306 1.4 (y/2001) loss of power and intermittent starting

[nick3000]

5 Months ago the car started having intermittent problems starting (especially when weather was cold) - the car would stall if the accelerator was not applied. The engine would need extra petrol for up to 5 minutes from turning the key, if foot was taken off then the revs would get lower and lower as less gas applied until it stalled.

A couple of months later the car had a full service (plugs, oil, filter etc) and at that point my mechanic did have a hunch that it was a lambda oxygen sensor, which cured a similar problem on another 306. This did not cure it.

Now a second problem has occurred (4 months after start of original) where there is a sudden loss of power (mainly but not always) under engine load. The loss of power stays for 5-10 seconds and then acceleration resumes. There is no stuttering, jumping or noises or other visible signs apart from you begin to slow down which is a major problem when going up a hill.

The main problem is that no error codes have been logged by the CPU – this has been checked by 2 garages of which one is an electrical specialist.

The car is otherwise in good working order, but I don't want to throw money at a problem which cold have a simple solution.