Can somebody please explain in details how the attached IAC valve works.

In particular, I am very interested if the coolant influences on this particular IAC valve’s operation or the coolant just transits through the valve and does not have any influence on the valve itself.

In other words, if there is any thermoelement inside the valve so that the coolant temperature can control idle RPM. Or, the coolant does not control idle and is necessary here only to warm the throttle body?

Many thanks in advance!

P.S. The picture was originally posted by MazRedMen at http://www.mazda626.net/index.php?showtopic=25028

[IMG]local://upfiles/5111/461CC3B26A464B2BA8E03A093824CB86.jpg[/IMG]

 

Hi again Sirob

The pic and description from the post were for a 98 626. The IAC on 98 and later 626 is purely electrically driven by duty cycle from the PCM. Even during cold start operation the PCM is opening up the IAC valve to gain the elevated RPM level needed at that time. The cooling hose and passages are just there to maintain a warmed up temp for IAC and Throttle Body.

You notice in the post that another member had a pic of a different looking IAC off of a 97 626. That IAC and all earlier are a two function part. It does still have the electrical solenoid that the PCM uses to control idle speed by changing the duty cycle based on various operating conditions and loads. During cold start however, they differ greatly. The 97 and earlier have a thermowax valve inside that is fully open when coolant is cold but that gradually closes as coolant flowing thru the valve begins warming the valve causing the thermowax portion to expand.
At a certain point during the warm-up cycle the thermowax valve passage will close completly and the PCM will begin controlling idle speed electronically.
Do not know what type you would have in the Ukraine as we have never had a 1.8l engine is a 626 as far as I know of in North American market.

By the way, did you get any replies about EGR and performance gains/losses. Do not know first hand as have never done this on a vehicle that I am familiar with driving. Had some theories though if you are interested still.

 

Thank you very much, babyhuey!

Can you please clarify what did you mean by “thermowax”? Was it actually special chemical wax which can expand and contract?

I attach one more picture. Is that a bimetal spring inside that IAC? Many thanks.

As to EGR I have not received any replies and will therefore be very grateful for all the theories / opinions you may have.

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Hi babyhuey!

Just to tell you that I already found a lot of info about thermowax and you may not reply on that question.

Just would be grateful for your opinion on my second picture. This is throttle from 626 GE ‘91 FS 2.0 L engine. Do you know whether it is thermowax or bimetal spring IAC?

 

That style would still be a thermowax valve. The valve would move from left to right in your picture as it is warming up and closing. The spring is there only to smooth the closing rate for a steady and gradual idle speed decrease and also to help fully open the valve as it cools down.

 

Sirob, You are from the Ukraine and I was trying to help safa from Moscow with an MPV problem but we had a very hard time in the translation process. Could you perhaps read the post and see what you can translate. Any help would be much apperciated.Below is the link to the post. Thank you.

https://www.mazdaforum.com/m_15606/tm.htm

 

Hi babyhuey! Just posted some info here https://www.mazdaforum.com/m_15606/tm.htm

 

Thank you Sirob. I really appreciate that.