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