
The EGR valve should not be confused with the EGR solenoid. The solenoid controls vacuum; the valve controls exhaust-gas flow.
Function
When operating conditions are correct, the ECM allows vacuum to reach the EGR valve through the EGR solenoid.
Vacuum opens the EGR valve. When the valve opens, exhaust gas flows into the intake stream.
The EGR valve is normally closed during conditions where EGR would hurt drivability, such as idle, cold start, and wide-open throttle.
Related trouble codes
EGR-valve-related diagnostic trouble codes include:
- Code 32 - EGR system
Code 32
Code 32 indicates that the ECM has detected a problem with EGR vacuum control or EGR system operation.
Possible EGR-valve-related causes include:
- Faulty EGR valve
- EGR valve stuck closed
- EGR valve stuck open
- EGR valve unable to hold vacuum
- Restricted EGR passages
- Leaking EGR valve
- EGR tube leak
- Vacuum control problem
- EGR solenoid problem
Symptoms
Possible symptoms of an EGR valve problem include:
- Check engine light
- Code 32
- Rough idle
- Stalling
- Hesitation
- Poor drivability
- Spark knock or pinging
- Failed emissions test
- Vacuum leak symptoms
- Little or no obvious drivability problem
Stuck-open EGR valve
An EGR valve that is stuck open or leaking at idle can cause rough idle, stalling, or poor low-speed operation.
At idle, the engine generally should not receive EGR flow. If exhaust gas enters the intake at the wrong time, combustion quality can suffer.
Related topics:
Stuck-closed EGR valve
An EGR valve that does not open when commanded may cause emissions problems or spark knock under certain driving conditions.
A stuck-closed valve may not always cause obvious drivability symptoms.
Vacuum operation
The Fiero EGR valve is vacuum-operated. The valve should respond to vacuum when tested according to the correct service procedure.
Possible vacuum-related problems include:
- No vacuum reaching the valve
- Leaking vacuum line
- Incorrect vacuum-line routing
- Defective EGR solenoid
- EGR valve diaphragm unable to hold vacuum
Related topics:
EGR tube
On the 2.8L V6, the EGR tube connects the EGR system to the intake. A cracked EGR tube can act like a vacuum leak and may cause high idle, lean running, hesitation, or other drivability problems.
Related topics:
Diagnosis
Basic diagnostic checks include:
- Check for stored diagnostic trouble codes.
- Inspect the EGR valve and surrounding area.
- Inspect the vacuum line to the EGR valve.
- Check whether the EGR valve can hold vacuum if applicable.
- Check whether the valve opens when vacuum is applied.
- Inspect the EGR solenoid and vacuum-control system.
- Inspect the EGR tube for cracks or leaks.
- Check for vacuum leaks.
- Check for restricted or clogged EGR passages if EGR flow is suspected to be blocked.
- Check ECM control and wiring if the valve, solenoid, tube, and vacuum system appear correct.
Notes
Code 32 should not automatically be treated as a failed EGR valve.
Vacuum lines, the EGR solenoid, wiring, connectors, the EGR tube, vacuum supply, and ECM control should also be checked.
An EGR valve problem can affect drivability, but some EGR faults may cause only a check engine light or emissions-test failure.