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

Check for an ignition system misfire:

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

1. Start the engine.
2. Remove one spark plug wire at a time, using insulated pliers.
3. If there is a RPM drop on all cylinders (equal to within 50 RPM), Refer to Rough, Unstable, or Incorrect Idle and Stalling .
4. Check for spark on the suspected cylinder(s) with a spark tester (J 26792 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) 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.

7. Check the spark plug wire resistance (should not exceed 30,000 ohms).
8. Check the distributor cap and the distributor rotor.
9. Check the ignition system for moisture, dust, cracks, burns, etc.
10. Run the engine and spray the secondary ignition system with water in order to check for shorts.

Engine Mechanical Checks

Fuel System Checks