Engine revs....Rising...

The Joker

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Hi all,
Apologies for a non Merc problem this time, but i'm a bit stuck.

My son's Ford fiesta 1.4 TDCI has an enine rev rise problem.

When accelerating & changing up a gear (say 2nd to 3rd gear at about 2500 Rpm) the engine revs seem to rise by a couple of hundred as soon as you come off the throttle & dip the clutch. The engine itself runs very well, but this is a bit irritating, making smooth changes awkward sometimes. The engine does this in 3rd and 4th too, but not very much in 1st.

Any pointers/advice would be much appreciated.

Thanks...................Joker.
 

Zebra

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I think I've heard of this before.

I wonder if it is perfectly normal in that it is some sort of emission control method, ensuring all the fuel is adequately combusted?

Does it happen if you change up at, say 3k rpm or higher?
 

Number_Cruncher

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Check to see if there's an electrical switch on the clutch pedal, [it's a bit like the clutch equivalent of a brake light switch] and make sure it's working correctly.
 
OP
T

The Joker

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Thanks for your replies,

I can't see a switch on the clutch pedal. It definitely does it at over 3000 rpm. To clarify a little, if the throttle is held steady with the revs at say 3000 rpm, when the clutch is dipped & the throttle pedal lifted , it does not happen. If you accelerate up to 3000 rpm, it does it. Also, if you accelerate to say 3000 rpm in second, and then back off the throttle without dipping the clutch, it certainly happens. It feels like it is "Rolling on".

Weird Eh?

Thanks.................Joker
 

television

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Does it have one of those dual flywheel things as that could cause it
 
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The Joker

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Sorry Malcolm, havent got a clue............
 

Number_Cruncher

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There isn't much that can cause faults like this.

I'm a bit surprised to hear there's no clutch switch - there generally is on the petrol models which can lead to odd idle speed regulation problems - but, I'm not a Ford expert.

Some Fords also have a very odd way of using the throttle position sensor output to define and update the ECU's definition of where "idle" is, and it may be worth plugging the car in, and reading the live data to see what the ECU thinks the throttle pedal is doing.
 


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