Cuts Out/Misses

DEFINITION
Steady pulsation or jerking that follows engine speed, usually more pronounced as engine load increases. This condition is not normally felt above 1500 RPM or 48 km/h (30 mph). The exhaust has a steady spitting sound at idle or low speed.

PRELIMINARY STEPS

^ Before starting, refer to Important Preliminary Checks Testing and Inspection
and
Visual and Physical Checks. - Visual/Physical Underhood Inspection

^ Search for Technical Service Bulletins.

^ Check PCM grounds for being clean, tight and in their proper locations. Refer to Diagrams / Electrical / Engine Controls for PCM ground numbers and locations. Electrical Diagrams

^ Remove and check air filter element for dirt, or for being restricted.

FUEL SYSTEM

^ Perform injector balance test. Refer to Fuel Injector Balance Test. Fuel Injector Balance Test

^ Check for low fuel pressure. Refer to Fuel System Diagnosis. System Diagnosis - Fuel System

^ Check for restricted fuel filter.

^ Check for contaminated fuel. Refer to Alcohol/Contaminants-In-Fuel Test.

^ Check items which can cause an engine to run rich (long term fuel trim near -14%). For a Rich condition, refer to DTCs:

P0132 HO2S Circuit High Voltage Bank 1 Sensor 1 P0132
OR
P0152 HO2S Circuit High Voltage Bank 2 Sensor 1. P0152

^ Check items that can cause an engine to run lean (long term fuel trim near 22%). For a Lean condition, refer to DTCs:

P0131 HO2S Circuit Low Voltage Bank 1 Sensor 1 P0131
OR
P0151 HO2S Circuit Low \ Voltage Bank 2 Sensor 1. P0151

SENSOR/SYSTEM

Using a scan tool, monitor Knock Sensor (KS) system for excessive spark retard activity.

IGNITION SYSTEM

^ Wetting down the secondary ignition system with water from a spray bottle may help locale damaged or deteriorated components. Look/listen for arcing or misfiring as water is applied.

^ Check for proper ignition voltage output with spark tester J 26792.

^ Remove spark plugs and check for the following:

- Wet plugs

- Cracks

- Wear

- Improper gap

- Burned electrodes

- Heavy deposits

^ An improper spark plug gap will cause a driveability problem. Refer to Spark Plug / Specifications for correct gap. Specifications

^ The spark plug gapping should be done using a wire gauge gap tool (J 41319). Refer to Spark Plug Replacement. Service and Repair

^ If spark plugs are gas or oil fouled, the cause of the fouling must be determined before replacing the spark plugs. To determine the rich condition, refer to DTCs:

P0172 Fuel Trim System Rich Bank 1 P0172
OR
P0175 Fuel Trim System Rich Bank 2. P0175

For the oil fouling condition, refer to Engine. Engine

^ Visually/Physically inspect Secondary ignition for the following:

- Ignition wires for cross firing.

- Ignition wires arcing to ground.

- Ignition wires for proper routing.

- Distributor cap for cracks or carbon tracking.

^ Wetting down the secondary ignition system with water from a spray bottle may help locate damaged or deteriorated components. Look/listen for arcing or misfiring as water is applied.

^ Check for loose ignition coil ground. Refer to Distributor Ignition System Check. System Check - Distributor Ignition (DI)

^ Spark plugs for proper heat range.

^ Check distributor vent system for being restricted or open. Refer to Distributor Vent System Check. System Check - Distributor Vent

ENGINE MECHANICAL

^ Check engine mechanical for the following:

- Check compression.

- Sticking or leaking valves.

- Worn camshaft lobe(s).

- Valve timing.

- Bent push rods.

- Worn rocker arms.

- Broken valve springs.

- Excessive oil in combustion chamber-Leaking valve seals.

- Low cylinder compression.

^ For incorrect basic engine pans. Inspect the following:

- Camshaft

- Cylinder heads

- Pistons, etc.

ADDITIONAL CHECKS

^ Check exhaust system for possible restrictions. Check for the following:

- Inspect exhaust system for damaged or collapsed pipes.

- Inspect mufflers for heat distress or possible internal failure.

- For possible plugged Three-Way catalytic converters by comparing exhaust system back pressure on each side of engine. Check back pressure by removing Secondary Air Injection (AIR) check valves near exhaust manifolds. Refer to Restricted Exhaust System Check under this heading. System Check - Restricted Exhaust

^ An engine miss condition can be caused by Electromagnetic Interference (EMI) on the reference circuit. EMI can usually be detected by monitoring engine RPM with a scan tool. A sudden increase in RPM with little change in actual engine RPM change, indicates EMI is present. If a problem exists, check routing of secondary ignition wires, high voltage components (Near Ignition Control circuits). Check distributor ground circuit for being open or loose.

^ Check for intake and exhaust manifold passages for casting flash. Refer to:

Engine / Intake Manifold Intake Manifold
OR
Exhaust System / Exhaust Manifold. Exhaust Manifold