I am hoping you could help me with this problem I am having with my Ford Focus 1.6 Zetec automatic, which I purchased on 16th of April from a local dealer. The car had only 2,266 miles on the clock, and is an ex-Guernsey hire, 6 months old. The day I drove from Weybridge, Surrey, to Swansea, a problem occurred. I had been travelling for about one and a half hours on the M4, and after accelerating quite hard in the fast lane to see how the car responded, and touching 85 mph, I braked lightly, to slow and moved into the middle lane. Thereupon, the car slowed more without any further braking, as if being seized by something, the engine surged a few times then a very loud "clunk" occurred, seemingly from the back of the car, and the car lurched forwards, as if being suddenly released. This happened several times in succession, and was most alarming.
Driving around Swansea at speeds of up to 50 mph was trouble-free, but on the return journey on the M4, after about one and a half hours, moving from the fast to the middle lane, another episode occurred. I returned the car to the dealer, who passed it to Dagenham Motors, the local Ford dealer, for investigation. They have tested the car over 4 days, with no problems detected on the computer, and have been unable to find a fault, even on trips along the A3 of up to 1 hour. Do you have any ideas as to the likely cause of the problem? My feeling is that the drum brakes at the rear of the car had some part to play, but no fault could be found with them. I am now unsure, as to whether I should insist that the dealer or Ford takes the car back as being unsuitable for purpose or whether to keep it and wait and see if the problem happens again.