Diagnostic Method
When a misfire occurs, the engine speed will decrease 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. Count 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 in every single ignition (Compare diagnostic value with judgment value) → | NG judgment (Misfire occurrence judgment required by the law) (Compare number of misfire with judgment value) |
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As shown in the following figure, pick a cylinder as the standard and name it A. And the former crankshaft position speed is named B, the second former crankshaft position speed is named C, the third is named D, etc.
| Diagnostic value | 180 degree interval difference = (A - B) - (B - C) |
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Judge as a misfire in the following cases.
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| Diagnostic value | 360 degree interval difference = (B - A) - (D - C) |
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| Misfire judgment | 360 degree interval difference> Judgment value → Judged as misfire |
| Diagnostic value | 720 degree interval difference = (A - B) - (E - F) |
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Judge as a misfire in the following cases.
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• 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 diagnostic value | ≥ 24 x 100/2000% in 1000 revs. (CVT model) ≥ 35 x 100/2000% in 1000 revs. (MT model) |
Time needed for diagnosis: 1000 engine revs.
Malfunction indicator light illumination: Illuminates when malfunction occurs in 2 continuous driving cycles.
• Catalyst-damaging misfire (misfire occurrence level that will damage catalyst)
| Malfunction | Criteria Threshold Value |
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| Catalyst-damaging misfire diagnostic value | ≥ Value from Map |
| Percentage (%) | Charging efficiency (%) | ||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 15 | 30 | 45 | 60 | 75 | 90 | 105 | 120 | 135 | 150 | 165 | 180 | ||
| Engine speed (rpm) | 700 | 25 | 25 | - | - | - | - | - | - | - | - | - | - |
| 1000 | 25 | 25 | 25 | 25 | 25 | 25 | - | - | - | - | - | - | |
| 1500 | 25 | 25 | 25 | 25 | 16.75 | 16.75 | 16.75 | - | - | - | - | - | |
| 2000 | 25 | 25 | 25 | 25 | 16.75 | 14.25 | 12.5 | - | - | - | - | - | |
| 2500 | 25 | 25 | 19.75 | 17 | 14.25 | 12.5 | 11 | 11 | - | - | - | - | |
| 3000 | 25 | 25 | 19.75 | 17 | 14.25 | 12 | 10.5 | 10 | 7.75 | 6 | - | - | |
| 3500 | 25 | 25 | 19.75 | 17 | 14.25 | 11 | 9 | 7.75 | 6 | 5 | 5 | 5 | |
| 4000 | - | 25 | 19.75 | 17 | 14.25 | 11 | 8.25 | 6.25 | 5 | 5 | 5 | 5 | |
| 4500 | - | 25 | 17.5 | 14.25 | 12.5 | 9 | 6.75 | 5 | 5 | 5 | 5 | 5 | |
| 5000 | - | 25 | 16.75 | 12.5 | 11 | 8.25 | 6 | 5 | 5 | 5 | 5 | 5 | |
| 5500 | - | 25 | 16 | 12 | 11 | 7.25 | 5 | 5 | 5 | 5 | 5 | 5 | |
| 6000 | - | 25 | 15 | 11 | 11 | 6 | 5 | 5 | 5 | 5 | 5 | 5 | |
| 6500 | - | 25 | 12.5 | 8.75 | 8.75 | 5 | 5 | 5 | 5 | 5 | 5 | 5 | |
| 6800 | - | .25 | 11.25 | 7.5 | 5 | 5 | 5 | 5 | 5 | 5 | 5 | 5 | |
Time needed for diagnosis: 200 engine revs.
Malfunction indicator light illumination: Illuminates as soon as a malfunction occurs.