Symptom: a mileage of 92,000 km Peugeot 307 sedan, when the engine hot the car sometimes will stall.
Troubleshooting: First confirm the failure, found the car has appeared twice flameout phenomenon, but when check does not appear this failure. Use lexia 3 pp2000 with latest diagbox 7.76 software to diagnosis, not found the car have fault code, read the data stream is also not found abnormalities, but when scheduling shift car the flameout phenomenon appears again, preliminary analysis of the reasons for this failure may be idling motor abnormal, air intake or MAP abnormal, oil pressure instability or voltage abnormal,EGR abnormal, PCM control abnormal, engine line appears grounding or short circuit and so on.
Road test, continuous driving about 50km not fail, we have cleaned EGR valve and the idling motor, preparing take the car out of the station, idling linked into the D block then flamout, can restart, but at this time hang D block also flamout, from the data stream can see, at cold phase, speed sharp decline, but idling motor control duty ratio increased, LOAD rise, MAP also increased, it meet PCM control logic, but in the long term fuel trim suddenly dropped to -4.2% in this stage. This should be only one possible, that have fuel into the cylinder, but not within PCM monitoring range, resulting in hybrid steam suddenly rich. For this we test the oil pressure, when idling the oil pressure have slight changes, which will not cause the engine to stall, remove the fuel injectors to test, not found leakage; when check the fuel rail, found the vacuum regulator have gasoline droplets; when during the vacuum test, found sometimes gasoline will from fuel rail fuel pressure regulator directly into the intake manifold.
Judged the return spring of fuel pressure becomes soft, then when release the accelerator pedal, the engine load becomes smaller, the degree of vacuum becomes large, the elastic of spring insufficient will cause the diaphragm seal tightly, partially fuel not from injector through vacuum tube into the intake manifold, resulting in hybrid steam suddenly thickens make the engine flameout. Replace the fuel pressure regulator, engine restoration work, troubleshooting.