Cuts Out, Misses. GMC Truck TopKick C-Series (Conventional) C4/C5 2005

For 1990-2009 cars only

Makes 🢒 GMC_Truck 🢒 2005 🢒 TopKick C-Series (Conventional) C4/C5 🢒 Engine 🢒 Engine Controls - 8.1L 🢒 Cuts Out, Misses

Inspections

Action

DEFINITION: Steady pulsation or jerking that follows engine speed, usually more pronounced as engine load increases. This condition is not normally felt above 1,500 RPM or 48 km/h (30 mph). The exhaust has a steady spitting sound a idle or low speed.

Preliminary

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

•	Search for bulletins.

•	Inspect the powertrain control module (PCM) grounds for being clean, tight, and in the proper locations. Refer to Power and Grounding Component Views in Wiring Systems and Engine Controls Schematics .

•	Remove the air filter element and inspect for dirt or for being restricted. Refer to Air Cleaner Element Replacement . Replace as necessary.

Fuel System

•	Test the fuel injectors. Refer to Fuel Injector Solenoid Coil Test .

•	Test for incorrect fuel pressure. Refer to Fuel System Diagnosis .

•	Test for a contaminated fuel condition. 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.

-	Water intrusion 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--Refer to Fuel System Diagnosis .

-	Rich fuel injectors--Refer to Fuel System Diagnosis .

-	Inaccurate mass air flow (MAF) sensor--Refer to Scan Tool Data List .

-	Blockage on the inlet screen of the MAF sensor--Refer to Mass Airflow Sensor/Intake Air Temperature Sensor Replacement .

-	Vacuum hoses for splits, kinks and proper connections

-	The air intake duct for being collapsed or restricted--Refer to Air Cleaner Outlet Front Duct Replacement .

-	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.

-	Water intrusion in the HO2S connector

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

-	Vacuum leaks

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

-	Lean fuel injectors--Refer to Fuel System Diagnosis .

-	An inaccurate MAF sensor--Refer to Scan Tool Data List .

-	Fuel contamination--Refer to Alcohol/Contaminants-in-Fuel Diagnosis .

-	Vacuum hoses for splits, kinks and proper connections

Sensor/System

Monitor the knock sensor for excessive spark retard with a scan tool.

Ignition System

•	Wet down the secondary ignition system with water from a spray bottle. Wetting down the secondary ignition system may help locate damaged or deteriorated components. Look and listen for arcing or misfiring as you apply water.

•	Test for proper ignition voltage output with J 26792 spark tester .

•	Remove the spark plugs and inspect for the following conditions. Refer to Spark Plug Inspection :

-	Correct heat range

Wet plugs

Cracks

Wear

-	Improper gap

-	Burned electrodes

-	Heavy deposits

•	An improper spark plug gap will cause a driveability problem. Gap the spark plugs using a wire gage gap tool. Refer to Spark Plug Replacement .

•	Determine the cause of the fouling before replacing the spark plugs if the spark plugs are gas, coolant, or oil fouled. Refer to Spark Plug Inspection for diagnosis of fouled spark plugs.

•	Monitor the Misfire Current Counters while driving the vehicle in the conditions that the misfire occurred. If a cylinder can be located with a misfire, refer to Electronic Ignition (EI) System Diagnosis for diagnosis.

•	Inspect for loose ignition coil grounds. Refer to Electronic Ignition (EI) System Diagnosis .

•	Visually and physically inspect the secondary ignition for the following:

-	Spark plug wires arcing to ground

-	Spark plug wires for proper engagement to spark plug

-	Ignition coils for cracks or carbon tracking

Engine Mechanical

•	Inspect engine mechanical for the following:

-	Test compression--Refer to Engine Compression Test in Engine Mechanical .

-	Sticking or leaking valves

-	Worn camshaft lobes

-	Valve timing

-	Bent push rods

-	Worn rocker arms

-	Broken valve springs

-	Excessive oil in combustion chamber--Leaking valve seals. Refer to Oil Consumption Diagnosis in Engine Mechanical .

•	Inspect the following components for incorrect basic engine parts. Refer to the appropriate procedures in Engine Mechanical for diagnosis procedures:

Camshaft

-	Cylinder heads

-	Pistons, etc.

•	Inspect for excessive crankshaft endplay that will cause the CKP sensor reluctor wheel to move out of alignment with the CKP sensor. Refer to Crankshaft and Bearing Cleaning and Inspection in Engine Mechanical. This could result in any of the following conditions:

-	A no start

-	A start and stall

-	Erratic performance

Additional

•	Inspect the following components of the exhaust system for possible restrictions:

-	The exhaust system for damaged or collapsed pipes

-	The exhaust manifold for a collapsed inner wall

-	The mufflers for heat distress or possible internal failure

-	Compare the exhaust system back pressure on each side of engine. Refer to Restricted Exhaust in Engine Exhaust.

•

Electromagnetic interference (EMI) on the reference circuit can cause an engine miss condition. A sudden increase in the engine speed parameter on the scan tool indicated RPM with little change in actual engine RPM change indicates EMI is present. Inspect for high voltage components near ignition control circuits if a problem exists.

•	Inspect the intake manifold and the exhaust manifold passages for casting flash.