Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
1998 Oldsmobile Aurora V8-4.0L VIN CFACTORY OEM SERVICE PROCEDURE
Exhaust Gas Recirculation: Testing and Inspection
EGR DIAGNOSIS
Too much EGR flow tends to weaken combustion, causing the engine to run roughly or stop. With too much EGR flow at idle, cruise, or cold operation, any of the following conditions may occur:
^ Engine stops after cold start.
^ Vehicle surge.
^ Engine stops at idle after deceleration or idles rough.
If the EGR valve is stuck open, the engine may not run.
Low or no EGR flow allows combustion temperatures to get too high during acceleration and load conditions. This could cause:
^ Spark knock (detonation), especially on light acceleration.
^ Emission test failure.
This powertrain system runs several tests on the EGR system and a fault in the EGR circuits, the flow of the EGR valve or the controllability of the valve should set a PCM DTC.
Too much EGR flow tends to weaken combustion, causing the engine to run roughly or stop. With too much EGR flow at idle, cruise, or cold operation, any of the following conditions may occur:
^ Engine stops after cold start.
^ Vehicle surge.
^ Engine stops at idle after deceleration or idles rough.
If the EGR valve is stuck open, the engine may not run.
Low or no EGR flow allows combustion temperatures to get too high during acceleration and load conditions. This could cause:
^ Spark knock (detonation), especially on light acceleration.
^ Emission test failure.
This powertrain system runs several tests on the EGR system and a fault in the EGR circuits, the flow of the EGR valve or the controllability of the valve should set a PCM DTC.
Factory Service Tools
Use the Manual With the Right Hardware
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.
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