I have a Ford Focus mk1 1.8 tdci 100HP from 2004. The car functions perfectly, but starting one or two weeks ago the car started to stall ONCE in the morning (cold start in the summer). I crank the engine, it starts and after one or two seconds it stops. I crank it again (takes one or two seconds longer than usually) and it starts just like usual. After this incident the car works fine all day.

I scanned the vehicle using my obd device and it shows no DTCs (except one for the inlet AC motor which shows up from a long time, but I think it's unrelated to this issue). Fuel pressure matches the desired fuel pressure, the injectors seem to be working fine. I looked for the crankshaft position sensor and the device says it is syncing its position.

This makes me think that the engine is ok and that a filter may be the problem. I plan on changing the air and fuel filters soon.

Do you agree with my assessment? Do you think something else could be a problem? If yes, what should I test to further diagnose the problem? Thank you!

Update: It turned out to be a clogged fuel filter issue. I changed the diesel filter and the problem is gone. It was bizarre since the fuel filter didn't look too bad, just half of it was yellowish, but it was enough.

  • it sounds like a temperature sensor is malfuctioning so your engine changes from rich fuel mixture to lean too soon after startup,so take a look at the sensor readings when you start the engine(it might be the oxygen sensor too) Commented Aug 13, 2019 at 17:02
  • What temperature sensor should I look into? Cylinder head, cooling fluid? You speak about the O2 sensor on the input manifold? Commented Aug 13, 2019 at 17:38
  • o2 sensor is on/after the exhaust manifold,temp sensor is probably on the cylinder head.i do not know your car so i made a comment and not an answer. Commented Aug 13, 2019 at 17:45
  • Clean the throttle body. Ford tends to be sensitive to a dirty throttle body.
    – vini_i
    Commented Aug 13, 2019 at 18:28

1 Answer 1


It turns out it was a fuel filter issue. I replaced the fuel filter (which had about 15000km) and the problem is gone. The car starts smoothly in the morning. Therefore, this is definitely a thing to try if you encounter the same problem: stall after cold start with no other symptom whatsoever (no error code either).

I opened the fuel filter and it wasn't disastrous, but half of it was yellowish and probably didn't allow the fuel to flow as it should.

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