For 1990-2009 cars

Checks | 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 at idle or low speed.
Preliminary |

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

• | Search for bulletins.

• | Check the powertrain control module (PCM) grounds for being clean, tight, and in the proper locations. Refer to Engine Controls Schematics .

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

Fuel System |

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

• | Check for incorrect fuel pressure. Refer to Fuel System Diagnosis .

• | Check for a restricted fuel filter. Refer to Fuel System Diagnosis .

• | Check for a contaminated fuel condition. Refer to Alcohol/Contaminants-in-Fuel Diagnosis .

• | Check items that cause an engine to run rich long term fuel trim near -13 percent. For a rich condition, refer to DTC P0132 or P0152 .

• | Check items that can cause an engine to run lean, long term fuel trim near 24 percent. For a lean condition, refer to DTC P0131 or P0151 .

Sensor/System | Use a scan tool in order to monitor the knock sensor system for excessive spark retard activity.
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.

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

• | Remove the spark plugs and check 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.

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

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

- | Ignition wires arcing to ground

- | Ignition wires for proper engagement to spark plug

- | Ignition coils for cracks or carbon tracking

Engine Mechanical |

• | Check engine mechanical for the following:

- | Check compression--Refer to Engine Compression Test in Engine Mechanical - 8.1L.

- | 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 - 8.1L.

• | 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.

Additional Checks |

• | 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

- | The three-way catalytic converters for possible plugged conditions--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 indicated RPM with little change in actual engine RPM change indicates EMI is present. Check for high voltage components near ignition control circuits if a problem exists.

• | Check the intake manifold and the exhaust manifold passages for casting flash.