Every so often once perhaps a week my renault laguna 1.8 dynamique will start and rev up and down between 1800 rpm and 2500 rpm. At the same time the accelerator doesn't do anything when depressed. A light on the dash stays on warning of an electrical fault. If you immediately try restarting no change but leave it half an hour or so and it starts fine.
It renders the car useless with a top speed of around 30 mph and spoils an otherwise ok car. Any ideas???

Steve Wakefield, August 2006

Hi,
I am afraid I don't know the solution to this yet. But I will share with you what I know.
I am having exactly the same problem. The trouble is as you said when you leave it alone for half an hour it goes away! And it doesn't even store a fault code for the technicians to see. Once when I had this problem I called the AA and they connected their computer and found a fault code with the description P0120 'Throttle/pedal position senor switch A circuit'
I took it to the garage but they couldn't find any fault with it so I had to take a day off and drive the car all day to get that problem again. Then I showed it to them and they charged about 300 pounds and told me it was fixed.(they changed the throttle body) But I had the problem the very next day! So I am going to take it back to them. I will let you know if I find anything more.

So far I have noticed the following things.

It only happens after you have driven the car for about at least half an hour.
It always happens when you are on a low gear (first second or reverse)

sam, December 2007