Could someone help me understand the exact purpose and function of this valve please?

Also, are there any multi meter readings that I may be able to try to both the valve itself and the voltage I should be looking for from the harness side?

The reason I ask is, due to the cold but dry weather of late, I have been out and about in the zed quite a bit. problem is, my tick over starts at 1200 rpm and gradually settles at 750 rpm once she has reached full temp'. This makes initial driving very difficult especially as I have a troublesome gearbox. If I disconnect it, there appears to be no noticeable effect at all.

Surely ( and someone correct me if I'm wrong) if you disconnect it and it doesn't make a difference, that would mean your one is duff.

I'm no expert though so see what others say.

Surely ( and someone correct me if I'm wrong) if you disconnect it and it doesn't make a difference, that would mean your one is duff.

I'm no expert though so see what others say.

 

Pretty much mate. Have a look here; http://s95014253.onlinehome.us/63104/157335.html as it may just need a good clean out. Probably easier to just take it off the back and clean it though.

I've tried cleaning these before with no luck get a second hand one you might need a new paper gasket from nissan. andy z on ebay allways has these that's were I got mine from also dodgy tps or the connector can cause high idle or ecu temp switch or plug

I've tried cleaning these before with no luck get a second hand one you might need a new paper gasket from nissan. andy z on ebay allways has these that's were I got mine from also dodgy tps or the connector can cause high idle or ecu temp switch or plug

 

I tried to clean my first one but it was fubar'd, I'd still recommend trying before going doing the s/h route. Can't hurt. Good point on the other possible causes.

Cheers guys, so far I have removed both items. I have checked the solenoid with 12v and the relevant resistances, all are spot on. I have also dismantled them both and given them a good clean. My issue is with the air regulator valve, the one pictured with the black tubular inlet. The resistance check on this was spot on. Surely I should have voltage on the harness side so as to influence the bi metal strip? at the moment I can not seem to get any voltage what so ever. Hope that makes sense?

If they are the same between n/a and tt's then I have one available that I bought of a fellow member a few months back that I just took off my breaker.

If they are the same between n/a and tt's then I have one available that I bought of a fellow member a few months back that I just took off my breaker.

 

Thanks for the offer mate. At the moment though, I am convinced that I have a harness/connector problem and until I can eliminate that side of things I am a little reluctant to swap the unit.

 

Question, as I understand it, there is a heater element internally. Hense the resistance reading, can I just apply 12v to it so as to activate the bi metal strip? at least that way I will be able to prove the valve one way or another.

 

Also, as this is an aid for initial cold starting. Surely I should see voltage here at start up so as to heat the bi metal strip?

Could someone help me understand the exact purpose and function of this valve please?

 

is this any help...

http://www.pexcom.com.au/z32cms/e107_plugins/content/content.php?content.335

 

and

 

http://www.twinturbo.net/ttnettech/iaa/iaa.html

 

and

 

http://z32.wikispaces.com/Idle+Control

:thumbup1:Thanks for the links Medallion Man.:thumbup1:

Brilliant, can't wait to have a good read up tonight.

Looks like a lot of informative information to get my teeth into.

EUREKA!!!

 

Sussed it.. Overjoyed to say the least.

 

After hours of reading the links, (big thanks Medallion Man, I owe you some rep mate!) and spending some time stripping and cleaning both units, I finally figured out how and what the Air Control Valve is all about. Basically, it's purpose in life is to add a small amount of air during the cold start up process. Depending on the ambient temperature, the unit controls a rotary disc valve so as to control the amount of air required to raise the rpm. So, depending on the outside temperature at the time, the disc valve is open either only slightly or significantly.

The mechanism involved is fundamentally a bi metal spring that's heated at start start up so as to open the disc valve the required amount. Thus increasing the rpm accordingly. Once the engine has reached operating temperature, the voltage to the bi metal heater element is then gradually switched off and the disc valve is fully closed.

 

This is when I had my second eureka moment! Now I know that the above valve was operating correctly,(by the way, I had to adjust the internal disc valve by way of a cam so as to get the correct opening.) and I was now confident the valve was now closed, I then turned my attention to the second AAC valve. This is where the clever bit came to light, I could now set the base idle via data scan. My aim was to set the AAC valve controlled by the ECU to the desired value of 15% (currently mine has been around 25% to 30%)

So with all connectors left in place and data scan displaying the AAC % at 28% I gradually adjusted the base idle screw anticlockwise, bit by bit the % dropped until I arrived at 15% and my tick over settled at 750 rpm.

 

I now have a cold start rpm of around 1200rpm when ambient is at 10 deg' c and a 1000rpm cold start when ambient is at 20 deg' c.

In both cases the rpm dropped gradually within the first five minutes to about 850rpm settling at 750rpm when upto full temp'

 

Chuffed to bits to say the least.

 

Also, as I now have a lower start up rpm and I don't get that un nerving rattle at cold start up!,

Edited April 11, 201312 yr by redwine300

Glad you got it sorted mate, good detective work :detective:

Cheer Steams,

 

I can only hope that it is of some help to others who may have a similar issue.

I'm sure it will :thumbup1:

Good thread...

A bit of an update guys,

 

Part of my Eureka post was incorrect, I will try and explain. I have since discovered that a 14v supply is constantly applied to the heater element of the air control valve, so as to hold the disk valve in the closed position. This takes around 5 minutes and does not relate to the engine temperature needing to be at at full temp.

I have tested the voltage to the control valve both at cold start and at full temp and on both occasions it is around 14v

By the way, I could only find voltage at the connector with the engine running.

 

I think my initial statement as to the tick over settling only when the engine was up to full temperature was due to my connector not making a good contact, and so therefore the only heat available to effect the bi metal spring was from the engine. Hence the rpm taking so long to return to 750rpm

Now that I have cleaned the connector the bi metal strip is now heated via the 14 volts.

 

Sorry for any confusion I may have caused.

 

EUREKA!!!

 

Sussed it.. Overjoyed to say the least.

 

After hours of reading the links, (big thanks Medallion Man, I owe you some rep mate!) and spending some time stripping and cleaning both units, I finally figured out how and what the Air Control Valve is all about. Basically, it's purpose in life is to add a small amount of air during the cold start up process. Depending on the ambient temperature, the unit controls a rotary disk valve so as to control the amount of air required to raise the rpm. So, depending on the outside temperature at the time, the disk valve is open either only slightly or significantly.

The mechanism involved is fundamentally a bi metal spring that's heated at start start up so as to open the disk valve the required amount. Thus increasing the rpm accordingly. Once the engine has reached operating temperature, the voltage to the bi metal heater element is then gradually switched off and the disk valve is fully closed.

 

This is when I had my second eureka moment! Now I know that the above valve was operating correctly,(by the way, I had to adjust the internal disk valve by way of a cam so as to get the correct opening.) and I was now confident the valve was now closed, I then turned my attention to the second AAC valve. This is where the clever bit came to light, I could now set the base idle via data scan. My aim was to set the AAC valve controlled by the ECU to the desired value of 15% (currently mine has been around 25% to 30%)

So with all connectors left in place and data scan displaying the AAC % at 28% I gradually adjusted the base idle screw anticlockwise, bit by bit the % dropped until I arrived at 15% and my tick over settled at 750 rpm.

 

I now have a cold start rpm of around 1200rpm when ambient is at 10 deg' c and a 1000rpm cold start when ambient is at 20 deg' c.

In both cases the rpm dropped gradually within the first five minutes to about 850rpm settling at 750rpm when up to full temp'

 

Chuffed to bits to say the least.

 

Also, as I now have a lower start up rpm and I don't get that un nerving rattle at cold start up!,