Can a ISCV cause idle revs as high a 2500 rpm??

[JanDK]

Just thinking as I have no leaks (tested with diesel start spray) all volts etc are close to perfect, when using FLUKE at the ecu plug. When unplugging iscv it drops to what ever baseidle is set to and its at the moment about 600 rpm cold (IDLE isnt set properly) Just think the rpm is seriously high perhaps caused by the iscv.

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[cozmeister]

Yes - if it's completely broken it'll go to over 4000 (mine did when it fried).

An air leak at the inlet manifold will also increase revs.

[KSA-Cossie]

Hell yeah it can.

[Kestrel77]

Yup

[JanDK]

hmm.. it says "click" when connecting with ignition on or startet engine.. if startet it gets mad.

So I can be 211% sure that it is not another sensor causing the ecu to tell the iscv to go "high"??


broken... it worked the day before it did this.

What causes it to give up life ??

[martysmartie]

They always cause problems with sticking, normally socking them in petrol over night clears them out, however you are right thinking it may be other problems, as you have said when you unplug it the idle drops, so I would say it may be being told to open this much. Does the speed not drop at all even when hot?

Martin

[cossie daz]

i had my cossie in storage and only drove it once a month if i was lucky and used to tick over at 3000rpm for first few miles then would drop

[tabetha]

It could admit enough air to redline the engine with no load on it, just do the spraying etc then wop 12V into it from a battery, this frees them up nicely.
If this doesn't work you know it's a sensor telling it to do the revs.
tabetha

[JanDK]

Originally Posted by martysmartie

They always cause problems with sticking, normally socking them in petrol over night clears them out, however you are right thinking it may be other problems, as you have said when you unplug it the idle drops, so I would say it may be being told to open this much. Does the speed not drop at all even when hot?

Martin

Nope

By the way, the iscv is relatively new, and I do know it dosnt make it last forever (new parts do break to) but I did give it a clean a few days before, and it work for one drive.

[JanDK]

Originally Posted by tabetha

It could admit enough air to redline the engine with no load on it, just do the spraying etc then wop 12V into it from a battery, this frees them up nicely.
If this doesn't work you know it's a sensor telling it to do the revs.
tabetha

I agree with you.. so far I see logic... but following guides found here an dthere on passionford and THE WORKSHOP MANUAL, everything has the correct value.

One thing though... I have tried 2 extra tps I have, and all give the same value. I cant get them to give me LESS than .38v (my papers says .6V with closed throttlebody) I remember it is .5V at the moment. And properly most important.. I dosnt make fuelcut when letting go of the throttle, and thats is NOT right, so at the moment I am sourcing a factory new tps and changing it on suspicion.

It is not the first time I have doubt about the tps being faulty and not showing it when testing. I also remember something about the tps being a kind of in direct connection (via ecu ofcause) with the iscv, have you heard of this???

[RS500/364]

took mine apart and unsonic cleaned erm same as my injector
worth getting the cheap unltrasonice as the new icv can cost Ł92

[JanDK]

Originally Posted by RS500/364

took mine apart and unsonic cleaned erm same as my injector
worth getting the cheap unltrasonice as the new icv can cost Ł92

Exactly why I clenaed mine.. thay expensive pieces. But it isnt the iscv playing with me.. its something ells. Most likely the tps....

[YBJ]

Had this problem when my TPS was set at a wrong value. When setting it at 0.35V or higer it would rise the idle speed up over 2000 RPM. After setting it at 0.30V everything was fine.

[Glenn.]

I had a fault on my cossie,when i used to drive it from cold it felt like the choke was sticking on and the car used to drive on its own when i took my foot of the throttle.I got told to take the ISCV out and lub it up with brake fluid.It has worked a treat.Its stopped doing the fault and the revs also dont go up and down from cold either.

[JanDK]

I tried setting my tps several times these days.. .4v .35v .3v .. tomorrow to let the spring in the tps set it, and give it a go.

[ybturbo]

Yes the ISCV is capable to rev the car to 2500rpm and also the TPS issue is a possible cause so the ISCV receives wrong signal from the ECU...

[JanDK]

fixed!! I set the tps to 170mV as the tps-spring trick didnt fix it. It had instantly normal idle and it fuelcuts when letting of the foot, and that must mean the ecu get it requiered idlesignal.

[Glenn.]

Nice one mate glad you sorted it.

[JanDK]

Thank you

[puntogtkid]

my idle is at roughly 1700 Rpm at all times, hot cold etc... what is the correct idle speed, mine is a stage 3 set up..
Ste

[cozmeister]

Originally Posted by puntogtkid

my idle is at roughly 1700 Rpm at all times, hot cold etc... what is the correct idle speed, mine is a stage 3 set up..
Ste

850rpm for L6 ECUs, and 900 for L8 ECUs - check which you have got first.

Disconnect your ISCV and see if the idle drops - should drop to more-or-less the correct idle speed. If it drops, then your ISCV is either gunged up and stuck open or broken. If it stays high, then you might have a leak somewhere on the inlet side, maybe a blown inlet manifold, plenum or throttle body gasket, or slightly more likely, a split or loose-fitting hose on the inlet side.

[rudeboy]

Instead of starting a new thread I'll ask here ...

My three door is starting to have idle (and starting) issues ... but only when warm.

When warm the idle is either smooth but at 1500 rpm, or irregular / rough at 1000 rpm.

Also starting the car when warm it seems to be taking a while to get fuel (just ticks over) I counter this but letting the system prime from the fuel pump before firing.

Cold start is fine.

I dont think the erratic idle is caused by an airleak because it goes from high to low (not constantly high) I'm thinking a sensor ... I'll disconnect the ISCV and see, until then anyone experienced similar ?

[tabetha]

If you haven't in a few years changed the CTS do so now, as it's so important, then set co to what it should be for the chip you are using ?
Disconnect the iscv, and set base idle to around 900 rpm, with all electrics off, engine apart and FULLY warmed up.
tabetha

[BigErn]

Originally Posted by cozmeister

Yes - if it's completely broken it'll go to over 4000 (mine did when it fried).

Mine hits 5000 with it plugged in, it happened on the motorway, was like cruise control. Shat meself when i dipped the clutch at slip road

[rudeboy]

Thanks (again ) Tabetha ...

... I'll give it a go ... and let all know.

and yeah all 20 y/o shonky sensors still installed!

[Pri007]

Guys looks like i've got the same issue.

When i disconnect the ISCV the revs drop to normal level.

Quick question though, what sort of damage would be caused if i were to drive with the iscv disconnected?

[martysmartie]

^^ Posted on your other thread.

Martin

[cozmeister]

Originally Posted by BigErn

Mine hits 5000 with it plugged in, it happened on the motorway, was like cruise control. Shat meself when i dipped the clutch at slip road

A knackered PF01 TPS will also cause it on an L6 or L1 ECU.

If the PF01 TPS is broken, and sending a low voltage to the ECU even though the throttle's closed, the ECU will assume you've planted your foot on the throttle because the PF01 output drops as the throttle opens. If your Idle control valve is also stuck open, maybe because it's gummed up or because of an electrical fault, there'll be enough air flowing through for the revs to rise that high.