I recently bought a 1999 Focus 1.8 Zetec. It has a problem that at first I
took to be the Idle Speed Control Valve, but now I'm not sure at all.
When you take your foot off the accelerator at speed, the engine takes a
long time to lose revs, so there is no immediate engine braking, and also
each gear change is accompanied by a highish revving engine on depressing
the clutch. Often it idles fast, before settling down to proper idle speed.
My Astra had a dodgy ISCV and this Focus behaves almost exactly the same as
far as the fluctuations in idling speed goes, though it never affected the
engine at higher revs the way the Focus does.
With the car at a standstill and revving, I can't recreate this slow to
return to idle problem. (??)
I attempted to remove and clean the ISCV today but found it inaccessible -
couldn't even see it. I also took off the air ducting from the throttle
housing and cleaned the butterfly valve and seats with carb cleaner, which
had LOTS of black oily stuff all over it. I'd like to go back and perhaps
do a more thorough job of this.
Basically I'm wondering what might be the cause of the engine not returning
to idle promptly under load.
58000 miles, full service history up to 54000 miles 3 years ago, so only
done 4k in the last 3 years. Engine otherwise seems fine. Engine
management light is not lit, and the bulb works at ignition on.
Fuel cut off fault perhaps. FI cars should cut the fuel when you lift off
above certain rpm and/or road speed to save emissions and petrol. Sounds
like yours is still pumping fuel in unless the car is stationary. Maybe it's
the road speed sensor at fault but this is not really my area of expertise.
If the intake system is really that badly clagged up then maybe it's
breathing a bit heavy anyway. Do a compression test.
Thats got me thinking - also if the throttle position sensor wasn't showing
zero throttle at lift off, would the ECU still try to inject fuel, and if
so, would the engine continue to rev despite the closed butterfly valve?
Just trying to get a handle on how these systems inter-react.
Yes, and yes, but a stuck TPS will cause a stuck high idle on these. The
programming is also such that immediately you lift off it fully opens the
ISCV which lessens engine braking. It's an emissions thing.
What rpm does it idle at stationary in neutral, clutch up, a/c off? Should
drop to ~650rpm after about 1 second of holding at 900rpm.
Does it warm full up hot- i.e. thermostat? If not then this will make the
idle speed hang, as will a faulty PCV valve (common- under the ex manifold)
Having said all of that, all Foci tend to display what you may initially
find un-usual idling characteristics- it is how they are programmed. Idle
flare on cold start to 2000rpm is normal too, and so is other behaviour the
moment you hit the a/c.
On Ford Focus, this is caused by the Throttle Position Sensor being faulty.
You can clean up the ISCV, which is a good idea as a service job anyway, but
you will still likely have to change the TPS to cure the fault. Once swapped
out, reset your ECU by disconnecting battery or take out appropriate fuse
for a few hours.
On Saturday, 26 September 2009 10:23:50 UTC+1, Davey wrote:
I have the same problem, but a new ISCV was fitted 1000 mines ago and i chanced the TPS for one from a donor engine and still same problem.
It maybe a coincidence that they are both TPS are nakkered, but could it be anything else?
On 26/10/2013 13:38, email@example.com wrote:
First check is that there are no intake air leaks especially the
breather pipe on the back of the manifold, assuming there are none then
the symptoms are very typical of a faulty ISCV. I have tested quite a
few tps sensors and have not yet found a faulty one.
The reason that the iscv is pointed to is because it actually opens when
you are driving along and then shuts itself when the throttle is
released. To quickly ascertain that it is the iscv: disconnect it.
Drive it, you will need to keep it idling by using throttle, so pick
quiet roads/day. If you find that it now behaves correctly during gear
changes then it is the iscv.
On Sat, 26 Oct 2013 13:59:58 +0100, Mrcheerful wrote:
Interesting; both my 1.6 and 1.8 Focuses idle at exactly the same speed
whether the ISCV was connected or not. The only difference it made was
that if you puts lots of idle load on, it slowed a bit. Not enough to
stop it idling however.
I have found both situations, I drove mine for several months
disconnected and had a reasonable idle, it even went through the MoT,
but I have also found ones that have no idle at all, it may depend on
how the throttle plate is set in manufacture. Either way, if the
revving during gear change fault goes with it disconnected then it will
be the iscv.
As an ex Ford master tech I used to see these sorts of problems with mk1&2
Firstly,do you have working and adjusted clutch & brake switches; these can
be kicked out of position and will cause the above symptom. Check these
If the idle rpm's drop by more than ~100rpm or so at a hot idle, electrical
loads and a/c OFF then the throttle body needs cleaning Yes I know the
sticker says dont clean it, but it must be shiny clean. (On a 1.6 check
carefully the PCV system as they are prone to blockages and leaks and on
the 1.8/2.0 just leaks; if the oil filler cap is being sucked on then fix
the PCV system first. There should be just a small amount of vacuum present
at the cap with it working properly.
The PCM doesnt just use the ISCV to control idle, it also adds ignition
advance to help. As someone else said, yes the ISCV is opened during cruise
and decel even when the throttle is CLOSED and fuel cut off- reduces pumping
The TPS must show 0.8v or less with closed throttle, otherwise you will have
issues with idle 'hang and flare' (Ford term) The slots in the TPS can be
filed out to get a low enough voltage if you are having issues, even with a
new genuine ford tps. On the 1.6 there is a modded tps wiring loom and
connector available, but I would expect 99% of cars to be now fitted with
it, as well as the modded CHT sensor wiring.
With the a/c turned on, the PCM uses a different idle / low speed strategy ;
there will be a certain amount of flare and hang at times, this is Normal,
as is some 'mush' (yes another official Ford term) at the lower end of the
I checked for leaks and couldn't find anything,i also swapped the ISCV with two others i have and i still have the same problem, But when i disconnect the ISCV it doesn't happen.
I'm due to sell the car in a weeks time.
any other ideas?
On Thursday, 24 September 2009 22:48:02 UTC+1, Gareth Magennis wrote:
Hi there I recently ctanged the alternator on my Ford Focus saloon. After I
got the engine back together I tried stating it. The idle speed had dropp
ed to around 200rpm and then cut out. I tried moving the car and it runs f
On closer inspection of the engine I noticed a pipe was broken which runs f
rom the fuel intake over the alternator then along the bulkhead to the thro
ttle body. I have replaced this which has improved it some but not cured it
. I have noticed what seems to be another 2 pipe connections at the back of
the throttle body. I don't know what these are or where the pipe if there
is one should go.
When the engine is at idle it will do 1 of 3 things it will rev to low as m
entioned before or it will go to the other extreme and Revs at 3to4000rpm.
Sometimes it will idle at it's normal 1000rpm but it won't be steady the en
gine will hunt.
What could cause this and how do I fix it?
On 16/03/2014 22:21, firstname.lastname@example.org wrote:
commonly it is the breather pipe which is low down on the back of the
inlet manifold, it leads around to underneath the coil pack, it
eventually connects to the engine breather box below the exhaust
manifold. very cheap and often fails.
Motorsforum.com is a website by car enthusiasts for car enthusiasts. It is not affiliated with any of the car or spare part manufacturers or car dealers discussed here.
All logos and trade names are the property of their respective owners.