Diagnostic Method
When a misfire occurs, the engine speed will decreased and the crankshaft position speed will change. Calculate the interval difference value (diagnostic value) from crankshaft position speed by the following formula, and judge whether a misfire is occurring or not comparing the calculated result with judgment value. Counting the number of misfires, if the misfire ratio is higher during 1000 revs, or 200 revs., Judge corresponding cylinders as NG.
| Diagnostic value calculation (Calculate from angle speed) → | Misfire detection every single ignition (Compare diagnostic value with judgment value) → | NG judgment (Misfire occurrence judgment required by the law) (Compare number of misfire with judgment) |
|
|
As shown in the following figure, pick a cylinder as the standard and name it omg 0. And the former crankshaft position speed is named omg 1, the second former crankshaft position speed is named omg 2, the third is named omg 3, etc.
180° Interval Difference Method
| Diagnostic value | domg 180 = (omg 1 - omg 0) - (omg 7 - omg 1)/6 |
Judge as a misfire in the following cases.
|
|
360° Interval Difference Method
| Diagnostic value | domg 360 = (omg 1 - omg 0) - (omg 4 - omg 3) |
| Misfire judgment | domg 360 > Judgment value → Judge as misfire |
720° Interval Difference Method
| Diagnostic value | domg 720 = (omg 1 - omg 0) - (omg 7 - omg 6) |
| Misfire judgment | domg 720 > Judgment value → Judge as misfire |
- FTP 1.5 times misfire (Misfire occurrence level which influences exhaust gas)
Judgment Value (Judge that malfunction occurs when the misfire ratio is high in 1000 engine revs.)
| Malfunction Criteria | Threshold Value |
|---|---|
| FTP emission judgment value | > 1.0% in 1000 revs. |
Time Needed for Diagnosis: 1000 engine revs.
Malfunction Indicator Light Illumination: Illuminates when malfunction occurs in 2 continuous driving cycles.
- Catalyst damage misfire (Misfire occurrence level damaging catalyst)
Judgment Value (Judge that malfunction occurs when the misfire ratio is high in 200 engine revs. (400 ignitions))
| Malfunction Criteria | Threshold Value |
|---|---|
| Catalyst damage misfire judgment value | See MAP 1 FAULT CRITERIA THRESHOLD REFERENCE |
Map 1 Fault criteria threshold for misfire which would result in catalyst damage
| Percentage | Intake air (g(oz)/rev) | ||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|
| 0.16 (0.006) | 0.28 (0.010) | 0.4 (0.014) | 0.52 (0.018) | 0.64 (0.023) | 0.76 (0.027) | 0.92 (0.032) | 1.1 (0.039) | 1.2 (0.042) | 1.4 (0.046) | ||
| Engine speed (RPM) | 1000 | 37.0 | 32.0 | 28.5 | 26.0 | 23.0 | 21.3 | 21.3 | - | - | - |
| 1500 | 35.0 | 29.5 | 25.5 | 22.5 | 21.3 | 21.3 | 21.3 | 18.0 | - | - | |
| 2000 | 32.0 | 22.5 | 22.5 | 18.3 | 14.5 | 10.8 | 10.0 | 9.0 | 8.0 | 5.0 | |
| 2500 | 29.0 | 21.8 | 14.3 | 11.3 | 9.8 | 9.0 | 8.5 | 8.0 | 7.5 | 5.0 | |
| 3000 | 27.0 | 21.8 | 14.5 | 9.8 | 9.0 | 9.0 | 8.0 | 7.5 | 7.0 | 5.0 | |
| 3500 | 24.5 | 18.5 | 10.8 | 6.8 | 5.8 | 5.5 | 5.0 | 5.0 | 5.0 | 5.0 | |
| 4000 | - | 15.3 | 10.0 | 6.8 | 5.5 | 5.0 | 5.0 | 5.0 | 5.0 | 5.0 | |
| 4500 | - | 13.8 | 8.5 | 6.3 | 5.0 | 5.0 | 5.0 | 5.0 | 5.0 | - | |
| 5000 | - | 13.8 | 8.5 | 5.8 | 5.0 | 5.0 | 5.0 | 5.0 | 5.0 | - | |
| 5500 | - | 13.5 | 8.3 | 5.5 | 5.0 | 5.0 | 5.0 | 5.0 | 5.0 | - | |
| 6000 | - | 13.0 | 8.0 | 5.3 | 5.0 | 5.0 | 5.0 | 5.0 | 5.0 | - | |
| 6500 | - | 12.5 | 7.5 | 5.0 | 5.0 | 5.0 | 5.0 | 5.0 | - | - | |
| 6700 | - | 12.3 | 7.3 | 5.0 | 5.0 | 5.0 | 5.0 | 5.0 | - | - | |
These figures indicate the misfire rate (%) in 400 ignitions; for example, 22.5 (%) means 400 (ignition) x 22.5 (%) = 90 (ignition) misfires. This value or more is judged as a misfire.
Time Needed for Diagnosis: 200 engine revs.
Malfunction Indicator Light Illumination: Illuminates as soon as a malfunction occurs.