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99 Corolla Idle Air Control Valve

by Toyonis, August 8, 2010



I understand that the IAC valve requires pereiodic cleaning. As I have a slightly rough/low idle with my `99, I have cleaned the throttle body as best I could without removing it. My next step is to clean the IAC valve. Has anyone done this? I assume throttle body cleaner is the stuff to use. It looks like the valve is attached to the throttle body with two torx screws. Unfortunately T-15 is too small and T-20 is too big. Is there a gasket to replace?

There is a gasket, but can be reused. Take a closer look at the bolt heads - may not be Torx, could need to use a 5-sided spline. Some are socket caps, some are double hex socket caps. Most owners end up rounding out atleast one of those bolts. If that happens, just replace them with more conventional philips or socket cap bolts.

As for the solvent, plain throttle body cleaner will work just fine.

Upon closer inspection, yes, the bolt heads do require a 5-sided instead of the 6-point torx tool. I will find the correct tool and proceed. Thank you.

Upon closer inspection, yes, the bolt heads do require a 5-sided instead of the 6-point torx tool. I will find the correct tool and proceed. Thank you.

MAF O2 sensor contacts are also worth cleaning (remove 2 Phillips screws to get at it). I used CRC contact cleaner to clean mine. Another common item worth taking a look at is the PCV valve. The PCV valve in my 2000 was so gummed up I simply replaced it ($10 for an OEM replacement). I had a similar problem as yours, except to the point that the car would stall when cold. I thought I had it fixed after replacing the PCV valve, but its still there. My next step is the same as yours - to clean the IAC valve.

The bolts on mine are so badly stripped I can't tell what they originally were. I picked up some heavy duty hand tools yesterday that included various types of pliers, so I might finally be able to get them off, and when I do I'll replace them with simple Phillips of the same size.

-Spyder

Upon closer inspection, yes, the bolt heads do require a 5-sided instead of the 6-point torx tool. I will find the correct tool and proceed. Thank you.

MAF O2 sensor contacts are also worth cleaning (remove 2 Phillips screws to get at it). I used CRC contact cleaner to clean mine. Another common item worth taking a look at is the PCV valve. The PCV valve in my 2000 was so gummed up I simply replaced it ($10 for an OEM replacement). I had a similar problem as yours, except to the point that the car would stall when cold. I thought I had it fixed after replacing the PCV valve, but its still there. My next step is the same as yours - to clean the IAC valve.

The bolts on mine are so badly stripped I can't tell what they originally were. I picked up some heavy duty hand tools yesterday that included various types of pliers, so I might finally be able to get them off, and when I do I'll replace them with simple Phillips of the same size.

-Spyder

It's just MAF sensor. The O2 sensor is something else.

Bad_dude

Upon closer inspection, yes, the bolt heads do require a 5-sided instead of the 6-point torx tool. I will find the correct tool and proceed. Thank you.

MAF O2 sensor contacts are also worth cleaning (remove 2 Phillips screws to get at it). I used CRC contact cleaner to clean mine. Another common item worth taking a look at is the PCV valve. The PCV valve in my 2000 was so gummed up I simply replaced it ($10 for an OEM replacement). I had a similar problem as yours, except to the point that the car would stall when cold. I thought I had it fixed after replacing the PCV valve, but its still there. My next step is the same as yours - to clean the IAC valve.

The bolts on mine are so badly stripped I can't tell what they originally were. I picked up some heavy duty hand tools yesterday that included various types of pliers, so I might finally be able to get them off, and when I do I'll replace them with simple Phillips of the same size.

-Spyder

It's just MAF sensor. The O2 sensor is something else.

Could some one please tell me the locations of these two valves, IAC and MAF sensor?

Thanks.

The IAC valve is on the throttle body itself. Like a rectangular box that hangs off the bottom of the throttlebody. Will have some odd lookign screws holding it on.

As for the MAF - I believe you don't have to worry about that (you have a '99 Corolla?) MAF sensors were only installed on 2000+ Corollas, the 1998-1999 Corollas were MAP based, that sensor cannot be serviced - its location is close to the firewall. The cars equipped with MAF sensors, that is attached to the top of the intake box. Will have an electrical connection hanging off of it, located roughly at the highest point in the airbox.

The 5-point torx screws (T-20) ended up attaching the IAC electrical connector/actuator to the rest of the valve housing. Apparently the valve is located inside the metal housing you are referring to hanging on the bottom of the throttle body. An inspection mirror revealed philips screws attaching the IAC valve to the throttle body. After removing the electrical connector/actuator for better access and trying different philips tools, I was not able to get the proper leverage to remove the screws without stripping them--very tight work area. My Haynes manual calls for removing the throttle body for access. I agree to get the proper leverage. A new throttle body gasket would also be required. So I will try other fixes first for my low/rough idle. Cleaning the PCV valve helped some. I have also added some Gunk Regane to my fuel.

You are correct--no MAF n the `99.

Bad_dude

So did you ever got the IACV off to clean? What exactly was the screws type? Philip or the 5 spline torx bit? Where to get the tool?

Thanks.

That kits has the T20 bit, but it is the conventional 6-fluted variant. Check the throttlebody, it will have 5-fluted screws.

Bad_dude

That kits has the T20 bit, but it is the conventional 6-fluted variant. Check the throttlebody, it will have 5-fluted screws.

What does Toyota do that?

^^^

To keep people from taking stuff apart that they want you to buy outright. Not just Toyota, but just about every manufacturer out there. See this all the time in personal electronics.

Bad_dude

^^^

 

To keep people from taking stuff apart that they want you to buy outright. Not just Toyota, but just about every manufacturer out there. See this all the time in personal electronics.

So could I find this special tool at a local tool store or does it have to be purchased online?

Thanks.

Bad_dude

Where's the valve located? Here's a pic of the front of the TB area, is that the IACV? It does have 2X 5 splint screws on it. The valve is the black plastic portion right? Or is it the metal area behind the black plastic area with the electrical connector on it? What's the best way to remove it? Is it just the 2 weird screws?

There's a valve that is directly behind this one, is that the TPS?

Bad_dude

I found this link on how to do it, but it's on a different year I think. It looks like you have to take the TB off to do this? And the black plastic part is no the valve itself.

IAVC cleaning.

You'll have to take the TB to clean it well. The idle-air valve is on the bottom of the TB, connected to the part that runs to the wire sticking out the front. That black plastic piece is the solenoid actuator - the valve itself is right being it. Can't really clean the plastic bit, but you can clean the rotating, metal valve.

Bad_dude

You'll have to take the TB to clean it well. The idle-air valve is on the bottom of the TB, connected to the part that runs to the wire sticking out the front. That black plastic piece is the solenoid actuator - the valve itself is right being it. Can't really clean the plastic bit, but you can clean the rotating, metal valve.

In that case I should have the TB gasket ready for replacement.



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