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Discussion Starter · #1 ·
Hi

Just ordered a new iac valve for my 89 900 turbo and and it's nothing like the original, and the air intake pipes have to be larger - Can anyone confirm what I have? Photo attached. Can these be interchangeable if I change the hoses?

new iac on the left, current on right

 

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The new one on the left is an AIC and controls idle via a signal from the ECU, but somehow doesn't look standard. The old one is an early style which controls idle via an internal bimetallic strip and is adjustable. They are not interchangeable.

PS - Or at least I don't think so. How many pins does the new one have in the connector?
 

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They both are two pin and have the same connector on each.
Well in that case I was probably wrong in my earlier post. If they have the same connector there's a fair chance it will work if you can connect the hoses.
 

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The old part is an Auxiliary Air Valve. In the US it was only on 8v engines with CIS. The electrical connector runs a heater acting on the bi-metal spring. It just boosts idle speed on cold starts, that's all. The connector supplies 12v whenever the ignition is on.
The new one looks like an Automatic Idle Control valve used on LH electronic fuel injection that responds to the ECU signals.
Note the parts have different names. The connectors may be interchangeable, but their function is not.
There are 2 and 3 wire AIC valves but only one kind of AAV.
I know nothing about which of the 3 a Lucas fuel system might use.
 

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The top part is for a 16V engine (B202 or B212) with a Bosch LH Jetronic ECU. The two pin version is, if my memory serves, used with LH 2.4 and 2.4.2 systems so goes into 1989 and up C900's. There is also a 3 pin version of that part used with LH 2.2 systems from 1985 to 1988.

It's usually called an 'AIC valve' and has a servo-like motor actuator to open/close a vane to manage the flow of air when the engine is idling.

The bottom part is only used on 8V engines which do not have any ECU (at least I've never found an 8V Saab C900 with an ECU!).

The principle is the same as the AIC, except it has a bimetallic strip to move the vane, and is again mainly for idling. It has no servo motor like an AIC does, and cannot be controlled (normally) other than by physically disconnecting power to it's heating element.

Craig.
 

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Everytime I see Craig's user tagline - where it says "Tronno" it always makes me say "eh"
 

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Discussion Starter · #8 ·
Everytime I see Craig's user tagline - where it says "Tronno" it always makes me say "eh"
It's the lazy way to say toronto, but then I see NSW - HUH?

Going to try running the car without the valve, as I suspect the valve sticks causing bunnyhopping when slightly pushing accelerator.....

Thanks for your help
 

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I'm assuming this device acts like a choke, or is a choke? So in order to run it without I would disconnect the cable and block both hoses?

I know it isn't ideal but having difficulty getting another one that works. Its too difficult to drive smoothly once warmed up.
 

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It's the lazy way to say toronto, but then I see NSW - HUH?
But when you're from Toronto, it's the only way it's said :)
 

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near to where I live in Norfolk UK there is a town called Hunstanton, called by the locals hunston, and the is also a really odd one which is Happisburgh pronounced Haisborough, (sometimes written Haisboro)and both names appear on the maps, same spot lol
 

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I'm assuming this device acts like a choke, or is a choke? So in order to run it without I would disconnect the cable and block both hoses?

I know it isn't ideal but having difficulty getting another one that works. Its too difficult to drive smoothly once warmed up.
Yes it's a bit like a choke since it controls the amount of air bypassing the throttle valve plate at idle.

You could possibly remove it and join both hoses but then there's no controllable restriction on the airflow, and the ECU would have no idea what to do at idle as the O2 sensor signal plus the signal from the airflow sensor wouldn't be enough for the idle control part of the firmware in the ECU to work properly. At least that's my understanding of it.

When not in idle, the ECU doesn't use (? open to correction from someone) the IAC device, so I don't know if it's default state with no power applied is fully closed off or in a pre-determined partly open position.

This pic is on the B202 engine in my Saab 9000, but the setup with the throttle valve, IAC, etc. is the same as with a B202 engine in a C900:



flickr page

My 9k is a 1990 build, so it has LH 2.4 that still used a microswitch-based throttle position sensor. Not sure if that has any effect on how the ECU decides whether to be in 'idle' mode or not.

Re 'Tronno' he he yeah it's not Tronno ON (as in Ontario Canada). I have been there in the mid-90's. It's the 'other Tronno' which is the west side of Lake Macquarie near Newcastle NSW. :cool:

Craig.
 
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