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Mk6 fiesta wont idle


Truxx
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hi.
 looking for a little advice.
few days ago my mk6 1.4 zetec fiesta stalled on me while reversing out of a parking bay. it started straight back up but was idling at 3.5k rpm.

had a look under bonnet next day and only thing i could find wrong was the breather pipe had come off the pcv. when i put it back on the car wont idle at all unless i keep the revs up manually? 

ive checked all vacuum pipes and there's non split. decided to replace my timing belt while i was stripping things down anyway so removed quite a lot of parts including inlet manifold and still cant find anything wrong.

the pcv valve isnt jammed. inlet manifold cleaned. the butterfly valve opens a little while cranking and car revs up fine so i dont think thats the fault...?

any ideas? 

there no management lights on so no faults stored in the ecu either.

when i stalled it it was quite abrupt and kind of bounced to a stop lol  but cant thunk of anything that would harm...

appreciate any advice. 
id rather not just replace random parts in the hope itll fix it as that tends to get expensive lol...

thanks
dave

    

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  • 3 weeks later...
52 minutes ago, Truxx said:

Thanks for the huge responses :) much appreciated.

Lol. Chances are nobody knows what's wrong, it's not something you can exactly diagnose without looking at it in person. People don't want to just hazard a guess. Have you got any closer yet?

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Im just suprised someone hasn't had this issue already.

Replaced throttlebody / map sensor/pcv valve/ fuel pressure regulator and still no different. 

Idles super high with vacuum pipe(inlet manifold to pcv) unplugged from pcv valve but wont idle without throttle with vacuum pipe connected to pcv even with pcv unplugged from block lol.

Very annoying. 

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20 hours ago, Truxx said:

Replaced throttlebody / map sensor/pcv valve/ fuel pressure regulator and still no different.

It sounds like you have eliminated almost everything. It is hard to see it not being a throttle control problem. The only bits left are the ECU and the wiring between it and the throttle.

There was a case where an ECU was damaged by a faulty throttle body:

I hope it is not that, that would be a real pain. But more investigation of the throttle body, and how it moves, might help. Removing the vacuum pipe effectively by-passes the throttle.

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On 09/08/2017 at 9:10 AM, Tuha said:

Hello,

try to clean throttle and stepper motor in it.

you can use IPA (isopropyl alcohol to do that). 

Cleaned it already and still no different so i replaced and still no different lol.

 

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18 hours ago, Tdci-Peter said:

It sounds like you have eliminated almost everything. It is hard to see it not being a throttle control problem. The only bits left are the ECU and the wiring between it and the throttle.

There was a case where an ECU was damaged by a faulty throttle body:

I hope it is not that, that would be a real pain. But more investigation of the throttle body, and how it moves, might help. Removing the vacuum pipe effectively by-passes the throttle.

Any easy way to check ecu?

Had diagnostics on it today and even used live data but theres nothing i can find out of ordinary.

Ill try live data again tomorrow and spend some more time on it but its not looking good.

The car is an old heap but i use it to deliver chinese food and its perfect car for it. Im now having to use my evo 8 to deliver and its getting costly lol.

The symptoms indicate to me that theres a vacuum leak but i just cant find any faults in the vacuum system at all .

Ill rig up a boost gauge tomorrow aswell but even thats not gonna help much as the car only runs when i keep on throttle lol.

 

The search continues...

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1 hour ago, Truxx said:

the car only runs when i keep on throttle lol.

I am assuming it has an electric throttle body. The 1.3, and earlier 1.4s, had a cable operated throttle body and an Idle Control Valve. These ICVs were prone to jamming and preventing it from idling.

Maybe it would help if you were a bit more detailed about how it runs and stalls. From what you say, it will start and stay running if you apply a bit of throttle, and drives ok once going. But then as soon as it goes into neutral, and you release the throttle pedal, it stalls. Does it stall straight away, or hunt up and down a bit first?

Can careful throttle control keep it steady near to normal idle rpm, or does it stall if it drops below a certain rpm? If it does the latter, maybe it would be worth replacing the crank sensor, or it could even be an ignition problem.

Vacuum leaks will be more likely to speed up the engine, as you found.

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18 hours ago, Tdci-Peter said:

I am assuming it has an electric throttle body. The 1.3, and earlier 1.4s, had a cable operated throttle body and an Idle Control Valve. These ICVs were prone to jamming and preventing it from idling.

Maybe it would help if you were a bit more detailed about how it runs and stalls. From what you say, it will start and stay running if you apply a bit of throttle, and drives ok once going. But then as soon as it goes into neutral, and you release the throttle pedal, it stalls. Does it stall straight away, or hunt up and down a bit first?

Can careful throttle control keep it steady near to normal idle rpm, or does it stall if it drops below a certain rpm? If it does the latter, maybe it would be worth replacing the crank sensor, or it could even be an ignition problem.

Vacuum leaks will be more likely to speed up the engine, as you found.

It has the electric throttlebody. No throttle cable.

If i start it and try to keep revs stable near idle it still wont idle steady its surging up and down. Keeping the revs at idle speed it starts to die the you hear the throttlebody open as it takes a gulp of air then closes and cycle repeats so definately points to vacuum to me?

Havent tried driving it all this is just being done on my drive but when it stalls it just stalls no stuttering soon as i release the throttle it out.

Ill try replacing the crank sensor next since its cheap.

So today itook the pcv valve off my vitara jeep to compare it with the 2 fiesta ones i have. I can blow through both fiesta pcv in either direction? 

Vitara one only lets me blow through one way?  Bearing in mind the only fault i could find when this first happened is that the vacuum pipe had come off the pcv valve?

Appreciate all the replys.

 

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14 hours ago, MJNewton said:

A vacuum leak will result in high positive fuel trim values so they are worth checking. There will be more of an effect when idling compared to at high(er) revs. 

I will look more into this but at moment car has no aux belts,coolant,alternator etc so cant keep it running for too long. 

Back to normal shifts on the 18th so ill get stuck in properly then lol.

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1 hour ago, Truxx said:

I can blow through both fiesta pcv in either direction? 

The primary function of a PCV valve is to have an orifice, usually variable size, that allows normal blow-by gas flow through, but does not allow the low inlet manifold pressure, especially at low load, to pull too much air through.

A non-return valve is a 2nd, and optional part of the valve. It is to prevent hot backfire gas from entering the crankcase, and a gauze mesh, or other design features may prevent this.

So flow in both directions is not necessarily wrong. It is hard to test the normal operation, it needs a good suction (from the engine, or maybe from a powerful hoover?) to close down the orifice and restrict the flow. Without this suction, it should be fully open.

So it is possible that a jammed PCV is causing the problem, allowing too much suction into the crankcase, thus too much blow-by into the inlet manifold, and making it impossible for the engine to run at low air flow (idle). If the PCV had also jammed shut initially, pressure build up in the crankcase could have blown the hose off the valve, if that is the weakest link.

High rpm just by removing the PCV hose also suggests a sticking PCV, it should close down to reduce the flow.

Try removing the PCV to crankcase hose, blocking the inlet to the PCV, and leaving the crankcase vent hose open to atmosphere. (Be careful what you block the PCV with, anything sucked in there can go straight into the engine!)

 

 

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  • 8 months later...

Just wondering if you managed to get to the bottom of this problem, my partner is having the same issue with her MK6 1.25 Fiesta.  PCV & breather hose replaced car won’t idle, put the old breather hose on and it idles fine. 

Not really up for changing everything on the car as it’s her first car and is only a cheap run around for now

Thanks in advance  

 

 

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  • 11 months later...

@MJH I'm in exactly the same position as you. Had a split pcv hose so I replaced that and replaced the PCV valve today. Car judders and runs rough on idle. Did you find a resolution?

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On 5/10/2018 at 8:44 PM, MJH said:

 PCV & breather hose replaced car won’t idle, put the old breather hose on and it idles fine. 

 

10 hours ago, GLM said:

Had a split pcv hose so I replaced that and replaced the PCV valve today. Car judders and runs rough on idle.

There looks to be a linking problem of a leak of air into the inlet manifold from a damaged hose or faulty PCV, then it idles slowly, roughly or not at all when the pipe or valve is replaced.

The ECUs on modern cars continually adjust themselves. If there is air leak for long enough, then the long term fuel trims will self adjust, and possibly also the learnt throttle valve positions. In most cases, if the car can be used like this, it should slowly re-adjust. However there is a problem, that the learnt values can slowly be moved out by a gradually increasing leak over time. But then the sudden change back to no leak is beyond the normal acceptable self-learning range.

There will be a "Reset adaptions" or "Reset module" facility in the ECU that should set it back to initial settings, then it should be able to learn the current values needed. This can be done either at a garage with IDS (usually main dealers!), or with a good, Ford specific diagnostic system like Forscan.

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@Tdci-Peter First of thanks for taking the time to write an in depth response. Resetting KAM and fuel trims etc is something I had already explored. I've had the battery disconnected for a few hours and touched both leads together to drain any remaining stored power and I've also removed the KAM related fuse for a few hours. None of which made a difference.

I've now replaced the MAP sensor below the throttle body and had a really good look around the car for anything obvious. The idle is still lumpy and when sitting in the car every 2-3 seconds you can feel it judder, if I apply a very small amount of throttle (to about 1100rpm), the revs begin to hunt up and down to about 700rpm then back up again.

I've spent nearly £200 in two weeks on different parts and had my head buried in a haynes manualI and still have the same problem. It's not major, the car still drives okay apart from less MPG, but there's definitely something wrong. Even when crouching by the exhaust for a listen on warm idle every 10 to 20 seconds the car coughs and splutters.

Tomorrow I'm going to search for any leaks around the manifold with some carb cleaner. I've very recently had £600 worth of work done to the car including Cambelt, waterpump, all auxillary belts, coolant and brakefluid change and complete break overhaul. The issue seems to have started from then however when I took it back they did an emmisions test which came back fine. I took the plugs out (which are 300 miles old) and noticed the top electrode was very white rather than silver or just dirty, wondered if the car was running lean.

 

That's my rant over, sure it will give someone something to read for a bit😁

IMG_20190429_203212.jpg

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8 hours ago, GLM said:

The issue seems to have started from then however when I took it back they did an emmisions test which came back fine. I took the plugs out (which are 300 miles old) and noticed the top electrode was very white rather than silver or just dirty, wondered if the car was running lean.

I guess you have also checked the more obvious stuff like plugs & coil pack. Though it seems too constant for it to be that.

Air leaks into the engine can cause it to run lean, though it will try to compensate by adjusting the fuel trims, and this can be checked by a diagnostic aid like Forscan that can read the trims. Spraying easy start or even butane (carefully!) around likely leak areas might show a leak by engine note change as it gets the extra fuel.

I think my next stage would be to look at the O2 sensor signals. This may need a scope, I am not sure if the on-board diagnostics can sample fast enough. The upstream O2 sensor should be cycling at a rate of about once per second, between rich and lean. It does this so the cat can reduce NOx (while rich) and oxidise CO & HC (while lean). Spare oxygen is stored in the cat during the lean part, so it can carry on oxidising CO & HC during the rich part of the cycle.

The MoT emissions test only looks for CO & HC, they do not seem to have a NOx test, so a lean engine would be likely to pass, unless the engine management detected the error and put on the MIL.

There is, in the diagnostics, also a closed loop flag. When very cold, or under odd conditions, this cycling will stop, and the fuel mixture is managed in open loop mode (guess-timates really). When the engine settles, it is supposed to go into closed loop mode where the fuel mixture is tightly controlled by the signals from the O2 sensors. This can also usually be read by a diagnostic system to see if the engine is managing to get in to, and stay in, closed loop mode.

 

 

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16 hours ago, Tdci-Peter said:

I guess you have also checked the more obvious stuff like plugs & coil pack. Though it seems too constant for it to be that.

 

New HT leads went on today, coil pack seems fine and honestly after 64000 miles ide like to think it was okay. If I continue to keep changing perfectly working parts I feel like I'm going to cause another issue, but at the same time I don't want to admit defeat to a 1.25 fiesta😑.

I'm afraid most of the info you provided there is a bit above me. I wish there was someone with your expertise around the corner as i think if I was to go into my local dealer and ask them to reset the pcm settings etc they would probably have a giggle and charge me £200. 

Not really sure what direction to turn to next. The whole idea of plug in diagnostics etc does seem interesting as Ive worked in the IT industry however I don't think I've got the time.

I've just had a thought... The garage did all the work to my car and when I collected it they informed me about the common split pcv hose under the manifold, however prior the work being done but still the with split pcv hose, the car idled like a dream, couldn't even tell it was running sometimes, when I collected the car after timing belt etc etc it idled rough, bogs down when you blip the throttle or when reversing out of my steep driveway (still does this), they told me these symptoms were because of the split pcv hose that the car already had when it went to the garage, they replaced this for free for me only charging me for the part, and it made absolutely no difference. 

I've basically back tracked all the work they did replacing part after part and still got no where, I cannot wait to find the cause of this, think I'm going to take a few days away from the situation and have a re-think, it's winding me up.

Thanks ever so much for your help mate, I'll keep you posted when I sort it!

 

George

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On 5/4/2019 at 2:23 AM, GLM said:

including Cambelt, waterpump, all auxillary belts, coolant and brakefluid change and complete break overhaul. The issue seems to have started from then

 

17 hours ago, GLM said:

when I collected the car after timing belt etc etc it idled rough, bogs down when you blip the throttle or when reversing out of my steep driveway

So if I read this right, the PCV hose was replaced after the symptoms appeared, and those symptoms appeared directly after a cam belt change.

Just an idea, but I suspect that a valve timing error, maybe just one tooth out on a cambelt, could have a similar effect. Of the work listed above, only the cambelt could have had such an effect. Checking the valve timing on an engine is a real pain, but it might be worthwhile if all other main suspects, like air leaks, are ruled out.

I am not sure how the 1.25 engine is built, but on some engines the inlet manifold is combined with the cam cover, and must be removed to change cambelts. So an air leak could also have been created at the same time. That is also worth looking at, I would say.

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On my engine the intake manifold doesn't need to be touched, only the alternator removed and a few other bits moved out the way like coolant bottle, changed the plugs today just in case and made no difference, when I took the vacum hose off from manifold to pcv valve the engine revved really high and when I stuck my thumb on the end of the hose the engine would nearly stall unless I remove my thumb, I believe this is normal. 

The next thing me and my dad are going to do is follow your recommendation by using forscan. Could you possibly point me In the right direction off what specific OBD cable I need and/or anything else I'll need. 

One other thing I'm curious about is a little thing on the right of the manifold, some sort of valve or sensor. It has a few vacum styled pipes running away from it. When I unplug it it makes 0 difference to how the car runs. Below are some photos or what I'm talking about.

Thanks again for your responses! You're the only reason I haven't given up so far 😁

 

IMG_20190504_183044.jpg

IMG_20190504_183113.jpg

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19 hours ago, GLM said:

Could you possibly point me In the right direction off what specific OBD cable I need and/or anything else I'll need. 

One source for the ELM327 adapter is:

https://tunnelrat-electronics.fwscart.com/

You can also get them from Ebay etc, but the quality of these things is a bit variable, and tunnelrat have been supplying them for some time. If you get the "modified" one, with a switch usually, they can also read the MS-CAN bus, used for body related stuff like airbags & doors. Whichever way, get one claimed to be compatible with Forscan. I theory all should be, but in practice not all are.

Forscan is free download for Windows, or small charge for Apps, see

http://forscan.org/download.html

The Windows version is a bit more powerful. The website gives details.

19 hours ago, GLM said:

I'm curious about is a little thing on the right of the manifold, some sort of valve

Evap canister purge valve. (Fuel system.)

I suppose it is possible that there could be an air leak into the fuel system, causing excess flow through it, but unlikely, especially as unplugging it (de-energised) make no change.

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