Strange start problem 2006 1.8 Petrol Avensis

[MartinVensis]

Hello! I have a peculiar starting problem with our 2006 1.8 petrol Avensis:

When I try to cold start the car, the engine will crank over for some time but will at best idle rough and die. When I turn the key for the second time, the car will almost always start up fine. Once the engine is running, the engine seems to be working perfectly normal.

If I turn the ignition off, and try starting the car again immediately afterwards, the car starts up just fine.

BUT: If I drive the car for 30 minutes, stop the car and then wait about 30-45 minutes before attempting to start the car again, the following happens when I turn the key:

- The engine will fire up and idle normally for a few seconds, before the idle becomes rough and dies.
- On the second and third attempt, the engine will idle roughly and then die even faster.
- After this the engine will crank, but not start at all, just die when I release the key.
- I then have to wait a few minutes, retry, then wait again, for about 15 minutes before the car finally starts to idle rough, and then pick up RPMs before it starts running normal again and I can drive off.

I've had my car at both the local mechanic + official toyota garage. They first thought the problem was related to the fuel rail, so they replaced this to no help. They then said they did not know, but suggested trying to change the ECU. This was very expensive, and I am not so keen on attempting this before I can guarantee that this will actually solve the problem.

Have anyone else experienced similar problems?