UK Ford Fiesta Idle Problem ...

Hi all
Have a 1.25 Zetec S Ford Fiesta Ghia on an R plate. A few weeks ago, it started having idle problems. Basically, when it is thoroughly warmed
through - not just warmed up according to the temp gauge - it starts to have issues with being able to maintain idle speed as you approach junctions or roundabouts or get stuck in traffic. Anywhere that you dip the clutch basically. The rev counter drops below 500, and it comes within a gnat's cock of stopping ( it actually did stop once just as I rolled out onto a roundabout ... ). Mostly, it recovers though, and settles back to a pretty even 900 RPM. When it has reached the point where it is doing it, if you leave it idling, it will sometimes start to get very 'lumpy', although the rev counter is dead steady, but slight throttle pressure up to say 1100 RPM, and it's dead smooth again. So far, the garage have tried the air control valve ( ? ) an electrically operated valve that is something to do with idling, apparently, but this did not cure it, so they put the old one back, then last week, they say that they managed to persuade an error code out of the EMU, that indicated a problem with the MAF meter, so they replaced that. Today, I drove into town, and it started doing it again, so I guess it's not that. On the way home, it started doing the opposite, and 'hanging up' at like 1200 RPM when it went to idle. It is going back in again tomorrow, but they seem to be at a bit of a loss. A couple of people have told me that these suffer from bad spots on the throttle position sense pot, which seems reasonable, but I have poked and tapped it, and it doesn't seem sensitive. I have also heard that the setting for the rest position at idle of this pot is critical, but prior to the trouble starting, it had not been touched from factory original setting.
I'd really like to get this sorted, as it's a bit dangerous if it cuts out on a junction. Any thoughts or advice would be much appreciated, or indeed, if anyone has had this problem and knows what it is for sure, please share with me !!
Thanks
Geoff
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The symptoms you describe muddle it a little, but since your car is about 8 years old, I would start with replacing the Throttle position sensor. It should be a non-adjustable type and it's usually an easy task.
The next thing I would do is check ALL the wiring harness ground lugs to the car body... also the engine to frame lead which is separate from the heavy starter cable.
And make sure of the connections from the IAC {idle air control} valve back to the control box
The reason I suspect an electrical problem is that the system should attempt to maintain a minimum idle speed but it also has to figure out WHY the engine rpm is dropping. If the signals are erratic, it has to make a decision on which to ignore and that would make response slow.
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wrote:

Thanks for that. I don't pretend to fully understand fuel injection systems - I'm an electronic service engineer, so well familiar with faultfinding procedures and the problems of intermittent faults - but I do understand them enough to know how they work, basically what all the bits do, and how they hang together to form a closed loop system with the EMU. Many of the electronic items that I work on have similar closed loop servos in them. My feeling was that it was electrical, and that the throttle position sense pot was a possibility. Anyway, thanks for your input. I have printed it off and just dropped the car back in to them, and they were very interested in what you had to say, so we shall see tomorrow ...
Geoff
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It was good information, but your problem is this:-
ISCV
Idle Speed Control Valve
Get it cleaned at a garage (or youself?) with carb-cleaner. Carb deposits build up, and result in the valve being slow to action when you dip the clutch and slow down. A temporary solution would be to keep your foot off the clutch for longer.
Get it to a garage. The sooner the better - the problem may reappear after another 8k miles or so, but give it a go.
Should cost not much at a garage, 15 to 30 max. A new ISCV is also a solution, but geniune ford parts are expensive.
I imagine you've done 45 to 60k in your car already, which is why the problem is suddenly appearing, very common.
http://www.escortevolution.co.uk/howto/view.php?id=7
http://groups.google.co.uk/group/uk.rec.cars.maintenance/browse_thread/thread/949f6cd5121db206/ae611d1221f45858?lnk=st&q=escort+idle+valve+sticking&rnum=2&hl=en#ae611d1221f45858
Watch the google URL wrapping, you will need to copy and paste directly. I had your exact problem, I can assure you 99% that it's the problem :-)
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http://groups.google.co.uk/group/uk.rec.cars.maintenance/browse_thread/thread/949f6cd5121db206/ae611d1221f45858?lnk=st&q=escort+idle+valve+sticking&rnum=2&hl=en#ae611d1221f45858
I'd like to say " Hey thanks !! That's it !! ", but it has been in the garage, and they have both cleaned the IAC valve, and then replaced it, both without success - See Rodan's reply further down, and mine to him. Seems that there may be issues with retraining the EMU after its replacement though, so what you say may yet be valid. Thanks anyway for your input. It's appreciated.
Geoff
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"Arfa Daily" wrote: Ford Fiesta Ghia on an R plate 1.25 Zetec S <UNSPECIFIED YEAR AND MILES>
When thoroughly warmed, idle speed is erratic when approaching junctions, roundabouts or slow traffic. (Basically anywhere that you dip the clutch). The RPM drops below 500, and it almost stalls, then recovers and settles back to a pretty even 900 RPM. If you leave it idling, it can get 'lumpy', although RPMs remain dead steady. Slight throttle pressure up to say 1100 RPM, and it's dead smooth again. The garage replaced the IAC valve but this did not help, so they put the old one back, Weeks later they said the EMU showed an error code of < UNSPECIFIED > so they replaced the MAF sensor.
Today it started doing it again. And later today it started doing the opposite, hanging up at about 1200 RPM instead of going to idle.
I heard that these engines suffer from bad spots on the TPS. but I have but I have poked and tapped it, and it doesn't seem sensitive. I also heard that the setting for the rest position at idle of this pot is critical, but prior to the trouble starting, it had not been touched from factory original setting. Any thoughts or advice? __________________________________________________________
It surely sounds like an IAC problem.
When the IAC valve was replaced, did the garage run the engine through a number of starts, warm-ups, and driving periods to give the EMU time to reset its control parameters? If not, reinstall the new IAC valve and try it again.
I don't know how RPM can be dead steady while idling is lumpy.
Sometimes a good but confused TPS can be retrained by installing a slightly stronger throttle return spring.
Other possible problem causes:
==== Defective EGR valve. ==== Defective Coolant Temp Sensor. ==== Defective garage mechanic.
Good luck.
Rodan.
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Thanks Rodan, more valuable input. Year is '98, miles approx 86k. I too fail to see how engine RPMs can *appear* steady when engine is idling lumpy, but trust me, that was what I saw. I had driven today to nearby town - 8 or 9 miles - and it had been doing the almost stopping routine. I did my banking, and popped in the cake shop and then back to the car - say 10 minutes. It was a bit chilly, so I started the engine, and left it running, whilst I ate my cheese and onion roll ( not relevant, but makes the picture more interesting ... !! ). I had a cup of soup on the top of the dash. Suddenly, the engine started to idle so badly, that the soup cup slid forward on the dash until it touched the 'screen ( car was parked forward pointing down a moderately steep hill - come to think of it, might be a red herring, but on this particular run, the place it starts doing it, is where I first encounter a traffic queue, and it's downhill ... ). At this time, the rev counter was indicating 900 RPM, and it didn't move by as much as a needle thickness during the whole episode. Now that is actually a bit strange in itself, as all the time that this problem has existed, the revs have been able to be seen to be bouncing up and down slightly, which was never the case before I started to have problems. I don't know if the garage did a retrain of the EMU after replacing the IAC valve. I know that it was certainly driven around by the mechanic that fitted it, but I think that he based his conclusion that it was " just the same mate " on the fact that the revs were still hunting up and down a little, and this was the ' ever-present ' symptom of the fault, rather than the almost stopping, which I don't believe that they have ever witnessed. Can they reset the EMU with their magic OBD box, or does it require a full battery off reset to initiate a retrain ? The reason that I ask this is that the radio has not required a recode on each occasion that I have got it back from them, which would suggest tha the battery has not been off ??
Also, interesting that you say about the coolant temp sensor. A friend of mine had exactly this on an auto Range Rover that he owned, and which had an almost identical fault to my little Ford. The EGR valve possibility is interesting too. I wasn't aware of this component, so just did some reading up on it. Quoted faults for it sticking open, sound very like the symptoms that I have. Do all EFI engines have one of these ? I've never noticed anything that looks like the picture I saw, on my engine, but perhaps I've never really been looking.
Anyway, thanks to both for the comments and suggestions so far, and keep 'em coming ... All much appreciated !!
Geoff
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