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IAVC issue? - 1.4SS

Mark Adderley

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Hi Blatchatters


Can anyone shed any info on this issue: - when I rev the engine and then take my foot off the accelerator, the revs drop but then seem to hover for about 3-5 secs at around 1800rpm. After that they drop to around 1000 (normal idle) and everything is fine.

I've removed the cable and raised the revs from the throttle body, same thing happens, so I assume it's not the cable sticking. Have also resetting the ECU, but problem's still there. Running out of ideas - can anyone offer any advice?

Doesn't seem to make any difference if the engine is warm or cold, btw.



1400 SS - 58k........ and counting!!

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Is this a forward facing alloy Supersport plenum, or the plastic rover one?


If the latter, there'll be a rubber hose about 1"dia, from the throttlebody into the plenum (With an electrical connection where it goes in). With ignition off, remove the connector and pull the pipe off the throttle body end, cover it with your thumb, then get someone to start and rev the engine.


What you're doing is temporarily removing the IACV from the system, so you may need to give it a little throttle to get it going. If the revs fall perfectly, you know its the IACV is at fault.


They're always packing in, I just block the pipes, tape up the redundant connector and crack open the throttle butterfly with the adjustment screw.


If it is the earlier forward facing setup, your idle is likely controlled by a stepper motor working the throttle butterfly. You can do the same with it, disconnect, try and if its better, open throttle butterfly more and leave the idle control disconnected.


You can take the IACV/Motor to bits and try cleaning...but it'll likely only work for a while. Its not really necessary in a sportscar where you shouldn't be abusing it from cold. I'd bypass it, open the butteryfly for a decent idle and enjoy much nicer revving.



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Yep - it's the IAVC! *thumbup* Cheers

And now I'm going to sound a complete numpty - what does the butterfly adjustment screw reside! *redface* So many metal bits under the bonnet! If you can let me know, I'll raise the rpm a little.


Will it make any difference to starting from cold in the morning?


Thanks again.



1400 SS - 58k........ and counting!!

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I've run mine like this for a couple of years, and its never been a problem when cold. You should be able to get a decent idle, but you may need to tweak it a few times to get it right.


If you look near the thing you disconnected, you should see a small plunger thing below a screw. Sorry that is so vague. Its on the opposite side of the throttle body from where the cable attaches. The throttle "spindle" is the bar that runs though the centre of the body, and the butterfly is bolted to it. The cable is at one end of the spindle, and the idle control is at the other.


With the Idle Air Control motor thingy plugged in, it works a plunger type thing up/down (Small ball on top of it if I remember right) which works the spindle, opening/closing the butterfly. The idle screw is above this.


Sorry I haven't got a photo, but I'm sure you'll find it. It'll be the only screw on the throttle spindle, sitting vertical.


All the best,



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