Exhaust Gas Recirculation: Testing and Inspection

EGR FAILURE MODES
Too Much EGR Flow
If too much EGR is flowing at idle, cruise, or cold operation, any of the following conditions could exist:

a. The engine dies after cold start.
b. The engine stalls on deceleration.
c. The vehicle surges during cruise mode.
d. Rough idle.

Too Little EGR Flow
If too little or no exhaust gases flow, the combustion chamber temperature may increase under acceleration or heavy load conditions. These conditions could cause:

a. Detonation (Spark Knock).
b. The engine to overheat.
c. The emissions test to fail.

ADDITIONAL INFORMATION
For diagnostic procedures, refer to Computers and Control Systems/System Diagnosis/Procedures/Diagnostic Charts/Chart C-7 Exhaust Gas Recirculation Check. Chart C-7 EGR System Check