Results of Incorrect Operation

Too much EGR flow tends to weaken combustion, causing the engine to run roughly or to stop. With too much EGR flow at idle, cruise or cold operation, any of the following conditions may occur:

• The engine stops after a cold start.
• The engine stops at idle after deceleration.
• The vehicle surges during cruise.
• Rough idle

If the EGR valve stays open all the time, the engine may not idle. Too little or no EGR flow allows combustion temperatures to get too high during acceleration and load conditions. This could cause the following conditions:

• Spark knock (detonation)
• Engine overheating
• Emission test failure