Definition: A steady pulsation or jerking that follows the engine speed. This symptom is usually more pronounced as the engine load increases, but is not normally felt above 1500 RPM or 48 km/h (30 mph). The exhaust has a steady spitting sound at idle, at low speed or on hard acceleration for fuel starvation that can cause the engine to cut out.

Did you perform the Powertrain On-Board Diagnostic (OBD) System Check?

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Go to Step 2

Go to Powertrain On Board Diagnostic (OBD) System Check

Perform the careful visual/physical checks as described at the start of the Symptoms section.

Did you perform the visual/physical check?

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Go to Step 3

Go to Important Preliminary Checks

Is DTC P0300, P0301, P0302, P0303, or P0304 set?

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Go to applicable DTC table

Go to Step 4

1. Check the spark plugs for the following conditions:

•	Insulator cracks

•	An improper gap

•	Burned electrodes

•	Heavy deposits

2. If any of the above conditions are present, replace the spark plugs.

Did any of the plugs require replacement?

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Go to Step 13

Go to Step 5

1. Disconnect all of the injector harness connectors and install an injector test light J 34730-2 between the harness terminal connector of each injector.
2. Crank the engine and observe the light on each connector. If the test light fails to blink at any one of the connectors, this could be the result of a malfunctioning injector drive circuit harness, connector, or terminal.

Did the test light blink on all of the injector harness connectors?

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Go to Step 6

Go to applicable misfire DTC table

1. Check the fuel pressure. Perform the procedure in the Fuel System Diagnosis .
2. If a problem is present, repair the problem as necessary.

Was a repair necessary?

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Go to Step 13

Go to Step 7

1. Check for contaminated fuel.
2. If a problem is present, repair the problem as necessary.

Was a repair necessary?

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Go to Step 13

Go to Step 8

1. Perform the Fuel Injector Solenoid Coil Test or Fuel Injector Balance Test .
2. Replace any malfunctioning injector.

Were any injector(s) replaced?

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Go to Step 13

Go to Step 9

1. Check the engine mechanical for the following conditions. Refer to Engine Mechanical for the diagnosis procedures.

•	A low compression

•	Sticking or leaking valves

•	Worn camshaft lobe(s)

•	Incorrect valve timing

2. If a problem is present, repair the problem as necessary.

Was a repair necessary?

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Go to Step 13

Go to Step 10

1. Check the Intake and exhaust manifold(s) for casting flash. Refer to Engine Mechanical section .
2. If a problem is present, repair the problem as necessary.

Was a repair necessary?

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Go to Step 13

Go to Step 11

1. Check for Electromagnetic Interference (EMI). A missing condition can be caused by EMI on the reference circuit. You can usually detect an EMI by monitoring the engine RPM with a scan tool. A sudden increase in the RPM with little change in the actual engine RPM change indicates that an EMI is present.
2. If an EMI is present, locate and repair the source.

Was a repair necessary?

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Go to Step 13

Go to Step 12

1. Review all of the diagnostic procedures within this table.
2. If all of the procedures have been completed and no malfunctions are present, visually/physically inspect the following items:

•	The scan tool data

•	All of the electrical connections within a suspected circuit and/or system

3. If a problem is present, repair the problem as necessary.

Was a repair necessary?

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Go to Step 13

Check for Service Bulletins

Operate the vehicle within the conditions under which the original symptom was observed.

Does the system now operate properly?

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System OK

Go to Step 2