Lack of Power, Sluggishness, or Sponginess. GMC Truck GMC Suburban

For 1990-2009 cars only

Makes 🢒 GMC_Truck 🢒 1998 🢒 GMC Suburban - 2WD 🢒 Engine 🢒 Engine Controls - 7.4L 🢒 Lack of Power, Sluggishness, or Sponginess

Checks

Action

Definition: The engine delivers less than expected power. There is little or no increase in speed when partially applying the accelerator pedal.

Preliminary Checks

•	Refer to Symptoms .

•	Compare the customer's vehicle with a similar unit. Verify the customer concern.

•	Remove the air filter and check for dirt or a restriction.

•	Check the transmission shift pattern and the downshift operation. Refer to Functional Test in Automatic Transmission.

Fuel System Checks

•	Check for a restricted fuel filter, contaminated fuel, or improper fuel pressure. Refer to Fuel System Diagnosis .

•	Perform the fuel injector balance test. Refer to Fuel Injector Balance Test .

Exhaust System Checks

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

•	Inspect the exhaust system for damaged or collapsed pipes. Inspect the muffler for heat distress or a possible internal failure.

Additional Checks

•	Check the Control Module grounds for being clean, tight, and in their proper location.

•	Check the EGR Valve for being open or partially open all the time. Refer to Exhaust Gas Recirculation (EGR) System Diagnosis .

•	Check the Torque Converter Clutch (TCC) operation. Refer to Functional Test in Automatic Transmission.

•	Check the A/C operation. Refer to Air Conditioning (A/C) Compressor Control Circuit Diagnosis .

•	Check the generator output voltage. Refer to Charging System Check in Engine Electrical.

•	Check the Knock Sensor (KS) system.

Engine Mechanical Check

Check the engine for the proper operation of the following items:

•	Engine compression

•	Valve timing

•	Improper or worn camshaft.