Checks
| Action
|
DEFINITION: Steady
pulsation or jerking that follows engine speed, usually more pronounced as
engine load increases.
|
Preliminary
|
• | Search for service bulletins. |
• | Connect a scan tool and look at the misfire data to possibly isolate
a specific cylinder fault. |
|
Fuel System
|
• | Inspect the fuel filter for a plugged or restricted condition. |
• | Inspect items which can cause an engine to run rich--Short
term FT is significantly in the negative range. Refer to Diagnostic Aids for
DTC P0172
. |
• | Inspect items that can cause an engine to run lean--Short
term FT significantly in the positive range. Refer to Diagnostic Aids for
DTC P0171
. |
• | Inspect for proper operation of the evaporative emission (EVAP)
control system. |
|
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 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 powertrain control module (PCM) will reduce
the amount of fuel delivered to the engine, causing a severe driveability
problem. |
• | Inspect for proper operation of the manifold absolute pressure
(MAP) sensor. |
• | Inspect for proper operation of the throttle position (TP) sensor. |
• | Inspect for proper operation of the engine coolant temperature
(ECT) sensor. |
• | Inspect for proper operation of the crankshaft position (CKP)
sensor. |
• | Inspect for proper operation of the camshaft position (CMP) sensor. |
|
Ignition System
|
• | Inspect for proper ignition voltage output with a J 26792
Spark Tester or equivalent. |
• | Using a scan tool, monitor cylinder misfire to pinpoint a specific
cylinder. |
• | 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 engine mechanical for the following: |
- | Sticking or leaking valves |
- | Excessive oil in combustion chamber and leaking valve seals |
- | Low cylinder compression |
• | Inspect the following components for incorrect basic engine parts: |
|
Additional Checks
|
• | Inspect the following components of the exhaust system for possible
restrictions: |
- | Inspect exhaust system for damaged or collapsed pipes. |
- | Inspect mufflers for heat distress or possible internal failure. |
• | An engine miss condition can be caused by electromagnetic interference
(EMI) on the CKP reference circuit. EMI can usually be detected by monitoring
medium resolution counter with a scan tool. A reading other than zero indicates
EMI is present. If a problem exists, inspect routing of secondary
ignition wires high voltage components--Near ignition control
circuits. |
• | Inspect for malfunctioning motor mounts. |
|