Hi!
I've been tackling a problem with cold starts with my 2000 2.5 V6 (X25XE) facelift for some time now. Cold start here being any start at engine temperature of 30C or less. For the first 20-30 seconds the engine is overfueling and running rough and there's a strong smell of raw petrol in the cabin. This has happened on every cold start for atleast two months.
There are no fault codes, and the car runs fine for the rest of the day once the morning cold start is done with. There are no fuel leaks from the pipes, hoses, filter, pump assembly, injector rail, injectors, pressure test port or fuel pressure regulator. I ran the fuel pump for 30 minutes independent of engine with no fuel smell from anywhere (intake manifold was open to see injector leakage).
Typical start at ambient temperature 20C:
Upon starting, MID shows a fuel consumption of roughly 10 L/ hour which starts dropping slowly. Rpm is held at about 1300. About 3 seconds after start, engine starts running rough, fuel consumption is at 7-8 L/h. About 5 seconds after start strong fuel smell enters cabin, if car is creeping forward or stationary (smell coming from engine bay). It runs rough for about 20 seconds after this until the fuel consumption has dropped to about 4 L/h then suddenly engine smooths out. Fuel smell starts to fade and disappears in a matter of seconds. All is well for the rest of the day.
BUT, the engine smooths out instantly if the accellerator is pressed in any amount during rough running. Fuel consumption goes down when revs go up. Again if I let off the gas, the rough running returns. If I keep the revs at 1500 as soon as it starts for that 30 seconds there is no fuel smell or rough running at all.Logs dont tell me much, but look at the spark advance when pressing and releasing the throttle .
Here is log and a video of a typical cold start.
Log:
https://www.dropbox.com/s/n0u55lr5wmsds29/cold_start_overfueling.csv?dl=1Video: (sorry for bad audio, the blower vent was pointed to the microphone, and can't really re-shoot today)
https://youtu.be/FLPs0B-wbcw