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Engine revs going up & down
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Freestyler
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Joined: 31 Jan 2010
Posts: 13
Location: Trieste, Italy

1993 Ford Fiesta

PostPosted: Wed Feb 03, 2010 6:52 pm    Post subject: Engine revs going up & down Reply with quote

It's an old problem of my Fiesta... I did a search but didn't find anything interesting about this issue.

Sometimes my engine accelerates alone:

a) when idle constantly cycles from usually 2000 to 3000 rpms or

b) when I'm not pressing the gas pedal it's constantly at 1500-2000 rpms, both while idle or while driving

And various combinations of the problems above Very Happy It seems to me that this problem is usually more present when it's cold, so in fall and winter.

My mechanic says that it's a problem of the (sorry, I don't know it's exact name in english, in italian is called "electronic switchbox", the "brains" of the car) and that to resolve this would be necessary to change it, but the car is old so it isn't worth doing this. I was hoping that the problem could be more easy to solve, so I'm here Smile

Any clues? Smile
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iesta_08
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Joined: 18 May 2008
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Location: Stoke-On-Trent

1995 Ford Fiesta Classic Quartz

PostPosted: Wed Feb 03, 2010 8:21 pm    Post subject: Reply with quote

i fi understand what you saying

i presume you are saying that basically your engine is idleing high

unfortunately, not alot you can do to get a round it, what i would suggest is to:

re aligh tappets
re-place rocker cover gasket
replace air filter
clean airbox

or if you got the knowledge and the confidence you can adjust the idleing valve (thats if its a injection engine not carb)
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Freestyler
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Joined: 31 Jan 2010
Posts: 13
Location: Trieste, Italy

1993 Ford Fiesta

PostPosted: Wed Feb 03, 2010 8:30 pm    Post subject: Reply with quote

iesta_08 wrote:
i presume you are saying that basically your engine is idleing high

This is one of the issues. The second is that sometimes the engine, when I'm not touching anything, keeps going between 2000 and 3000 rpms (sometimes higher, sometimes lower), like I was tapping the gas pedal.
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iesta_08
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Joined: 18 May 2008
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Location: Stoke-On-Trent

1995 Ford Fiesta Classic Quartz

PostPosted: Wed Feb 03, 2010 8:32 pm    Post subject: Reply with quote

does it "bounce" .. by which i mean bounce between the 2 levels of revs or does it rev in a single move upto 3K

if its a continuos revving up and down then that will be a vacuum pipe is come off, and when connected you will notice the engine run smooth

does this revving happen when moving? or at standstill?
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Freestyler
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Joined: 31 Jan 2010
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Location: Trieste, Italy

1993 Ford Fiesta

PostPosted: Wed Feb 03, 2010 9:04 pm    Post subject: Reply with quote

Yes, the revving is continuous. Sometimes it stops after a few times, sometimes it continues on and on. It happen when I'm not moving, or when I'm moving and the clutch pedal is pressed (basically when I'm changing gear).
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AndyMk3
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PostPosted: Wed Feb 03, 2010 9:08 pm    Post subject: Reply with quote

check ur idle control valve
mine did this
had to change my idle control valve and tps - throttle positioning sensor

its like it trs to drive it sels its very irritating haha. mine used to just rev up and down and up and down.
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iesta_08
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Location: Stoke-On-Trent

1995 Ford Fiesta Classic Quartz

PostPosted: Wed Feb 03, 2010 9:10 pm    Post subject: Reply with quote

sounds like a vacuum pipe to me, happend to me before when i was sat at traffic lights, my engine would rev up and then rev down and up and down over and over, in neutral

i would check your hoses located around the inlet manifold, stand infront of your bonnet and look down the left hand side of airbox and you should see a T shaped plastic piece which will have 3 rubber pipes connected in the T shape...

firstly make sure these are securely fastend, and then the pipe that runs to the engine (left of the T piece) make sure that is over the hole on the inlet manifold..

have you got a rev counter fitted? did you fit it yourself or was it factory fitted?
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Freestyler
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1993 Ford Fiesta

PostPosted: Wed Feb 03, 2010 9:21 pm    Post subject: Reply with quote

iesta_08 wrote:
have you got a rev counter fitted? did you fit it yourself or was it factory fitted?
I have it, that's why I'm so sure about the rpms Very Happy As far as I know it was factory fitted, I don't think that my uncle or my grandpa touched anything Smile
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iesta_08
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1995 Ford Fiesta Classic Quartz

PostPosted: Wed Feb 03, 2010 9:29 pm    Post subject: Reply with quote

ok cool, i only asked as if it was wired in it could of had some interference,
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Freestyler
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PostPosted: Wed Feb 03, 2010 9:37 pm    Post subject: Reply with quote

Thank you everybody Smile

When I'll have some time I'll check my dear Fiesta Cool
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3lward
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Joined: 04 Mar 2009
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PostPosted: Thu Feb 04, 2010 12:14 am    Post subject: Reply with quote

probably your idle control valve, its a old car mind things het clogged up just lash it with carb cleaner or something and also spray a bit of carb cleaner down the actual carburettor, did that mines never done it since Smile
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trecoll
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1997 Ford Fiesta LX

PostPosted: Thu Feb 04, 2010 8:49 am    Post subject: Reply with quote

Its not the ICV. The ICV would cause lower revs than that. It will be a vacum hose as said.
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3lward
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PostPosted: Thu Feb 04, 2010 1:14 pm    Post subject: Reply with quote

trecoll wrote:
Its not the ICV. The ICV would cause lower revs than that. It will be a vacum hose as said.


i had exactly the same probably i checked all the hoses wasnt them so lashed the carb and bit around it with carb cleaner and its never done it again
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trecoll
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PostPosted: Thu Feb 04, 2010 1:32 pm    Post subject: Reply with quote

So why say the ISCV then? You said it yourself, it was a problem with your carb....
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3lward
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PostPosted: Thu Feb 04, 2010 2:34 pm    Post subject: Reply with quote

trecoll wrote:
So why say the ISCV then? You said it yourself, it was a problem with your carb....


well whats the thing under the carb then?
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