Exhaust Gas Recirculation: Testing and Inspection

RESULTS OF INCORRECT OPERATION
Too much Exhaust Gas Recirculation (EGR) flow dilutes the fresh intake air/fuel mixture, causing the engine to run roughly or stall. With too much EGR flow (at idle, cruise, or cold operation) tends to weaken combustion and may result in any of the following conditions:

- Engine stops after cold start.
- Engine stops at idle after deceleration.
- Vehicle surges during cruise.
- Rough idle.

Too little or no EGR flow allows combustion temperatures to get too high during acceleration and load conditions. This could cause:

- Spark knock (detonation).
- Engine overheating.
- Emission test failure.

SCAN TOOL DIAGNOSIS
Diagnosis of the Exhaust Gas Recirculation (EGR) system is covered in Computers and Controls / System Diagnosis / Procedures / Diagnostic Chart C-7 Exhaust Gas Recirculation (EGR) System Check, if DTC 27 or 32 was not set. Testing and Inspection