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Hi guys

I posted a few weeks ago about my van revving up and down by itself. Someone suggested that I clean the Idle Air Control Valve (IACV) with carburettor cleaner. I did this but it didn't solve the problem.

Basically what happens is when the IACV is connected the van starts perfectly but then revs up by itself if left to idle. without the IACV connected the van will not start unless it is already warm. If i start the van then unplug the IACV it runs lovely to start with but then begins to rev constantly fast as the van warms up. This results in massive use of petrol and it sounds like I've got my foot constantly on the accelerator.

I have recently had nearly all the breathing and vacuum pipes replaced but the issue is still there. I have looked at IACVs on eBay and found that VW ones run from around £25 - £150. Do I need to get a T4 specific valve or will any VW one do? they look similar but slightly different shapes so this leads my to believe they are not all interchangeable. New ones from VW are about £150 and I'm loathed to spend that much if it's not necessarily just that thats the issue.

I have no knowledge of engines or mechanics when it comes to cars or vans so please explain accordingly :)

Any help would be very gratefully received.

Thanks.
Tom
 

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If i start the van then unplug the IACV it runs lovely to start with but then begins to rev constantly fast as the van warms up.
This sounds like there must be an air leak somewhere or the throttle's not closing properly for the engine to be reving up without the IACV connected. I would try adding some slack to the throttle cable, just in case it's being pulled open for some reason. Otherwise, you're looking for air leaks round the inlet manifold.

I have looked at IACVs on eBay and found that VW ones run from around £25 - £150. Do I need to get a T4 specific valve or will any VW one do? they look similar but slightly different shapes so this leads my to believe they are not all interchangeable. New ones from VW are about £150 and I'm loathed to spend that much if it's not necessarily just that thats the issue.
There are a couple of different designs of IACV that VW used, but anything labelled as from a Golf GTI of the same vintage should work. Part no is show as 1 here, and a new one can be had for £50 or cheaper s/h on ebay.

Good luck in getting it sorted.
 

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This sounds like there must be an air leak somewhere or the throttle's not closing properly for the engine to be reving up without the IACV connected. I would try adding some slack to the throttle cable, just in case it's being pulled open for some reason. Otherwise, you're looking for air leaks round the inlet manifold.
Got to agree with this,try spraying some of the carb cleaner (with engine running) around any and all connections on the intake system ie manifold , induction hoses , vacuum pipes etc basically anything after the air flow meter.
The engine will rev up on the carb cleaner when it finds the leak
 

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Discussion Starter #4
Just wanted to say a big thank you for all your help. When I managed to finally figure out my from my elbow with my engine (I'm not very engine savvy lol) I cleaned the butterfly valve on the manifold (I think) and it now ticks over lovely. Also replaced a rubber connector on the IACV and it's a million times better.

Thanks for all your help T:
 

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Have a similar problem with engine reving up to full throttle. Replaced Idle valve with new one from ebay (same part number) problem did not clear. by blocking the airflow to the valve the revs stay low (Still ticks over quite high). can stall when really cold! we also had to adjust the throttle position as it had been altered by previous owner!

still no joy! :confused:

Luke
 
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