Detonation/Spark Knock
Inspection/Test
| Action
|
DEFINITION: A mild to severe ping, usually worse under acceleration.
The engine makes sharp metallic knocks that change with throttle
opening.
|
Preliminary
|
|
Fuel
System
|
• | Inspect any items which may cause an engine to run rich, long
term fuel trim is significantly in the negative range. Refer to Diagnostic
Aids for DTC P0172. |
• | Inspect any items which may cause an engine to run lean, long
term fuel trim is significantly in the positive range. Refer to Diagnostic
Aids for DTC P0171. |
|
Ignition
System
| Inspect
the spark plugs for proper heat range and reach. Refer to
Ignition System Specifications
.
• | Inspect for proper ignition voltage output using the following
steps: |
1. | Attach the J 26792
Spark Tester to engine ground. |
2. | Connect the spark plug end of the spark plug wire to the J 26792
. Connect the other end
of the spark plug wire to the coil being tested. |
3. | Connect the spark plug end of the companion spark plug wire to
ground. The companion spark plug wire is the wire attached to the corresponding
coil tower. |
4. | Crank the engine while observing the J 26792
. A spark should be observed. |
5. | Repeat the above steps for each coil. |
• | If spark is not present at the coils, inspect for the following
conditions: |
- | Coils--Cracks, carbon tracking/arcing, or a resistance value
outside the specified range. |
Coil Resistance 5000-8000ohms (5K-8Kohms) - | Spark Plug wires--signs of arcing, cross firing, cracks,
carbon tracking, plug boot damage, pinched, improper routing, or a resistance
value outside the specified range. |
Spark Plug Wire Resistance 9868ohms per meter (3000ohms per foot)
| Important: : Spraying the secondary ignition wires with a light mist of water may
help locate an intermittent condition. Ignition voltage will arc to ground
when a secondary component is faulty.
|
- | Defective ignition module |
- | Ignition system wiring--Loose ignition module feed or ground
connection, or damaged system wiring. |
• | Remove spark plugs and inspect for the following conditions: |
- | Burned or damaged electrodes |
- | Improper heat range or reach |
• | 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 Inspection
. |
|
Engine
Cooling System
| Inspect for obvious overheating conditions:
• | Restricted air flow to the radiator, or restricted water flow
through the radiator. |
• | Inoperative electric cooling fan circuits |
|
Engine
Mechanical
|
• | Inspect for incorrect engine parts, such as the following basic
components: |
- | Camshaft and valve train components |
|
Additional
|
• | Test for proper exhaust gas recirculation (EGR) system operation.
Refer to
DTC P0401
. |
• | Inspect the transaxle range switch input with the vehicle in
drive and the gear selector in drive or overdrive. |
• | Test the torque converter clutch (TCC) operation. TCC applying
too soon can cause the engine to spark knock. Refer to
Torque Converter Diagnosis
in Automatic Transaxle. |
• | If scan tool readings are normal and there are no engine mechanical
faults, fill the fuel tank with a known quality gasoline that has a minimum
octane reading of 87 and re-evaluate vehicle performance. |
|