I have a problem with my 52 plate 1.3 duratec fiesta I was  wondering if any one has any ideas as to what’s wrong with it first of all the symptoms are on cold start the idle is at 1500 rpm it use to be 1100 rpm sometimes when I’m driving I take my foot off the throttle and the revs stay the same and don’t drop this is what I’ve done so far trying to fix it

New engine idle control valve
New throttle position sensor
New map sensor
New lambda sensor
Throttle body inspected can’t fault it
Double and triple checked four times for a vacuum leak

Anyone seen anything like this before?

thank for any advice I’m lost

Andy

Checked the oil breather pipe under the manifold?  Can be hard to spot the splits in those.

It has two breather pipes one goes straight to the air filter and the other is from the a valve on top of the rocker I forgot to mention I’ve also replaced the the breather valve from on top of the rocker 

13 hours ago, Andy1972 said:

It has two breather pipes one goes straight to the air filter and the other is from the a valve on top of the rocker I forgot to mention I’ve also replaced the the breather valve from on top of the rocker 

It's the thin one that goes straight to the manifold that usually cracks and creates a vac leak, regardless of throttle position.  Did you replace all of the thin pipes from it or just the valve on top of the rocker?

Ive had all pipes off and inspected they are as good as new

But ill check again lol 

 

thanks for the help

Lol, no need if you've already checked them.  It does sound like a vac leak though.  

I wonder if the evap valve could be sticking...

Also a very long shot but if it's mainly happening when cold, the coolant temp sensor may be worth checking as well.

Ive disconnected the evap valve and the idle is still high am i chasing the wrong thing with the idle should it be at 1400-1500 on cold start and i fitted a cheap thermostat housing from ebay a few months ago as the old one was leaking so its new bit i could pull the sensor out and refit the old one but the dash shows a good reading

No, you're right, the cold idle shouldn't be that high.  I suppose you could live with it as long as it generally drives ok and isn't creating too many emissions for the MOT test, but it wouldn't have been like that when new.

Usually with a fault like this we'd recommend some diagnostics such as Forscan but the 1.3 is a more conventional setup than the other Mk6 petrol's so I'm not sure how effective Forscan would be.  Even a basic OBD2 reader should show things like coolant temp, throttle position and fuel trims (which indicate a vac leak) so that may still be worth a try if you can borrow one.

the idle speed goes back to normal once its ran for a while and starts to warm up in fact it drops as low as 750 rpm I did fit a cheap thermostat housing off Ebay about a month before this started happening is it possible that the cheap sensor that came fitted with the housing could be causing all more problems?

2 hours ago, Andy1972 said:

the idle speed goes back to normal once its ran for a while and starts to warm up in fact it drops as low as 750 rpm I did fit a cheap thermostat housing off Ebay about a month before this started happening is it possible that the cheap sensor that came fitted with the housing could be causing all more problems?

It's definitely possible.  Though not a common fault.  If you can borrow an OBD2 tester to check it's readings when cold that would be ideal.

My original fault was the car would rev on its own at random 1500 rpm and sometimes 2500 rpm I changed the idle control valve and now the idle is high and sometimes not very often when I off throttle and press the clutch the revs stay at what ever they were so the problem isn’t the same as originally I’m starting to think I’ve bought and fitted a duff idle control valve 🤦🏻

🤦🏻 just undone the plug on the wiring harness that leads to the head and intake system the git was as green as fairy washing up liquid inside any way all cleaned up so let’s see how that goes

It could be the fuel (maybe) it doesn't like E10?????

Is it a fully electric throttle? If so it may need resetting

Is the ignition system in good condition?

If unburnt fuel is reaching the catalyst the O2 sensor will raise the revs to burn it off

1 hour ago, Andy1972 said:

🤦🏻 just undone the plug on the wiring harness that leads to the head and intake system the git was as green as fairy washing up liquid inside any way all cleaned up so let’s see how that goes

Just seen this, best to cut back wiring until good and replace

Well I thought I’d found my problem the wiring loom but the fault came back I have now after many months finally figured it out something  that hadn’t even crossed my mind my problem was the the power steering pressure switch faulty causing the problem all the time