For 1990-2009 cars

Checks | Action
--- | ---
DEFINITION: Steady pulsation or jerking that follows engine speed, usually more pronounced as engine load increases.
Preliminary |

• | Refer to the Powertrain On Board Diagnostic (OBD) System Check .

• | Refer to Intermittent Conditions in Wiring Systems.

• | Search for bulletins.

Fuel System |

• | Check system fuel pressure. Refer to Fuel System Pressure Test .

• | Check the fuel injectors. Refer to Fuel Injector Balance Test , Fuel Injector Solenoid Coil Test - Engine Coolant Temperature Between 10-35 Degrees C (50-95 Degrees F) , or Fuel Injector Solenoid Coil Test - Engine Coolant Temperature Outside 10-35 Degrees C (50-95 Degrees F) .

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

• | Check items which can cause an engine to run rich (long term fuel trim significantly in the negative range). Refer to Diagnostic Aids for DTC P0172.

• | Check items that can cause an engine to run lean (long term fuel trim significantly in the positive range). Refer to Diagnostic Aids for DTC P0171.

• | Check for fuel in the Fuel Pressure Regulator vacuum hose.

Sensor/System |

• | Check for conditions which cause an incorrect idle speed.

- | Throttle body tampering, excessive deposits, or damage. Refer to Fuel Supply Component Description .

- | Restricted air intake system.

- | Large vacuum leak.

• | Check the TP Sensor and related circuit wiring. Refer to DTC P0123 Diagnosis.

• | Check the EGR system for proper operation. Refer to EGR System Description .

• | Check the PCV Valve for proper operation. Refer to Crankcase Ventilation System Description .

• | Check the Transaxle Range Switch input with the vehicle in drive and the gear selector in drive or overdrive.

• | Check the following for damage:

• | Bent harmonic balancer interrupter rings.

• | Damaged Crankshaft Position Sensor.

Ignition System |

• | Check for proper ignition voltage output using the following steps:

- | Clip the J 26792 Spark Tester to engine ground.

- | Connect one end of a spark plug wire to the J 26792 Spark Tester, leave the other end of the spark plug wire to the coil being tested.

- | Connect one end of another spark plug wire to the other coil tower; connect the other end of the spark plug wire to ground.

- | Crank the engine while observing the J 26792 Spark Tester; a spark should be observed.

- | Repeat the above steps for each coil.

• | If adequate spark is not present at the coil(s), check for the following conditions:

- | Coil(s)--Cracks, carbon tracking/arcing, or a resistance value outside the specified range.

Coil Resistance
5000-8000ohms (5K-8Kohms)

- | Spark Plug wires--Signs of arcing/cross firing, cracks, carbon tracking, plug boot damage, pinched, improper routing, or a resistance value outside the specified range.

Spark Plug Wire Resistance
600ohms per foot (1 968ohms per meter).

| Important: : Spraying the secondary ignition wires with a light mist of water may help locate an intermittent problem. Ignition components will arc to ground when a secondary component is faulty.

- | Defective module.

- | Ignition System Wiring--Loose ignition module feed or ground connection, or damaged system wiring.

• | Remove spark plugs and check for the following:

- | Fouled plugs

- | Cracks

- | Wear

- | Improper gap

- | Burned or damaged electrodes

- | Improper heat range or reach

• | If spark plugs are gas or oil fouled, the cause of the fouling must be determined before replacing the spark plugs.

• | Check for the following intermittent ignition system conditions:

- | Intermittent CKP 24X Signal.

- | Intermittent ignition feed circuit or sensor ground circuit to the crankshaft position sensor or the camshaft position sensor.

- | Intermittent 3X reference signal.

- | Intermittent camshaft position signal

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. Refer to Oil Consumption Diagnosis in Engine Mechanical.

- | Low cylinder compression. Refer to Engine Compression Test in Engine Mechanical.

• | For incorrect basic engine parts. 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 converter. Refer to Restricted Exhaust , and Restricted Exhaust System Check .

• | 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 for intake and exhaust manifold passages for casting flash. Refer to Engine Mechanical.

• | Check for faulty motor mounts. Refer to Engine Mechanical.