Automotive Troubleshooting Engine Stall and Hesitation 2 of 2


<2> Narrow down fuel system
• Fuel pressure inspection
When the symptom occurs, check whether the fuel pressure exists or not.
In the case where fuel pressure exists
• Injector and injection control and the relevant area
• Ignition system
In the case where fuel pressure does not exist
• Fuel pressure feed system including the fuel pump
• Fuel pump control system
• Air fuel ratio inspection
Using a hand-held tester, judge the A/F condition when the symptom occurs based on the O2 sensor voltage.
When it is not possible to narrow down the cause to the ignition and fuel systems, inspect for causes other than those relating to engine control.
• ECTs
• Mechanical cause in the engine
• The cause of A/F rich and lean that is not observed with the tester.
Narrow Down Using Tachometer
During a road test, narrow down whether the malfunction cause is in the ignition primary side or not by observing how much the indicator of the tachometer drops when the problem symptom recurs. In the tachometer or tune up tester that counts the number of counter electromotive generated in the ignition primary coil and converts it into the engine speed, if a malfunction occurs in the ignition primary system, the indicator of the tachometer distinctively drops.
Inspection methods
Inspect the movement of the indicator in the tachometer when hesitation occurs.
• When the indicator dramatically drops: A malfunction in the primary ignition system
• When the indicator gradually drops: A malfunction in an area other than the primary ignition system
This inspection cannot be performed in the system where the ECU counts the Ne signal, etc. and sends the engine speed to the tachometer.

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