It may be possible to simply cut the split section off then heat the pipe and push it back on to the barb for a permanent fix, I did this on my old 1.4 and it's still OK.

ok guys, an update:

 

its worse than before now. the revs gets so slow that the engine stalled mid driving.

You need to reset the fuel trim after a fix, this means clearing the dynamic map so the ECU can learn the new fuel/air ratio.

1 minute ago, sepulchrave said:

You need to reset the fuel trim after a fix, this means clearing the dynamic map so the ECU can learn the new fuel/air ratio.

do you mean disconnecting the battery for few minutes?

I left my battery disconnected for 10 minutes and then went for a drive, the problem was still there for me (although it did seem to be less severe). Is that long enough for the ecu to completely lose power?

 

I'm not sure on the level of capacitance in a cars wiring, but I imagine it's not insignificant

how about putting the neg and plus wires tgether to completely drain the power that is still left behind?

Frankly you can't hope to work on modern tackle without some form of basic code reader to clear faults with and reset the ECU.

 

I am told that the ECU does not require a permanent live any more so disco'ing the battery may not work like it used to.

Just driving the car more will re-educate the system about the 'new normal'.  If the vac line cracking was actually leaking air, and something has changed.

 

I have an obd reader and it shows no codes at all

Edited 26 March, 20215 yr by BrumTom_

9 hours ago, BrumTom_ said:

I have an obd reader and it shows no codes at all

 

You can still clear codes, doing this will reset the ECU even though there are no codes to clear.

disconnect the negative from the battery for couple of minutes then connected it back up and went for test drive, it was still doing the rough idling. 

This is a very old thread now but, given no resolution was posted, I thought other Mk2 Fabia owners might like to hear that I found a cure for this issue on my car. Hence I had an identical problem with my 2010 Fabia htp 70; i.e. revs at idle or with clutch depressed oscillating between 1000 and 400, almost stalling on occasion. In the hope of resolving this I’d done everything suggested here, including locating and repairing the infamous split servo pipe (yes mine was split too), but like here, to no avail. However, I was able to replicate the pull the accelerator pedal up with the toe effect, also noted here, which often resulted in a temporary cure even though, strangely, there was no actual movement in the pedal. In fact, it worked just as well pushing the pedal to the side. The answer was a replacement used accelerator pedal off eBay for less than £20. All you need is a torch, and a 1/4 inch socket set with a 10mm socket. There are just three nuts and one electrical connector involved; really straightforward. And you don’t need to mess about reprogramming the ECU; just attach the replacement pedal and drive off. The engine adapts in a few minutes. I hope this helps someone.