Ford Fiesta Revving Problem..

[Kazlok]

Hey guys!

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
  

During the emissions test they need to keep the engine around 2.5k-3k revs for a sustained period of time, but unfortunately it cannot be kept stable.

Things we have tried are :-

1. Cleaning/Changing the IAC (Idle Air-control valve)
   
2. Cleaning/Changing the TPS (Throttle Position Sensor)
   
3. Checked the vacuum pipes
   
4. Removed the ECU fuses for 10 mins, then plugged back in
   
5. Disconnected battery for 30 mins, idled for 10 mins, drove for 10 miles
   

Starting to run out of ideas now as to what could be causing the problem, something else that can apparently do it is a sensor related to or nearby the power steering column ( I can't remember the exact one, it's been a long day haha)

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..

[eyemdee]

I remember having a similar problem with a Ka3 some years ago. When lifting off the throttle to change gear the revs did not drop and remained high all the time the car was moving. As soon as the car stopped moving the engine would return to idle. It was fixed under the used car warranty by "reworking" some wiring under the bonnet above the steering column and against the bulkhead.

Sorry I cannot be more specific but if I remember rightly it looked like a component in that area had its connections bypassed but the dealer at the time just said that it was a standard modification at the time.

[Kazlok]

I remember having a similar problem with a Ka3 some years ago. When lifting off the throttle to change gear the revs did not drop and remained high all the time the car was moving. As soon as the car stopped moving the engine would return to idle. It was fixed under the used car warranty by "reworking" some wiring under the bonnet above the steering column and against the bulkhead.

Sorry I cannot be more specific but if I remember rightly it looked like a component in that area had its connections bypassed but the dealer at the time just said that it was a standard modification at the time.

That's great, we're gonna have a look at it later today to see if we can find the same bit your talking about :)

[eyemdee]

Have a read of this - I'm not sure that it helps but I am fairly sure that this was the problem on our old Ka.

http://www.honestjohn.co.uk/forum/post/index.htm?t=22353

[Kazlok]

It was a good read but unfortunately it didn't solve the problem..

However, whist looking for a different sensor we discovered a pipe/tube had become disconnected which should of been attached to the fuel injection system?

Apparently this has been disconnected since my nan's had it (about 7 years lol)

Thanks for the support though, maybe this will help someone else out who's having the same problem :)