Fast idle

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Fast idle

Post by jabberwocky22 on Mon Oct 23, 2017 8:37 am

Hi Folks,

Looking for some advice. 
I have a 1994 2.5 petrol Vw transporter Autosleeper.

I have started to have issues with the revs getting stuck at 2000rpm. Initially, I could blip the throttle which would send it back to 800rpm but that is not working now. I can still clear the high revs by turning the engine off and on again and it is fine until I blip the throttle again.
I am confident it is not the throttle cable sticking as there is slack when in tick over position. I have replaced the vacuum hoses.
Anyone had a similar experience?

Appreciate any advice.

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Re: Fast idle

Post by bikeralw on Mon Oct 23, 2017 9:53 am

It would seem that something is stopping the butterfly valve hitting it's stop, the cable will still have slack. If there's nothing obvious on the outside, I'd try taking the air filter off and spraying one of the carb cleaner products down the air intake. Petrol these days contains ethanol, which can gum up things like this if they're not used regularly, I have the same problems with my carb fitted bikes. I think modern fuel is designed to be run with sealed injection systems.
Al.
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Re: Fast idle

Post by jabberwocky22 on Mon Oct 23, 2017 3:30 pm

Hi Al,

Yes that seems reasonable, I will give it a go. 

Many thanks

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Re: Fast idle

Post by jabberwocky22 on Fri Oct 27, 2017 2:36 pm

Right update.
Dismantled and cleaned throttle body, replaced all vacuum hoses, replaced temperature sensor and wiring to sensor. 
I still have fast idle 2000rpm. It is fine when cold. When warm back up to 2000, I have removed the accelerator cable to illiminate that.
You can blip the throttlè and the revs drop but then instantly rise again.
Anyone got any suggestions what might be causing this.
Thanks

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Re: Fast idle

Post by -mojo- on Fri Oct 27, 2017 3:27 pm

If you haven't already done so, I would recommend you ask (and search the older threads) on the UK VWT4forum, because there are a lot more T4 owners there than there are here!

If it's like the T5, there are a number of different things that can cause high idle - for example low engine battery voltage - and they will probably have seen all of the likely causes before.
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Re: Fast idle

Post by jabberwocky22 on Sat Oct 28, 2017 9:27 pm

Thanks Mojo I will give that a try.

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