Checks
| Action
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DEFINITION: Steady
pulsation or jerking that follows engine speed, usually more pronounced as
engine load increases.
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Preliminary
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• | Refer to Important Preliminary Checks Before Starting in
Symptoms
. |
• | Refer to Visual/Physical checks in
Symptoms
. |
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Fuel System
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• | Check system fuel pressure. |
• | Check the fuel injectors. |
• | 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
. |
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Sensor/System
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• | Check for conditions which cause an incorrect idle speed. |
- | Throttle body tampering, excessive deposits, or damage. |
- | Check for a large vacuum leak. |
- | Inspect the EGR pipes and adapter for vacuum leaks. |
• | Check the Transaxle Range Switch input with the vehicle in drive
and the gear selector in drive or overdrive. Refer to Transaxle Range Switch
Valid Combinations table in
DTC P0705 Trans Range Switch Circuit
. |
• | Check for the following conditions: |
- | Check for a bent harmonic balancer interrupter rings. |
- | Check for a damaged Crankshaft Position Sensor. |
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Ignition System
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• | Check for proper ignition voltage output using the following steps: |
- | Clip the spark tester J 26792 to engine ground. |
- | Connect one end of a spark plug wire to the spark tester; leave
the other end of the spark plug wire to the coil being tested. |
- | Connect one end of another spark plug wire to the other coil tower;
connect the other end of the spark plug wire to ground. |
- | Crank the engine while observing the spark tester; a spark should
be observed. |
- | Repeat the above steps for each coil. |
• | If spark is not present at the coil(s), check for the following
conditions: |
- | Inspect the coil(s) for cracks, carbon tracking/arcing, or a secondary
resistance value outside the specified range. |
Coil Secondary Resistance 5000 - 8000 ohms (5K - 8K ohms) - | Inspect the spark plug wires for signs of arcing/cross firing,
cracks, carbon tracking, plug boot damage, pinched, incorrect routing, or
a resistance value greater than the specified value. |
VIN 1 Spark Plug Wires Resistance 3280 - 4921 ohms per meter (1000 ohms - 1500 ohms per foot)
VIN K Spark Plug Wires Resistance 3280 - 4921 ohms per meter (1000 ohms - 1500 ohms per foot)
| Important: Spraying the secondary ignition wires with a light mist of water may
help locate an intermittent problem. Ignition components will arc to ground
when a secondary component is malfunctioning.
|
- | Check for a malfunctioning ignition control module. |
- | Check the ignition system wiring for a loose ignition module feed,
ground connection, or damaged system wiring. |
• | Remove the spark plugs. |
• | Inspect the spark plugs for the following conditions: |
- | Check the spark plug for cracks. |
• | If spark plugs are gas or oil fouled, the cause of the fouling
must be determined before replacing the spark plugs. Refer to
Spark Plug Visual Diagnosis
. |
• | Check for the following intermittent ignition system conditions: |
- | Check for an Intermittent CKP Sync or CKP 18X Signal. |
- | Check for an intermittent ignition feed circuit or sensor ground
circuit to the crankshaft position sensor or the camshaft position sensor. |
- | Check for a intermittent 3X reference signal. |
- | Check for a intermittent camshaft position signal |
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Engine Mechanical
|
• | Check engine mechanical for the following: |
- | Check for sticking or leaking valves. |
- | Check for worn camshaft lobe(s). |
- | Check the valve timing. |
- | Check for bent push rods. |
- | Check for worn rocker arms. |
- | Check for broken valve springs. |
- | Check for excessive oil in combustion chamber - Leaking
valve seals. |
- | Check for low cylinder compression. |
• | Check for incorrect basic engine parts. Inspect the following.
Refer to
Engine Overhaul
. |
- | Inspect the cylinder heads.. |
- | Inspect the pistons, etc. |
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Additional Checks
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- | Inspect 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 or decrease in RPM
with little change in actual engine RPM change indicates that EMI
is present. Check routing of secondary ignition wires. Also, check
ignition coils for cracks, carbon tracking, or signs of arcing. |
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