My 53 plate Corolla, on 82,000 miles, keeps losing power and then cutting in again, usually once during say a 20 mile run, but now getting more frequent; not funny when trying to enter a roundabout with traffic approaching! No warning lights come on; it has been regularly serviced, and fuel cleaner put in at each service. Last service was last August, when the air filter was also changed. The Toyota dealer thinks it is valves sticking, but they are ok when they test them, so they said to "let the fault develop" before they can find the cause - but the thought of it happening during an overtake or on a motorway makes me nervous.

Any advice would be welcome: I don't feel I can sell it in this state, but an expensive repair might be more than the car is worth.