DEFINITION: A steady pulsation or jerking that follows engine speed, usually more pronounced as the engine load increases. The exhaust has a steady spitting sound at idle, low speed, or on hard acceleration.

Preliminary Checks

Ignition System Checks

Important: Do not perform this test for more than 2 minutes in order to prevent damage to the catalytic converter.

Check for ignition misfire.

1. Start the engine.
2. Disconnect the fuel injectors one at the time.
3. An equal RPM drop on all cylinders (within 50 RPM) indicates a common condition that is affecting all cylinders.
4. Check for spark on the suspected cylinders with a J 26792 spark tester, or equivalent, if there is no RPM drop on one or more cylinders.
5. If there is no spark, Refer to Engine Cranks but Does Not Run .
6. If there is spark, check the spark plugs for any of the following conditions:

-	Wet (fuel fouled) spark plugs

-	A terminal screw that is bent or loose (rotate and pull)

-	A ceramic insulator that has cracks, carbon tracking, or deposits (red or black dust)

-	A tip insulator that has cracks, carbon tracking, deposits (oil, carbon, glazing, fuel additive), or is loose (rattles)

-	A center electrode that is loose (wiggles side to side)

-	An incorrect spark plug gap that is too large or too small

-	Platinum pads that are missing

Engine Mechanical Checks

Fuel System Checks