Purpose
To determine the cause of rough engine idle The Injector Disable Tests can only be done with the EST; MasterDiagnostics® software is required.
The Injector Disable Tests allows the technician to shut-off injectors to determine if a specific cylinder is contributing to engine performance. Injectors can be shut off one at a time, alternative cylinders at a time
or alternative cylinders plus one.
Alternate cylinders are every other cylinder in firing order.
Firing order: 1–5–3–6–2–4
When all cylinders are active, the contribution of each cylinder is 17% of its overall effect to maintain governed speed. When three cylinders are shut off, contribution of each remaining cylinder is 33% of its overall effect to maintain governed speed. The technician should monitor fuel rate and engine load.
NOTE: The Relative Compression Test 12 should be done after doing the Injector Disable Test 11 to distinguish between an injector or mechanical problem.
Tools
• EST with MasterDiagnostics® software
• EZ-Tech® interface cable
NOTE: Before doing the Automatic Test or Manual Test for injector disable, make sure Tests 1 through 10 were completed and the following conditions are maintained:
• Make sure accessories are turned off. (Example – engine fan and air conditioning) Items cycled during this test could corrupt the test results.
• Maintain engine idle.
• Keep EOT within a 2 °C (5 °F) range from the beginning to the end of the test. EOT affects injection timing; too much of a change in EOT temperature could corrupt the test results.
Automatic Test – Auto Run
The Automatic Test is best done when comparing cylinder to cylinder test data.
NOTE: If MasterDiagnostics® software does not have the Automatic Test (auto run feature), Injector Disable
– Manual Test in Section 3 for procedure to compare cylinder to cylinder.
NOTE: Do KOER Standard test before doing this test.
1. While engine is running, open D_KOER_ IDT_ I6.ssn to monitor engine operation.
2. Select Diagnostics from menu bar.
3. Select I6 Injector Disable Test from drop down menu.
NOTE: The EOT indicator will change from red to green when engine temperature reaches 70 °C (158 °F) or higher.
• If the EOT indicator is red, erroneous comparisons are likely from cylinder to cylinder.
However, when diagnosing a cold misfire, a technician can listen to tone changes from cylinder-to-cylinder.
• When the EOT indicator is green and the engine temperature is 70 °C (158 °F) or higher, fuel rate and timing are more stable, making comparisons from cylinder to cylinder more accurate. Overall engine operation is more stable.
4. Select Auto Run.
NOTE: While running the engine, listen for sound variations from cylinder to cylinder.
NOTE: If any injectors are removed and reinstalled or replaced, test drive vehicle for 20 miles before checking for misfire or rough idle.
During Auto Run, injectors are shut off one at a time (1 through 6 in numerical sequence). Baseline data and
results for each cylinder is displayed in the window (Text View) for I6 Injector Disable Test Results. Test data for each injector can also be viewed by selecting the (Graph View).
5. Record data from window (Text View) on Diagnostic Form.
• If deviation values for average fuel rate and average engine load are less than the cut off values for fuel rate and engine load, the injector is suspect for weak cylinder contribution.
• If only one deviation value is less than a cut off value, do not suspect that cylinder.
• If a suspect cylinder(s) is identified, do Test 12 Relative Compression to distinguish between an injector or mechanical problem.
• If Test 12 shows that cylinders are mechanically sound, but the Injector Disable Test shows that one or more cylinders are bad, continue with step 6.
6. Remove valve cover following procedure in Engine Service Manual.
7. Replace faulty injector(s) following procedures in the Engine Service Manual.
8. Test drive vehicle for 20 miles to purge air from ICP system and fuel supply system. Check for rough idle.
9. If rough idle continues, do the Injector Disable Test again.
Possible Causes
• Failed connection from wiring harness to injector solenoid
• Open or shorted wiring harness to injector solenoid
• Failed solenoid on fuel injector
• Scuffed or damaged injector
• Failed IDM
• Failed ECM
Manual Test
The Manual Test is best done when diagnosing each cylinder for cold misfire, considering EOT changes.
The EOT indicator will change from red to green when engine temperature reaches 70 °C (158 °F) or higher.
• If the EOT indicator is red, erroneous comparisons are likely from cylinder to cylinder.
However, when diagnosing a cold misfire, a technician can listen to tone changes from cylinder-to-cylinder.
• When the EOT indicator is green and the engine temperature is 70 °C (158 °F) or higher, fuel rate and timing are more stable, making comparisons from cylinder to cylinder more accurate. Overall engine operation is more stable.
Shut off one injector at a time and listen for changes in exhaust tone.
NOTE: If any injectors are removed and reinstalled or replaced, test drive vehicle for 20 miles before checking for misfire or rough idle.
1. While engine is running, open D_ KOER_IDT_I6.ssn. to monitor engine operation.
2. Select Diagnostics from menu bar.
3. Select I6 Injector Disable Test from drop down menu.
NOTE: The EOT indicator will change from red to green when engine temperature reaches 70 °C (158 °F) or higher.
• If the EOT indicator is red, erroneous comparisons are likely from cylinder to cylinder.
• When the EOT indicator is green and the engine temperature is 70 °C (158 °F) or higher, fuel rate and timing are more stable, making comparisons from cylinder to cylinder more accurate. Overall engine operation is more stable.
4. Select cylinder number and select Run. (Injector selected will be disabled and engine noise should change.)
5. Select Normal Operation. Injector will be enabled and engine noise should return to previous state of operation.
6. Repeat steps 4 and 5 for the remaining cylinders.
NOTE: Listen for tone changes from cylinder to cylinder.
NOTE: If any injectors are removed and reinstalled or replaced, test drive vehicle for 20 miles before checking for misfire or rough idle.
