Silly Question Alert

My IAC is starting the usual erratic idling and i couldn’t be bothered sorting it out and am thinking about removing it. The manual reccomends removing it for track use anyway. What effect does removing it have on the idling, silly question part, will it still idle, not idle at all, or be erratic.


It’s not silly, actually it’s debatable.
I just went trough the same question while rebuilding my car and decided to keep it.

It will affect idle, and if you are in varied conditions and your car is used on the road, idle is important.
On track it will just be more difficult to start but after a few secs, temp would be normal and idle would be as set, with the min. screw and the only balancing screw (that balances the left pair Vs the right pair, not individually).
As I intend to use the car in Scotland, cold starting capability is a must, so I asked Dave Walker for his opinion.
He recommended keeping it. He sees no issue with it and it does its job.

Now, if you had Jenveys you can balance very well the TB’s, so maybe I would be more inclined to take it off.
But with the std TB’s I’d say keep it.


Thanks Uldis,

If it makes cold starting more difficult i think i would rather leave it on, as the battery drain does not help the starting situation at this point. Would trying it out be as simple as just removing the valve and joing the pipe where it was ? that way if it was not satisfactory i could put it back easily.

Nope, don’t join the pipes, as this would leave a completely open circuit making it idle either at very high revs or not even start at all (too much air delivered directly behind the butterflies).

If you just want to try it out without either disconnect the electrical connector (hoping the valve is closed at the moment) or disconnect either of its hoses but plug the ends with something (a cork and zip tie or similar)
But beware of very high exhaust temps on one side or the other (if you had a laser temp sensor better) as an improperly balanced pair could lead to lean mixture, whixh would lead to high exhaust temps.
This happened already to Mike Lane, from this board. In that case you’ll have to buy a vaccuum balancer and balance. (you’ll have to dig that posting from the archives)

The bracket holding my IACV went AWOL not so long ago and idling was all over the place, and engine reved when I braked. Garage cleaned some muck out of the valve and fitted a new bracket - now no problem.

Mine got covered in muck, stopped working properly, and it caused stalling coming back in to the pits on trackdays.