I've had an issue with my Fiesta (1.25 Zetec) not passing its M.O.T. due to it not being able to partake in the Emissions test, reason being, the revving is completely unstable.
It's had this problem since I can remember and only now have I had an issue with the M.O.T.
In short the problem is like so.
- While idle the car revs around 1k-1.2k
- Upon depressing the throttle the engine revs quickly up-to around 3k then up-to 4k. If during this the throttle is disengaged the engine keeps revving as if I am tapping the throttle, even though I am doing nothing. (Occasionally it resets to idle but putting it into gear and finding the bite quickly restores it)
- During a gear change the engine occasionally over-revs
Things we have tried are :-
- Cleaning/Changing the IAC (Idle Air-control valve)
- Cleaning/Changing the TPS (Throttle Position Sensor)
- Checked the vacuum pipes
- Removed the ECU fuses for 10 mins, then plugged back in
- Disconnected battery for 30 mins, idled for 10 mins, drove for 10 miles
Just wondered if anyone else has had this problem and had an idea as to what could be causing it, apparently it's quite common and can be lots of little things..