Car revs high when changing gear - any advice VERY welcome

[im]

Hi chaps (and chapettes)

I've nipped across from my usual domain on the TVR forum to ask kindly if any of you can help. My 18 year old son has his first car, a 1.3 fiesta LX and he just come home and asked me to nip out in his car with him for a quick spin to let me hear something.

When he depresses the clutch and selects a gear the car Revs high for a couple of seconds before settling down again.

Any comments advice would be highly welcome as I'm no mechanic.

Thanks

[nighthawk]

how old is it?

The fueling system has had a few changes over the years

carb
central fuel injection
sequencial electronic fuel injection.

If it's a late car with SEFI, i'd be looking at 3 possible areas

Vehicle speed sensor
Idle air control valve
corrupt signal from the throttle position switch

The last 2 are known areas and TSB's exist to help eliminate the concern

[im]

nighthawk said:

how old is it?

The fueling system has had a few changes over the years

carb
central fuel injection
sequencial electronic fuel injection.

If it's a late car with SEFI, i'd be looking at 3 possible areas

Vehicle speed sensor
Idle air control valve
corrupt signal from the throttle position switch

The last 2 are known areas and TSB's exist to help eliminate the concern

Its a P reg - does this help? What is a TSB? Thanks so much for the info so far.

[chriz1]

check that the pipe which goes into a little round valve or something on the left hand side of the air filter box hasnt fallen off as this is a vacum pipe and sometimes strangles the idle of the engine sould be clipped onto the box where the clips are to undo the airbox

[im]

chriz1 said:

check that the pipe which goes into a little round valve or something on the left hand side of the air filter box hasnt fallen off as this is a vacum pipe and sometimes strangles the idle of the engine sould be clipped onto the box where the clips are to undo the airbox

Checked this Chriz - everythings OK so still no joy - looks like it might have to be the dealers for me. Damn...

[GravelBen]

If its his first car and he learnt in something different it may be that he's being a bit slow lifting off the throttle as he presses the clutch in. Does it do the same thing with you driving?

Not meaning to sound patronising or anything, but different cars can often have quite different pedal actions and if he doesn't have much experience it would take longer to adjust to it or realise whats happening.

ETA: just re-read the OP and I'd interpreted it as meaning he's just got his first car, but it doesnt actually say that, if its been fine previously and only just started doing this then forget what I suggested.

Edited by GravelBen on Monday 26th February 02:37

[roop]

Sticky throttle...???

[Zad]

In order of likelihood. Sticky idle control valve. Sticky throttle butterfly. Leaking throttle assembly letting in air.

If you blip the throttle with it out of gear, does it still do it? There may be a faulty clutch switch or similar.

[im]

Hi Chaps and thank you so very much.

GravelBen: Not the first car he's driven, but it is HIS first car so his driving is not the problem.

roop: Thats what I initially thought but then it would do it when its out of gear and it doesn't.

Zad: No, if I blip the throttle with it out of gear, it doesn't do it. Does this point to something do you think?

MANY, MANY THANKS GUYS - Very much appreciated.

[RDE]

Is it not just a worn out clutch? Sounds a bit like what I experienced with my Puma - my normal driving style led it to rev more than usual as the clutch found its feet. Have you tried putting it in a low gear and booting it? If the revs rise but the car doesn't accelerate, that's your problem. Or maybe i've just misunderstood the explanation...

[Zad]

I'm sure I have heard of this before, but I can't remember what car it was on (almost certainly another Ford). Search seems to be down again, and the google version isn't very helpful.

It may sound daft, but have you tried removing the throttle cable and dropping some oil down it? Throttle cables can get really stiff over time. It may be that the vehicle senses the road speed and uses the idle control valve to keep revs up to aid gear changes, but the addition of a bit more throttle off load causes it to race a bit.

*Memo to self, check when search comes back*

[Zad]

I checked, and it was no help

www.pistonheads.com/gassing/topic.asp?t=283820&f=129

Looks like it is all down to checking the vacuum pipes for blockages and idle control valve. Bum.

[nighthawk]

Subject/Concern: Engine idle hang up during gear changes
Model: Ka built from 09.1996 (build code TL) and Fiesta built from 08.1995 to 09.2001 (build codes ST to 1C) with 1.3L Endura‐E engine
Markets: All
Section: 303‐14A (23)

Summary
Should a customer express concern about engine idle hang up during gear changes, the probable cause is a corrupt throttle position sensor (TPS) signal due to poor electrical contact at the electrical connector. This concern should be rectified by installing a new TP sensor wiring loom and connector.



and

a service message on similar


FIESTA & KA 1.3 ENDURA - REVS HANG UP ON DECELERATION / POOR DECELERATION FEEL MAY BE CAUSED BY A RESONANCE IN THE IDLE AIR CONTROL (IAC) VALVE CAUSING IT TO STICK. TO OVERCOME THIS A REVISED SPACER BETWEEN MANIFOLD AND IAC IS AVAILABLE.


hope that helps

[im]

Brilliant Nighthawk - thank you very much!