Checks
| Action
|
DEFINITION: A jerking
that follows the engine speed, and is usually more pronounced when the engine
load increases. The condition is not normally felt above 1,500 RPM,
or 48 km/h (30 mph).
|
Preliminary Check
| Refer to
Symptoms - Engine Controls
.
|
Ignition System Checks
| Check for a cylinder misfire:
- Start the engine.
- Allow the engine to stabilize.
- Disconnect the idle air control (IAC) motor.
Notice: Do not perform this test for more than 2 minutes in order to
prevent damaging the catalytic converter.
- Perform the Cylinder Power Balance Test with a scan tool.
- If there is a RPM drop on all cylinders, equal to within 50 RPM,
refer to
Rough, Unstable, or Incorrect Idle and Stalling
.
- Reconnect the IAC motor with the ignition OFF.
- If there is no RPM drop on one or more of the cylinders, or if
excessive variation in drop occurs, check for spark on the suspected cylinders
with a J 26792
Spark Tester
or equivalent.
- If there is no spark, refer to
Distributor Ignition (DI) System Diagnosis
.
- If there is spark, remove the spark plugs in these cylinders and
check for the following conditions:
- Check the spark plug wire resistance. The resistance should not
exceed 30,000 ohms.
- Check the distributor rotor and the distributor cap.
- If the previous check did not find the problem, visually check
the following items:
- Check the ignition system for the following items:
- With the engine running, spray the plug wires with a fine water
mist in order to check for shorts.
- Perform the Fuel Injector Balance Test. Refer to
Fuel Injector Balance Test with Tech 2
.
|
Engine
Mechanical Checks
|
• | Perform a cylinder compression check. |
• | Check the engine for the following conditions: |
• | Check the intake and exhaust manifold passages for casting flash. |
|
Fuel
System Checks
|
• | Check for water contamination in the fuel. |
|
Additional
Check
|
• | Check for electromagnetic interference (EMI). |
• | Check the routing of the secondary wires and the ground circuit. |
|