Cleaning/Replacing the ISCV

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Cleaning/Replacing the ISCV Empty Cleaning/Replacing the ISCV

Post by Davespages on Mon Feb 11, 2008 7:09 am


If you find you have a rough idle and the engine cutting out when engaging the clutch - This is obviously quite dangerous when you are approaching a junction, as you loose your steering and brakes.
Or (in my case) a high idle at 1,300rpm+ then the first thing i would suggest is to RESET YOUR ECU Click here for a guide on how to reset your ECU.

If this does not solve your problem (as with me it didn't) then the ISCV may be to blame and if so its time to give your ISCV a good clean out.

To test if the ISCV is functional you will need a multimeter and will need to locate the ISCV connector plug.
This can be done from above the engine. However, if your Throttle Body Intake pipe routes like mine in the picture below (Zetec SE) you will need to remove it for access.

Cleaning/Replacing the ISCV Iscvcheck1

If it routes directly over the rocker cover (Earlier Zetec) then you may not need to remove it.

To remove the piping:

Simply unclip the pipe from your air box via the clips, then unplug the MAF sensor plug. Next, take a flat screw driver and loosen the Large jubilee clip that secures the plastic inlet pipe to your throttle body.
Once loose, the whole pipe should pull clear enough to see the ISCV plug and it should look like this...

Cleaning/Replacing the ISCV Iscvcheck2

Looking from the passenger side, you can see the ISCV connector plug
Cleaning/Replacing the ISCV Iscvcheck3

Close view...

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Unclip this plug and use the multimeter testing probes RED probe into the clip for Brown and Black to a good earth

If you removed your inlet piping then you are going to need to put it back on, just slide the pipe back over the throttle body and just slide the pipe into the air filter and clip the MAF plug back in.

First and foremost... if the ISCV is fully functional, just by unplugging it with the engine running will make the revs drop to about 600rpm and it may stall, thats good as its working!
Then start the engine up and test for a voltage, you should see a positive voltage on the brown wire (While mine varied) I'm led to believe you should be looking at about 5 volts... Switch the engine off.

If there is NO difference in the rpm then the ISCV needs cleaning, renewing or you may not have that input voltage on the brown wire.
If there is no input voltage on the brown wire i suggest checking fuses and consulting a good garage who are good with electric diagnotics.

Note: Before proceeding make sure that the pins in the ISCV connector are moved back together so they nearly touch. As we pushed the multimeter probes into these earlier, i found they didn't contact propperly afterwards and and idled too low because of this.

Now that we have found whether the ISCV functions or not we can decide what action to take.

(Even tho my ISCV showed some signs of functionality, its good to clean it out so i proceeded to remove it)

If your going to fix it yourself (and I'm assuming you are as you wont be reading this otherwise) then you have 3 options to consider regarding the ISCV.

1) Buy a brand new one from ford or a ford parts dealer (ford call this an Air Bypass Valve) and an average price you'd expect to pay is about 65.00

2) Go to scrap yard before hand and remove one from a scrapper (I was quoted 10 for one so use that as a guide) Then clean the scrapper one, swap them over and then clean your original one and maybe EBAY it.

3) Just remove yours and clean it and put it back on.

I will talk about how to clean the ISCV later in this tutorial.

You will need an ISCV Gasket approx 1.50 depending on the condition of the gasket present (mine was in good condition so didn't need replacing but if in doubt, its only 1.50 so replace it!)

The ISCV is located on the engine side of the Inlet "Manifold" Directly next to the starter motor (behind the engine)
Its only just viewable from the top with the inlet piping off.

Cleaning/Replacing the ISCV Iscvcheck5

(In the above photo i have removed the injector connector plugs for clarity, you DO NOT need to remove these as there is virtually no way it can be removed from above, i'm merely showing you where it is)

Right, as it needs to be removed from under the car, your going to need a pit or a set of ramps or at the very least a jack - then some blocks (to secure the car)

Once the car is lifted and secured, you are going to need a flat screwdriver (just in case it needs help to come off) and a small rachet with an 8mm socket.

Firstly, remove that connector plug we tested earlier.

Below is a picture of an ISCV.

Cleaning/Replacing the ISCV Iscvcheck6

It may not be as easily identified on your engine due to shape (theres variations on early/late zetecs) and whether it plastered in oil etc...

You need to position yourself directly under the exhaust - by the cat (or where the cat should be) I found the best position was with my legs towards the rear of the car and that gave me a good view of the rear of the engine.

You should have this sort of view...

Cleaning/Replacing the ISCV Iscvcheck7

The black "pipe" is the bottom of the inlet "manifold" and just above that, the shinny silvery object is the ISCV.

If you move your head over towards the drivers side then look up at it, you will see it better...

Cleaning/Replacing the ISCV Iscvcheck8

You can clearly see the ISCV in this photo, just behind the Starter motor to the far right.

You should be able to see one bolt, the other is directly on the other side of the ISCV - Upwards and you should be able to feel where it is.

Undo these with the 8mm socket and then carefully remove the ISCV, if it doesn't want to come off when the bolts are removed, use the flat screwdriver to help lever it off.... CAREFULLY!

Make sure the gasket has been removed too - if it breaks then you must replace it.

Once off, you will be confronted with this...

Cleaning/Replacing the ISCV Iscvcheck9

Now its time to clean it.

Ideally you should use Carb/Choke cleaner (even the '151' Brand of carb/choke cleaner available from pound shops will do) however i didn't have any and i used WD40.

Simply spray in through the holes and blast out the crappy oily sludge and debris from the ISCV's internals.

Cleaning/Replacing the ISCV Iscvcheck10

Then tilt it up so that you can spray inside the holes and fill the ISCV up with cleaner, then leave this for a while, (beware - after a while this will evapourate - dont let it, empty the cleaner before this happens)

Then rinse with more carb/choke cleaner.
Keep at it untill all the muck around the spring, centre pin and plastic valve has been removed - i found that mild aggitation of the spring with a small flat screwdriver helped the muck come out.

Rinse again.

Then soak the the insides with WD40 (or any maintainence spray) and leave soak again, then rinse. In all i spent about half an hour cleaning, to remove all the muck and debris.

Let the ISCV drip dry and then it should be sinny inside and out...

Cleaning/Replacing the ISCV Iscvcheck11

Refitting is a little more difficult, but its best to put both bolts into thier holes on the ISCV, Then place the gasket on the ISCV.

Then manouvre yourself back under the car, and guide the bolts back into thier holes, do them up loosely with your fingers, i found the top one easier to do first, then the bottom > Finger tight... then tighted with an 8mm Socket and rachet.
If you have a mini torque wrench, the bolt torque setting is 6Nm or 4lbs/ft

Once this is tight, reconnect the ISCV connector clip, re-fasten the Throttle body inlet pipe (jubilee clip) Slide the inlet pipe back into the air cleaner - fasten up the clips and plug in the MAF sensor plug.

Make sure your tools are all clear, lower the car to the ground (if raised) and try her out...

I found idle to be erratic for a minute or two, then after a couple of minutes a very quick blat on the throttle... she then settled at a happy 800/900 rpm.

After a long drive, the HIGH idle i previously experienced at traffic lights etc has gone.

This solved my problem, However - if you are still having problems, it might be worth turning your attention to the Lambda Sensor.

Well thats it, i managed it so if you know what an 8mm socket is, a rachet and are not affraid of oil or tight spaces (as there little room for your hands behind the engine) i'm 100% certain that you can do this.

If you ever need help, ask the forum regulars or send me a PM - i'm more than happy to help.


Cleaning/Replacing the ISCV Sig
Escort Gti
2.0 16v 153bhp, 141ft.lbs
Davespages 2002-2007

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Join date : 2007-12-09

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