Surges/Chuggles. GMC Truck Envoy

For 1990-2009 cars only

Makes 🢒 GMC_Truck 🢒 2007 🢒 Envoy - 2WD 🢒 Diagnostic Navigation 🢒 Vehicle Diagnostic Information 🢒 Surges/Chuggles

Inspections

Action

DEFINITION: The engine has a power variation under a steady throttle or cruise. The vehicle feels as if it speeds up and slows down with no change in the accelerator pedal position.

Preliminary Inspections

•	Refer to Symptoms - Engine Controls .

•	Be sure that the driver understands the torque converter clutch operation.

•	Be sure that the driver understands the A/C compressor operation.

•	Ensure that the transmission fluid is at the proper level.

Sensor/System

Display the scan tool parameters for the various engine controls sensors. Inspect for any abnormal readings.

Fuel System

•	Inspect for a rich or lean symptom that causes the condition. Drive the vehicle at the speed of the complaint. Monitoring the fuel trim will help identify the condition.

-	Lean--The long term fuel trim will be more than 150.

-	Rich--The long term fuel trim will be less than 115.

•	Test the fuel pressure while the condition exists. Refer to Fuel System Diagnosis .

•	Inspect the in-line fuel filter for a restrictions.

Ignition System

Inspect the spark plugs. Remove the plugs and inspect for the following conditions:

•

Wetness

•

Cracks

•

Wear

•	Improper gap

•	Burned electrodes

•	Heavy deposits

Refer to Spark Plug Inspection .

Additional

•	Inspect the control module grounds for being clean, tight, and in their proper locations. Refer to Power and Grounding Component Views .

•	Test the generator output voltage. Refer to Diagnostic System Check - Vehicle .

•	Inspect the vacuum hoses for kinks or leaks.

•	Inspect the torque converter clutch (TCC) operation. Refer to Torque Converter Diagnosis .

•	Inspect the exhaust system for a possible restriction. Refer to Restricted Exhaust .