Checks
| Action
|
Definition: A steady
or jerking that follows engine speed, usually more pronounced as the engine
load increases which is not normally felt above 1500 RPM or 48 km/h
(30 mph).. The exhaust has a steady spitting sound at idle, low speed,
or hard acceleration for the fuel starvation that can cause the engine to
cut-out.
|
Preliminary Check
| Refer to
Important Preliminary Checks
.
|
Ignition System Checks
| Check for a cylinder misfire:
- Start the engine.
- Allow the engine to stabilize.
- Then 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.
- Remove one spark plug wire at a time using insulated pliers.
- If there is a RPM drop on all cylinders (equal to within 50 RPM),
go 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 excessive
variation in drop, check for spark on the suspected cylinders with a J 26792
or the equivalent.
- If there is no spark, refer to
Enhanced Ignition System
.
- If there is spark, remove the spark plugs in these cylinders and
check for the following conditions:
- | Check the spark plug wire 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: |
• | The ignition system for moisture, dust, cracks, burns, etc. |
• | With the engine running, spray the plug wires with a fine water
mist to check for shorts. |
|
Engine Mechanical Checks
|
• | Perform a cylinder compression check. Refer to Engine Mechanical. |
• | Check the engine for the following: |
- | Broken or weak valve springs Refer to Engine Mechanical. |
• | Check the intake and exhaust manifold passages for casting flash.
Refer to Engine Mechanical. |
|
Fuel System Checks
|
• | Check for water contamination in the fuel. |
• | Check the fuel injector driver circuit. |
|
Additional Check
| Check for Electromagnetic
Interference (EMI).
• | EMI on the reference circuit can cause a missing condition. |
• | Monitoring the engine RPM with a scan tool can detect an EMI. |
• | A sudden increase in the RPM with little change in the actual
engine RPM, indicates EMI is present. |
• | If the problem exists, check the routing of the secondary wires
and the ground circuit. |
|