Cuts Out, Misses
Checks
| Action
|
DEFINITION: A steady pulsation or jerking that follows the engine speed.
When the engine load increases, the condition is usually more pronounced.
|
Preliminary
|
| • | Search for service bulletins. |
|
Fuel
System
|
| • | Inspect the fuel filter for being plugged or restricted. |
| • | Inspect the items which can cause an engine to run rich, with
a long term fuel trim significantly in the negative range. Refer to Diagnostic
Aids for
DTC P0172
. |
| • | Inspect the items that can cause an engine to run lean, with a
long term fuel trim significantly in the positive range. Refer to Diagnostic
Aids for
DTC P0171
. |
| • | Ensure proper operation of the evaporative emission (EVAP) control
system. |
| • | Inspect for fuel in the fuel pressure regulator vacuum hose. |
|
Sensor/System
|
| • | Inspect the oxygen sensor (O2S 1). The O2S 1 should
respond quickly to different throttle positions. If not, inspect the O2S 1
for silicon or for other contaminants from the fuel, or from the use of improper
room-temperature vulcanizing (RTV) sealant. The sensors may have
a white powdery coating. Silicon contamination causes a high but
false O2S 1 signal voltage, indicating a rich exhaust condition.
The powertrain control module (PCM) will reduce the amount of
fuel that is delivered to the engine, causing a severe driveability
problem. |
| • | Ensure proper operation of the manifold absolute pressure (MAP)
sensor. |
| • | Ensure proper operation of the throttle position (TP) sensor. |
| • | Ensure proper operation of the engine coolant temperature (ECT)
sensor. |
|
Ignition
System
|
| • | Ensure proper ignition voltage output with the J 26792
Spark Tester or equivalent. |
| • | Inspect the spark plugs for the following conditions: |
| - | Wet or fuel fouled spark plugs |
| - | Cracks on the spark plugs |
| - | Improper spark plug gap |
| - | Burned electrodes or heavy deposits |
| • | If the spark plugs are fuel or oil fouled, the cause of the fouling
must be determined before replacing the spark plugs. |
| • | Inspect the ignition control module (ICM) for proper ground connection. |
| • | Inspect the ignition coils for cracks or carbon tracking. |
| • | Inspect the spark plug wires for proper resistance and condition. |
|
Engine
Mechanical
|
| • | Inspect for the following conditions: |
| - | Sticking or leaking valves |
| - | Excessive oil in combustion chamber due to leaking valve seals |
| - | Low cylinder compression |
| • | Inspect for incorrect basic engine parts. Inspect the following: |
| - | Other basic engine parts, as appropriate |
|
Additional
Checks
|
| • | Inspect the exhaust system for possible restrictions. Inspect
for the following conditions: |
| - | For damaged or collapsed pipes |
| - | The mufflers for heat distress or for possible internal failure |
| - | For a possible plugged three-way catalytic converter (TWC)--Refer
to
Restricted Exhaust
in Engine Exhaust. |
| • | An engine miss condition can be caused by electromagnetic interference
(EMI) on the reference circuit. EMI can usually be detected by monitoring
engine revolution per minute (RPM) with a scan tool. A sudden
increase in RPM with little change in actual engine RPM change,
indicates EMI is present. If a condition exists, inspect the
routing of the secondary ignition wires, and inspect for high voltage
components near the ignition control (IC) circuits. |
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