IAC Valve Gasket and Throttle body intake rubber boot

MARK NICHOLSON2

MEMBER
1999 TOYOTA 4RUNNER
3.4L
VR6
4WD
MANUAL
242,000 MILES

I cleaned my throttle body and IAC after viewing your YouTube video, (nice job on the video). When I cleaned the IAC, I removed the rubber gasket to clean everything. When reinstalling the gasket, it was loose, or bigger than the grove it sits in. I worked it in the grove and slowly tightened the 4 screws while keeping it in place with a dental pick. I am not 100% sure I got it in correctly.

I also noticed upon reassembly that the rubber boot that connects the air intake to the throttle body is split. While installing, it split further (see image).

When I cranked the cold car (54 degrees), the idle was much higher than normal. When it did go down, it was still high and didn't get to near normal until an afternoon trip when the air temp was about 73 degrees.

Should I replace the gasket on the IAC, or is the new one going to be "large" also? Would a incorrectly installed gasket or the split cause the high idle or does the vehicle need to re calibrate itself?

Thank you in advance,
Mark

3 Replies

KASEKENNY

MECHANIC
18,907 POSTS

Couple things. First, I would change the gasket. Unfortunately once those are taken off they do have a tendency to expand especially if they are exposed to oil or chemicals.

Second, if the throttle body is cracked then it could be caused a high idle due to potentially unmetered air is coming in. The picture did not attach so if you could try to attach it again that would be great to see.

Also, Toyota says not to clean your specific IAC because it could damage it but this is unlikely. If all else fails, we may need to replace it but we can adjust the idle down if needed.

Let me know what you find and we can go from there. Thanks

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Monday, January 6th, 2020 AT 7:38 PM

MARK NICHOLSON2

MEMBER
2 POSTS

Thank you for the reply. Some follow up on this; I drove the vehicle on Monday and it ran fine. I believe the computer needed to re-set to the newly cleaned throttle body.

I did order the gasket for the IAC, though it appears I installed it correctly.

I have also attached the picture of the cracked rubber air hose that feeds into the throttle body. It does not seem to be a problem though I did order one of those too.

I didn't realize that Toyota does not recommend cleaning the IAC. How is the idle adjusted, just in case I want to tweak this?

Thanks,
Mark

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Tuesday, January 7th, 2020 AT 5:59 AM

KASEKENNY

MECHANIC
18,907 POSTS

Very possible that the throttle needed to be relearned.

I may have mislead you a bit. It is not an idle adjustment but it is a throttle stop screw. This just means it won't let the throttle completely close. However, if the screw is not in the correct placement it could be holding it further open which will raise the RPM.

If I am looking at this picture correctly that crack is just before the throttle body. If that is the case it could effect the RPM. The reason is this is most likely after the air flow sensor. That means there is unmetered air coming into the engine which will effect the RPM.

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