I have a 1999 Ford Focus 1.8 Zetec petrol car which, up until now, has been a very reliable car. A few days ago it started revving even when stationary, hitting 2k at one point and sometimes higher. Now it sometimes idles at the right rev but as soon as a I pull away it ranges from 3k down to 1k. I know when it is high revving when I am driving as I don't need to touch the throttle!

So far I have changed the TPS and left the battery unplugged for an hour and then idled it for 10 minutes hoping to reset the ECU with no joy.

Also the engine temp isn't working accurately anymore either, it stays at the low or cold area of the temp whereas it used to work. I have checked all the fuses too and they are all fine.

No engine management light so no clue there.

Any thoughts anyone? 

Hi Simon, welcome to the Ford Owners Club.

It sounds like you have an air leak on the inlet manifold. Check all hoses and pipes for splits or loose clamps, that are on the inlet manifold.

The engine temprature problem may be unrelated and is possibly just the thermostat stuck in the open position, easy to replace at not much cost.

Thanks Unofix, I will take a look, I did briefly check hoses and things, interestingly, when it started playing up I took a look under the bonnet and the small pipe coming from the rocker cover wasn't plugged into the bottom of the air filter box and the air filter box wasn't screwed down on one side so could mean air was being pulled in from all sorts of angles. I plugged the pipe in and screwed the filter box down properly with no change, which was a shame!