Checks
| Action
|
DEFINITION: Steady pulsation or jerking that follows
engine speed, usually more pronounced as engine load increases.
|
Preliminary
|
• | Search for service bulletins. |
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Fuel System
|
• | Test the fuel filter for being plugged or restricted. |
• | Inspect 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
. |
• | Inspect items that can cause an engine to run lean (Long Term
FT significantly in the positive range). Refer to Diagnostic Aids for
DTC P0171 Fuel Trim System Lean
. |
• | Test for proper operation of the evaporative emission (EVAP)
control system. |
• | Inspect for fuel in the fuel pressure regulator vacuum hose. |
|
Sensor/System
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• | The O2S 1 should respond quickly to different throttle
positions. If not, inspect 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
Information Sensors/Switches Description
. |
• | Test for proper operation of the following sensors: |
|
Ignition System
|
• | Test for proper ignition voltage output with a J 26792
Spark Tester or equivalent. |
• | Inspect the spark plugs for the following conditions: |
- | Burnt 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. |
• | Test the ignition coils for cracks or carbon tracking. |
• | Test/inspect the spark plug wires for proper resistance and condition. |
|
Engine Mechanical
| Inspect the engine for the following engine mechanical
problems:
• | Check engine mechanical for the following conditions: |
• | For incorrect basic engine parts. Inspect the following: |
|
Additional Checks
|
• | Inspect the exhaust system for the following conditions: |
- | Damaged or collapsed pipes |
- | Mufflers for heat distress or possible internal failure |
• | 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, inspect routing of secondary ignition
wires, high voltage components (near ignition control circuits). |
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