Checks
| Action
|
DEFINITION: A steady pulsation or jerking that follows
the engine speed. The condition is usually more pronounced as the engine
load increases.
|
Preliminary
|
| • | Refer to Important Preliminary Checks Before Starting. |
| • | Refer to Visual/Physical Checks |
|
Fuel System
|
| • | Test the fuel injectors using the following tests: |
| • | Inspect for conditions which can cause an engine to run rich,
indicating a long-term fuel trim that is significantly in the negative range.
Refer to
DTC P0172 Fuel Trim System Rich
. |
| • | Inspect for conditions that can cause an engine to run lean, indicating
that the long-term fuel trim is significantly in the positive range. Refer
to
DTC P0171 Fuel Trim System Lean
. |
| • | Inspect for fuel in the fuel pressure regulator vacuum hose. |
|
Sensor/System
|
- Inspect for conditions which can cause an incorrect idle speed.
| - | Inspect for a large vacuum leak. |
- Test the TP Sensor and test the related circuit wiring. Refer
to
DTC P0123 Throttle Position (TP) Sensor Circuit High Voltage
.
- Test the EGR system for proper operation. Refer to
Exhaust Gas Recirculation (EGR) System Description
.
- Test the PCV for proper operation. Refer to
Crankcase Ventilation System Description
.
- Test the transaxle range switch input with the vehicle in drive,
and with the gear selector in drive or overdrive.
- Inspect for the following components:
| - | Bent harmonic balancer interrupter rings for bends |
| - | A damaged crankshaft position sensor |
|
Ignition System
|
| • | Check for proper ignition voltage output using the following steps: |
| 1. | Clip the spark tester J 26792
to engine ground. |
| 2. | Connect one end of a spark plug wire to the spark tester, and
leave the other end of the spark plug wire to the coil that is being tested. |
| 3. | Connect one end of another spark plug wire to the other coil tower,
and connect the other end of the spark plug wire to ground. |
| 4. | Crank the engine while you observe the spark tester. You should
observe a spark. |
| 5. | Repeat the above steps for each coil. |
| • | If there is no spark at the coils, inspect for the following conditions: |
| - | The coils--Inspect for cracks, for carbon tracking or arcing,
or for a secondary resistance value that is outside the specified range. |
Coil Resistance
5000-8000 ohms (5K-8K ohms) | - | The spark plug wires--Inspect for signs of arcing or cross-firing,
for cracks, for carbon tracking, for plug boot damage, for pinches, for improper
routing, or a resistance value that is outside the specified range. |
Spark Plug Wire Resistance
600 ohms per ft.
| | Important: Spraying the secondary ignition wires with a light mist of water may
help to locate an intermittent problem. Ignition components will arc to ground
when a secondary component is faulty.
|
| - | The ignition System Wiring--Inspect for a loose ignition
module feed or ground connection, or for damaged system wiring. |
| • | Remove the spark plugs and inspect for the following conditions: |
| - | Burned or damaged electrodes |
| - | Improper heat range or reach |
| • | If the spark plugs are gas or oil fouled, determine the cause
of the fouling before you replace the spark plugs. |
| • | Test for the following intermittent ignition system conditions: |
| - | An intermittent CKP 18X signal. |
| - | An intermittent ignition feed circuit or sensor ground circuit
to the crankshaft position sensor or to the camshaft position sensor |
| - | An intermittent 3X reference signal |
| - | An intermittent camshaft position signal |
|
Engine Mechanical
|
| • | Test and inspect the engine mechanical components for the following
conditions: |
| - | Sticking or leaking valves |
| - | Excessive oil in the combustion chamber that is caused by leaking
valve seals. |
| - | Low cylinder compression |
| • | Inspect for incorrect basic engine parts. Inspect the following
conditions: |
| - | Other components, as applicable |
|
Additional Checks
|
| • | Test the exhaust system for possible restrictions. Inspect for
the following conditions: |
| - | Damaged or collapsed pipes in the exhaust system. |
| - | Heat distress or possible internal failure in the muffler |
| • | An engine miss condition can be caused by electromagnetic interference
(EMI) on the reference circuit. You can usually detect EMI by monitoring
the engine RPM with a scan tool. A sudden increase in RPM, with little
change in the actual engine RPM indicates that EMI is present. If a
problem exists, inspect the routing for the secondary ignition wires, and
for high voltage components that are near the ignition control circuits. |
| • | Inspect for faulty motor mounts. |
|
