IAC adjustment?

[T4Rscott]

Hi all,

Last week I cleaned my TB and IAC.

I noticed, while cleaning the IAC, there’s two screws on the back. Are these for adjusting the throw of the shutter in the valve? Has anyone tried to adjust this?

For me, it’s mostly curiosity. But, if it would help with idle issues it would be nice to have that info.

Thanks

 

[Malcolm99]

I haven't moved those, but I think you're exactly correct, I'm going to guess it is to calibrate the spring tension inside for the shutter valve that is effected by the coolant temp, and probably calibrated during assembly of each individual IAC by Denso for consistency throughout its normal operating range and for quality control before sending it to the Tahara Plant.

 

[gamefreakgc]

I have not, but I have adjusted the resting position of the throttle body valve. I adjusted it a full turn and it was WAY high, idled at 2000 RPM. Turned it back 3/4 of a turn and it's solid for me now. You can adjust it if you have a low idle issue. I would not try and adjust it the other direction to close the valve more as it might stick shut.

 

[Sparky 97Runner]

Yes, those screws will change the IAC adjustment that was set at the factory. What idle issues are you having?

 

[T4Rscott]

Yes, those screws will change the IAC adjustment that was set at the factory. What idle issues are you having?

It’s idling at 1000 rpm +-. It did this the last time I cleaned these components. Took about 2 weeks before calming down. Just before I did the cleaning, it was actually idling a little low, at times, about 550 rpm in gear.

I’ve tested everything in accordance with the FSM. It will mostly likely take a little longer to relearn as I only go back and forth from work, about 2 1/4 miles each way.

Today I got out and did a little bit of highway driving and noticed when I stopped at the store, it dropped to just below 800 rpm in park.

 

[Devbot]

Sounds like a vacuum leak to me

 

[Sparky 97Runner]

I had random high idle issues that I finally narrowed down to worn out linkage in the throttle body itself. I've seen threads where people have used springs or washers to help the throttle close properly when the linkage is worn. If your idle changes when you put physical closing pressure on the linkage then this is worth looking into. I finally bit the bullet and bought a new throttle body and my idle has been perfect ever since.

 

[19963.4lsr5]

It’s idling at 1000 rpm +-. It did this the last time I cleaned these components. Took about 2 weeks before calming down. Just before I did the cleaning, it was actually idling a little low, at times, about 550 rpm in gear.

I’ve tested everything in accordance with the FSM. It will mostly likely take a little longer to relearn as I only go back and forth from work, about 2 1/4 miles each way.

Today I got out and did a little bit of highway driving and noticed when I stopped at the store, it dropped to just below 800 rpm in park.

Yes if you changed the airflow through the IAC and throttle body by cleaning it it will have to relearn certain operating conditions. The two most important would be hot idle and cold start position at various temps.


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[T4Rscott]

I had random high idle issues that I finally narrowed down to worn out linkage in the throttle body itself. I've seen threads where people have used springs or washers to help the throttle close properly when the linkage is worn. If your idle changes when you put physical closing pressure on the linkage then this is worth looking into. I finally bit the bullet and bought a new throttle body and my idle has been perfect ever since.

That’s not the issue. Everything is tight and slop free.

 

[T4Rscott]

My kids got me a set of FSMs for Christmas, so, I will be using that to help determine my issue

 

[shadow247]

My kids got me a set of FSMs for Christmas, so, I will be using that to help determine my issue

I think you are on the right track already. Cleaning the IAC will certainly require the computer to "relearn". It's possible your cleaning my have knocked it out of adjustment.

Have you looked at Timmy's video? IAC Valve Testing and Cleaning - YouTube

 

[gamefreakgc]

If you want it to re-learn faster, pull the EFI fuse in the engine bay (fuse, not relay). It resets the fuel trims at idle as well as the learned IAC idle memory. It may drive a bit funny the first few days but will adjust quickly.

 

[T4Rscott]

I think you are on the right track already. Cleaning the IAC will certainly require the computer to "relearn". It's possible your cleaning my have knocked it out of adjustment.

Have you looked at Timmy's video? IAC Valve Testing and Cleaning - YouTube

I have watched it twice, lol