December 8, 2010, 10:39 am
[quote name='MrrNoName' timestamp='1291487821' post='105802']
Hi, I had this EXACT same problem on my mk4 fiesta, over revving when changing gear and revving itself down the road. but couldent re-produce the results when parked no matter how hard I tried!! (VERY ANNOYING) lol
I scanned the car for codes and got "Throttle Position Sensor (TPS) Out of Range".
however you have to remember that this only tells you where the ECU detects the problem. not what is actually faulty.
I discovered that by unplugging the battery (this is probs to give the same effect as what the mechanic said to you) for 20 mins the car would then run fine for 3 days, but after that the problem would return and the car would need to be reset again.
I also discovered that by unplugging the tps the car would run rough but not over rev. Must be the TPS i thought?
I replaced the TPS but this did nothing, the car would still over rev when clutching in and drive itself down the road.
point of the story
try changing the tps first as you can purchase one cheap as chips on ebay, but that might well not fix the problem. other things to consider are the wiring to the tps (if the pins are corroded it can affect the voltage and cause incorrect readings) or worst of all a faulty pcm (highly doubt that tho).
others stuggested at the time that it could be the idle speed control valve or vehicle speed sensor.
Unfortunately i never found a cure for the problem and after taking it to ford (who told me my car mat was getting caught OVER the pedal??!??!) and other garages (who couldent fix it) i ended up resetting the car every 3 days until it was written off (not my fault i might add
hope this helps
Replaced tps this am all seems fine now thanks for the help folks...mind you 68 quid at stealers and 20 on ebay is a bit of a difference don't you think?