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PeterJeeves507
Hi all,

My dad has a 2004 54 plate mondeo, mk3 I think, with the 1.8 duratec petrol.
It has developed a fault recently whereby when coasting along it idles at 1300 rpm, but when the car comes to a complete standstill the idle drops to normal,
My fiesta does a similar thing but it has always dobe this, while the mindeo hasn't,

Does anyone have any ideas as to what may be causing this?


Cheers,


Peter
FOCA

Its probably just the ECU adjusting the revs (to get a smoother gearchange/ to prevent stalling etc)

PeterJeeves507
That's what I have suspected all along, but dad insists that theres something amiss. He read somewhere that theres a pipe thats split going from the inlet manifold to somewhere oil related, possibly a breather pipe, which causes it, its apparently a common fault on duratec and zetec engines, so should probably check my fiesta too!
FOCA

That's what I have suspected all along, but dad insists that theres something amiss. He read somewhere that theres a pipe thats split going from the inlet manifold to somewhere oil related, possibly a breather pipe, which causes it, its apparently a common fault on duratec and zetec engines, so should probably check my fiesta too!

Yes, there is a pipe from the crankcase breather/ PCV (positive crankcase ventilation) valve to the air intake, if it splits it could cause the symptoms you are describing (because it may draw extra air)- so worth checking (especially if it did not do it before) - the ECU also adjusts the tickover too, especially during warm-up - Another thing worth checking is the idle control valve, which can stick   

adi v6

I no on my mondeo the eba vacuum pipe was the fault on mine

PeterJeeves507
Sweet as, cheers! I'll see how the fiesta gets on, as far as I know its done it since ive had the car, it was 4 years old when I got it, and it doesn't idle any higher that it did then, while coasting or sat on the drive, I tend to use engine braking anyway as its meant to be more efficient than coasting!
FOCA

Sweet as, cheers! I'll see how the fiesta gets on, as far as I know its done it since ive had the car, it was 4 years old when I got it, and it doesn't idle any higher that it did then, while coasting or sat on the drive, I tend to use engine braking anyway as its meant to be more efficient than coasting!

Yes i saw that on top gear - if you "coast" in gear the ECU cuts the fuelling but if you "coast in neutral" it uses a little fuel to stop it stalling/ keep the engine running    

PeterJeeves507
I was told the story of a chap in an audi who was driving down a mountain road in europe somewhere, and didnt use the throttle for quite a few miles as he was going down hill, went to use the brakes and got very little servo assistance as the engine had essentially gone to sleep, havent had the chance to back to back coasting vs engine braking, itll be interesting to see which is more efficient! If its true that modern engines use no fuel at all when slowing down then engine braking it is! My engine theory knowledge comes largely from working with race engines, and we arent usually bothered by fuel economy on the track!
stooge75

engine braking's one o the worst things for your clutch though

jeebowhite

agree with Angus, its not healthy. The servo should be alive for as long as the engine is ticking over though, just because it cuts the fuel to minimal being injected shouldn't stop the engine in essence running...

djtonymc

Modeo 1.8 lx petrol 
keeps cutting out when turning steering
at first on start up idol goes up and down then it cut out then start up again revs die and give it lots of revs keeps running 
put it in garage they put a diagnostics on p1018
replaced map sensor
had a full service 
oil change
all filters changed 
spark plugs - coil pack - new leads 
idle valve  

no leaks or splits in any pipes 

mick85
Sound like intake manifold control runner it vacuum operated when u clutch to change gear does the revs hold over thousand then drop off slowly when u switch u car off can u hear any hissing sounds


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