Air idle valve

MartinClan · #1 16th March 2009, 07:41

My engine is running a bit fast on tickover. I suspect the air idle valve. Does anybody know anything about these - how they are actuated (pulse up pulse down or ???), cleaning (carb cleaner maybe), testing etc.

Cheers

Robin

GreatOldOne · #2 16th March 2009, 08:38

I cleaned mine with carb cleaner. The valve rotates through 90 degrees if I recall correctly.

When the ignition is on on mine, before I crank, I can just about here the valve rotate open to what I believe is half way. It 'buzzes' slightltly as it holds it open.

That said, I haven't runmy engine for any great length of time so I can't comment on wether it's operating correctly and idling at the right speed.

Have you checked the idle control screw on the top of the throttle body?

MartinClan · #3 16th March 2009, 12:34

Quote:

Originally Posted by GreatOldOne

I cleaned mine with carb cleaner. The valve rotates through 90 degrees if I recall correctly.

When the ignition is on on mine, before I crank, I can just about here the valve rotate open to what I believe is half way. It 'buzzes' slightltly as it holds it open.

That said, I haven't runmy engine for any great length of time so I can't comment on wether it's operating correctly and idling at the right speed.

Have you checked the idle control screw on the top of the throttle body?

Thanks Jason

I think I should try some carb cleaner as a first option. Do you know if it is a digital or analog device? IE is always open or shut or can it also be somewhere in between?

Cheers

Robin

GreatOldOne · #4 16th March 2009, 13:22

I'm pretty sure it's analog - it can be somewhere in between fully open and fully closed; I'm certain that when I was fiddling around with the engine prior to stating it I had the valve off whilst still connected, and that when I turned the ignition on, it flicked to half open.

I'll have a look tonight, and double check my Bently manual when I get in.

MartinClan · #5 16th March 2009, 13:42

Quote:

Originally Posted by GreatOldOne

I'm pretty sure it's analog - it can be somewhere in between fully open and fully closed; I'm certain that when I was fiddling around with the engine prior to stating it I had the valve off whilst still connected, and that when I turned the ignition on, it flicked to half open.

I'll have a look tonight, and double check my Bently manual when I get in.

Thanks Jason

I looked at the Bently Manual but it didn't have much detail (unless I was looking in the wrong place). Since the last post I have at least established that there are two controls - one for open and one for close - but still no closer to finding out if it is analog or digital.

Cheers

Robin

Patrick · #6 16th March 2009, 14:27

I had lots of idle issue on my engine, I've got a list of stuff to check here:

http://www.msportster.co.uk/faq.asp?FAQ=13

Give the ICV a good clean out with carb spray and make sure there are no air leaks. Whatever you don't adjust the throttle stop as that's set from the factory and shouldn't move. It's also worth checking the TPS to make sure its setting the ECU on idle settings

GreatOldOne · #7 16th March 2009, 17:06

Had a look, and it is half way open when the throttle is closed. When power is applied to the valve, it momentarily springs fully open and then back to half way, and buzzes.

All of the info on the ICV and testing it is in Chapter 6. TBH, I didn't do much past blasting it with the carb cleaner to ensure it was clean and could move freely.

The adjuster on top of the throttle body is as Patrick says supposedly set at the factory. Mine didn't have an anti tamper cap on it as the manual states it should have, so I guess someone must have buggered around with it in the past. I set it back as per the instructions in section 6.

peterux · #8 16th March 2009, 21:14

Mine buzzes too.
A sharp tap with the handle of a plastic screwdriver might be enough to get it going if its stuck.
I had one injector stick despite being professionally ultrasonically cleaned and a little tap got it going.

Patrick · #9 16th March 2009, 22:36

Mine buzzes too as soon as you turn the ignition on position 2 I think it uses a square wave to control how far it opens.

MartinClan · #10 17th March 2009, 07:31

According to the famous Brian Moore of the E30 zone it's a balanced armature design. (I'm an electrical engineer and I am no wiser) Anyway - the long and the short of it is that it is analog and the position of the piston depends on the difference between two signal.

Anyway according to the Bentley manual you can test it by quickly turning it in your had and seeing if the piston moves quickly. I think I favour Peters idea of tapping it with a screwdriver and seeing if the idle settles down....

I bought a spare one off ebay yesterday for £14. Seems like a good investment even if I don't need it right now as new ones are £100 +

Robin