Petrol 1.8T Failing to Idle

[planenut]

Originally Posted by TomRS

I'd have it down to the IACV 100% if it runs perfectly fine barring that it can only be Throttle body (but then it wouldnt rev or drive) or the idle control valve...
This sucks small amounts of air into the intake chamber to idle the vehicle its air flow is varied by the water temperature thus increasing or decreasing idle speed as the car warms up.
The reason it stalls when you let off the gas is the Throttle body butterfly shuts closed and where the IACV should take over its failing to do that hence the stall as your just cutting off the engines air supply and without that it'll just cut out.
I'd find a new valve or borrow one to try, but i'd have my money on that.. really not much else it can be.

Many thanks again Tom.

I cannot borrow one, so it seems the easiest, but not the cheapest, is to buy one to test it. Will have another look in between the showers tomorrow.

[TomRS]

Originally Posted by planenut

Many thanks again Tom.

I cannot borrow one, so it seems the easiest, but not the cheapest, is to buy one to test it. Will have another look in between the showers tomorrow.

I have one on a 1.8T engine laying around in my unit... i've earmarked the motor for a ZS at some point when i get some time to find a shell.
I would of course need it back at some point (no rush).. but your more than welcome to "borrow" it to rule out your problems or to such a time that you find a replacement or that i need mine back?
Only thing is i cant post it till Friday as i work away from home Monday-Friday.

[MDMH757]

"there is a wave type effect on the revs, i.e. raises and resumes about every three seconds."

Hi

I had similar symptoms a few months ago, I concur that this could be the iac valve..... changed mine for a 2nd hand one.... all works fine now!!! No fluctuating revs on idle

Maurice


Sent from my SM-G920F using Tapatalk

[planenut]

Originally Posted by TomRS

I have one on a 1.8T engine laying around in my unit... i've earmarked the motor for a ZS at some point when i get some time to find a shell.
I would of course need it back at some point (no rush).. but your more than welcome to "borrow" it to rule out your problems or to such a time that you find a replacement or that i need mine back?
Only thing is i cant post it till Friday as i work away from home Monday-Friday.

Many thanks for the offer Tom, but cancel that -

I took off the air filter pipe and lodged the butterfly open by a fraction, and the engine started each of the three times that I tried it.

I will assume from that that the valve is faulty and will obtain one.

Thank you all for your suggestions, I will return with an update.

[TomRS]

Originally Posted by planenut

Many thanks for the offer Tom, but cancel that -

I took off the air filter pipe and lodged the butterfly open by a fraction, and the engine started each of the three times that I tried it.

I will assume from that that the valve is faulty and will obtain one.

Thank you all for your suggestions, I will return with an update.

Yes by doing that you have basically removed the iacv's entire purpose so as you suggest you need a new one!
Least its a simple fix

[planenut]

Thanks Tom.
Fresh IAV already on way.

[planenut]

Replacement IAV arrived an hour ago - fitted and the engine is idling perfectly again, whoopee!