I cleaned my IAA valve yesterday which made no difference at all. I disconnected it today with the engine running and nothing happened. Should the engine stall when I disconnect it?

If it's broken does anyone know if I can just buy the solenoid?

 

Stu, the engine won't stall when you disconnect the solenoid valve.

 

This normally has to be disconnected when setting the engine idle rpm.

 

Have you checked that the O2 sensors are in working order?

 

Steve

 

Hi Steve, Yes I have checked the O2 sensors and they are fine. I have also run the engine diagnostics on the ECU.

Should the plunger in the IAA valve oscillate up and down when the ignition is on or when the engine is running?

When I come to a junction, slow down and apply the throttle again the revs drop, there is a pause and the car picks up again?

 

Check PCV Valves

 

Stu, I'll investigate the plunger operation with my mechanic as I'm not sure.

 

I think your looking in the right area for your problem because I had a similar thing in my 2.0 16v cavalier. The problem turned out to be the air/idle control valve.

 

Steve

 

The plunger in the AAC valve on the IAA unit is operated

by the ECU with a PWM (Pulse Width Modulated) signal.

By doing this, the ECU is able to gradually adjust its opening.

When you disconnect it, the revs should drop ~50 RPM (that's if the idle screw is adjusted right).

 

Adjust the idle first, then reconnect the AAC valve.

The idle should raise a little when reconnecting the solenoid.

 

Have you cleaned the throttle bodies?

As Anders said the PCV-valves are a hot tip as well.

 

As for the solenoid, you can not buy it separately.

Check its resistance. It should be ~10 Ohm.

You can also apply 12V to it for a short while and see if it clicks.

 

Hope it works out for you.

Check the Tech-section of my home page for additional tips.

 

Maciej

[www.z-car.net]

 

 

Thanks.

I have replaced the PCV valves a few weeks ago.

I will try putting +12V to the solenoid to test it and see if it is working.

Does anyone know how much a new IAA valve is?

Once I have this cured I only have to cure my vibration which has developed due to the rear wheels being 15 deg out of alignment! I get a nsaty vibration thru my seat at about 30mph which clears past 50mph.

Many thanks for all your help guys.

 

From tt.net Tech:

 

AAC Valve Assembly. P/N: 23781-40P10 (~$215 from Courtesy)

AAC Gasket. P/N: 23785-40F00 (~$1 from Courtesy)

 

Maciej

 

Right I have checked the solenoid with +12V and it clicks away merrily.

I have ajusted the TPS to 4.7V and disconnected the IAA valve to set the idle at 750rpm, car runs superb until I reconnect the IAA valve and the revs go upto 1800rpm? disconnect and back to 750rpm, reconnect upto 1800rpm???? HELP!!

 

I've got a bloody hole in my radiator now, someone is punishing me for something!!

 

Until last year I had a TT just like yours...it was like it was cursed.

I was fixing one thing and something else broke down and to put a cherry on top while it finally ran without problems for a few weeks, the timingbelt snapped (at 5000RPM)...oops..

 

Take my advise, sell it while it still runs and buy another one.

 

 

Stu, 4.7v on the TPS ??

 

This is where your problem is.

 

This setting should be .42-.44v at idle.

 

Steve

 

Sorry Steve I meant to write .47V. MacieJ had an article on his site for the settings.

Heres what I did:

Disconnect IAA valve solenoid.

Set TPS to .47V

Set idle to 700rpm

reconnect IAA valve and idle goes upto 1800rpm!

Should I try setting the idle with the IAA connected?

 

Stu,

 

Have you tried resetting the ECU (diconnecting the negative terminal on the battery). Make sure the IAA etc is all connected when the reconnect the battery. I think the battery needs to be disconnected for a good 1/2 hour.

 

Andy

 

as opposed to a bad half hour ? ;)

sorry, couldn't resist...

 

You joke here Craig but I think Stu has had a few 'bad' half hours recently.

 

Stu, I don't think you need to disconnect the IAA when you set the TPS. Set the TPS to .44v and then disconnect the IAA to set the idle at 750rpm (manual Z)

 

Steve

 

Thanks I'll try disconnecting the battery for a while and see if that makes a difference and will check the TPS when I go home at lunch.

 

yeh yeh LOL

 

Craig, How do you justify taking the piss out of the car mats thread and then come out with a joke like that? hehe

 

Wow disconnecting the battery worked, it's now idling merrily at 750rpm.

Thanks guys.

 

Stu, is the low rpm hesitation fixed?

 

Steve

 

Hi chaps

Was reading your thread......on my Jap spec auto TT, the idle speed has over the past year crept down from 750rpm to about 600-650rpm........would disconnecting the battery get it back up to 750 ?

 

Cheers

William

 

The idle-screw sets the minimum idle speed, so resetting the ECU won't help.

The problem could be dirty throttle bodies, allowing less

air to pass when closed (they never close completely).

I would suggest then you clean them first and then adjust the idle-screw

if the idle is still to low.

 

Maciej

 

Sorry......but where can I find the idle screw ?

 

Thanks

 

William

 

Check out the Tech section of my home page for

pics and tips.

 

Maciej

[www.z-car.net]

 

William go to www.z-car.net and select Tech Macie has a breakdown of the process and the valve which will show you where the idle screw is.

If you stand next to the battery and look at the top back corner of the engine nearest the battery you will see the IAA valve attached to the back of the engine with 2 pipes connected to it.

If you look under the pipes on the side you will see the idle screw, you will need a stubby screwdriver to get at it.

turn it clockwise to decrease rpm and anticlockwise to increase.

 

Steve the low rpm hesitation was fixed for a day and is better than it was but when I cleaned the valve last weekend I didn't realise there were two valves I thought the other was a sender and I only cleaned the large solenoid one so I am going to take it apart again and have another go.

It did work fine for a little while though so I'm heading in the right direction.