Hesitation, Sag, Stumble. Cadillac DeVille 2005

For 1990-2009 cars only

Makes 🢒 Cadillac 🢒 2005 🢒 DeVille 🢒 Engine 🢒 Engine Controls - 4.6L 🢒 Hesitation, Sag, Stumble

Inspection/Test

Action

DEFINITION: Momentary lack of response as the accelerator is pushed down. Can occur at any vehicle speed. Usually more pronounced when first trying to make the vehicle move, as from a stop sign. May cause the engine to stall if severe enough.

Preliminary

•	Refer to Important Preliminary Check Before Starting in Symptoms - Engine Controls .

•	Search for bulletins.

Sensor/System

•

Inspect the heated oxygen sensors (HO2S)s for proper operation. The sensors should respond quickly to different throttle positions. If not, inspect the sensors for silicon from RTV sealant, or other contaminants from the fuel. The sensors may have a white powdery coating. Silicon contamination causes a false high signal voltage (rich exhaust indicated). The powertrain control module (PCM) will reduce the amount of fuel delivered to the engine.

•	Test the manifold absolute pressure (MAP) sensor for proper operation. Refer to DTC P0106.

•	Test the throttle body, throttle position (TP) sensor, and accelerator cables for proper operation. Refer to DTC P0121.

•	Test the exhaust gas recirculation (EGR) system for proper operation. Refer to Exhaust Gas Recirculation (EGR) System Description .

Fuel System

•	Test the fuel pressure. Refer to Fuel System Diagnosis .

•	Test the fuel injectors. Refer to the following:

-	Fuel Injector Balance Test with Tech 2 or Fuel Injector Balance Test with Special Tool .

-	Fuel Injector Solenoid Coil Test .

•	Test for fuel contamination. Refer to Alcohol/Contaminants-in-Fuel Diagnosis .

Inspect the following that may cause the engine to run rich:

Notice: Refer to Heated Oxygen and Oxygen Sensor Notice in the Preface section.

•	Any water intrusion in the HO2S connector

•	Engine oil contaminated by fuel

•	An evaporative emission (EVAP) canister purge condition

•	Incorrect fuel pressure--Refer to Fuel System Diagnosis .

•	A leaking fuel pressure regulator

•	Any rich fuel injectors--Refer to Fuel Injector Balance Test with Tech 2 and Fuel Injector Balance Test with Special Tool .

•	Inaccurate mass air flow (MAF) sensor

•	Blockage on the inlet screen of the MAF sensor

•	Vacuum hoses for splits, kinks and proper connections

•	The air intake duct for being collapsed or restricted

•	The air filter for being dirty or restricted--Refer to Air Cleaner Element Replacement .

Inspect the following that may cause the engine to run lean:

Notice: Refer to Heated Oxygen and Oxygen Sensor Notice in the Preface section.

•	Any water intrusion into the HO2S connector

•	An exhaust leak between the HO2S and the engine--Refer to Exhaust Leakage in Engine Exhaust.

•	Any vacuum leaks

•	Incorrect fuel pressure--Refer to Fuel System Diagnosis .

•	Any lean fuel injectors--Refer to Fuel Injector Balance Test with Tech 2 and Fuel Injector Balance Test with Special Tool .

•	An inaccurate MAF sensor

•	Fuel Contamination--Refer to Alcohol/Contaminants-in-Fuel Diagnosis .

•	Vacuum hoses for splits, kinks and proper connections

Ignition System

•	Inspect the ignition control (IC) circuits for proper connections at each ignition module assembly.

•	Test for proper ignition voltage output using the J 26792 Spark Tester.

•	Inspect the ignition coils for cracks or damage.

•	Inspect for a missing or damage ignition module assembly grounding spring.

•	Inspect for misaligned or damaged spark plug boots.

•	Inspect the spark plugs. Refer to Spark Plug Inspection .

Additional

Inspect the vacuum hoses for splits, kinks, damage, improper connections, or routing.