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Discussion Starter · #1 · (Edited)
Hi all,

Thought I'd give back and refresh the thread on IACVs. My DIY experience is very novice so I thought I'd break it down, noob style. If I can do it, so can you!

Symptom: While driving, when I shift to neutral to coast the RPMs erratically bounces anywhere from 200 RPMs to 1200 as if gasping for breath. In fact, while turning in neutral once I had the engine completely stall out on me, which was scary as I lost the power steering. After a freaky experience last week, I decided to tackle this project this memorial weekend. I did my research and am going to recompile the DIY with existing and new references:

First, I started by using this excellent reference: http://www.celicahobby.com/forums/u...-Air-Control-Valve-How-To-Properly-Clean.html.
It seems like you can pair this maintenance procedure with a complete Coolant Flush + bleed since you will lose coolant from this procedure.

Stuff you should get (Cheaply!) from Harbor Freight Tools FIRST before attempting this:

The part that I got stuck on(along with everyone else it seems) was removing the coolant hoses. I believe these hoses feed into the heater core. In this step, it says to remove the hoses first from the throttle body


I found it easier to do this step LAST.
  • First, remove the plastic pipe that feeds into the ECU by prying it out and off
  • remove the thick air hose that connects the throttle body to the airbox/MAF,
  • Remove the 2 12mm bolts and 2 12mm nuts on TB using an extender
  • disconnect the big hose on top of TB
  • Disconnect throttle cable from valve
  • Unplug two sensor cables from TB (Refer to celicahobby link for pics)
  • remove the flappy metal gasket (this one is reusable) once you pull off the TB
Once you pull off the TB and set it on its side, which exposes the two coolant hoses. You'll need the short pair of pliers to scoot back the clips. Holy shit this was painful point #1 as the clips were pointed downwards and it was very hard to get in there, even with a short pair of pliers. Once I scooted the clips back it seemed like the hoses were stuck!! I used a flat head to screw driver to try to loosen up the edge of the hose. The hose closer to the battery is the one which coolant flows from, but pretty much expect coolant to spray anyway. You will need to bleed the coolant after this procedure. Once I disconnected the hoses I plugged them with the bolts from the throttle body, haha.

Once you have the throttle body with the IACV attached removed, begin by spraying Throttle Body Cleaner and cleaning out with a paper towel. Pull back the valve and get in between there too. Once you're done with that, it's time to separate the IACV from the TB. The bottom portion (3 screws).



This is where the impact screw drivers come in. Based off research on previous threads, it is nearly impossible to get these screws off using a normal screw driver. Pound the tool with a hammer while unscrewing. Impact screw driver saved me MUCH time and trouble. Once that was off, carefully separate the IACV from the throttle body. From there, use Q-Tips sprayed with TB Cleaner and clean that sucker out!! First pic is before. Pic after are my Q-Tips after cleaning:



Afterwards, put everything back and and connect all the hoses, sensors, bolts/nuts, and throttle cable. You will now need to BLEED the coolant because there will be pockets of air in the system from the coolant spraying out of the hoses.

Comprehensive Celica Coolant Flush+Bleeding Procedure here. Post #67


(IF YOUR CAR SHOWS ANY SIGNS OF OVERHEATING, TURN IT OFF!) What I did was top off the coolant reservoir with distilled water (The arrow pointing to "This One" will start dripping out any excess water), turn on the car until the fan started blowing (helps to rev a bit), wait for the fan to turn on thus letting coolant into the radiator. At this point you should SLOWLY unscrew the bleed plug while wearing gloves to let the air bubbles escape. It is hot. It is also important to turn on HEAT to FULL BLAST without AC. Your heater should be blowing hot air. Again, make sure the bleeder plug is unscrewed to let any air pockets escape. At any time when the coolant drops below "Low", stop the car and refill with distilled water.

Once all that is done, take the car out for a local spin. Heater should blow hot air. At the end, make sure your coolant levels are still filled. I opened the bleeder one last time to make sure all air pockets were out.

YOU THINK YOU'RE DONE, but not YET. 95% of the work is though!

NOW, you can follow this excellent guide and last important step from Blue Bomber:
http://www.newcelica.org/forums/showthread.php?t=123383

Don't be afraid of flooding the IACV hole with TB cleaner lol. I know this because my car sputtered on start up. I actually repeated this step a couple times. This ensures that the TB cleaner goes through the entire route that the Idle Air would go through for the stuff you just cleaned out.

Now my car coasts at highway speeds in neutral at a perfect 1k RPMs without gasping for breath. THANK YOU Celica community!!
 

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I haven't seen the OP's name in a long while.
I did something similar while my 1zz was somewhat in pieces. Lots and lots of buildup. OCD kicked in and it took a while to get all the nook and crannies cleared out.
 

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Discussion Starter · #4 ·
Ah Smaay and Zero, you two have helped me countless times in the past lol. Still run the celica strong as my Daily Driver. I didn't plan on getting this stickied, otherwise I would've took more pics. I was just hoping people would come across IACV cleaning sooner or later and stumble across this.
 

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I also swapped the phillips bolts for allen. I figured if I had to do it again it would make it a little easier.
 

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I just did this procedure and I drove around hoping my ecu would make adjustments but its still bouncing from 900 to 2000 while coasting then settles at 1400 at a complete stop. What else do I need to look at?
 

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I'm probably going to have to do this as well soon.

Not looking forward to it, since the Blitz supercharger adds a LOT of things in the way. :marky:
 

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Adding my two cents

First off, I want to say thanks to Rhace GTS for posting this! It was a huge help.
Feel free to call me on any of the following points / clarifications if you disagree.
  1. Why would you use distilled water to top off your coolant? Distilled water is great, but I would use an appropriate mix, typically 70/30 or 60/40 antifreeze to water.
  2. Yeah, hoses can be tough to crack free when they "glue" themselves onto a fitting. Usually some *gentle* twisting with pliers (assuming the fitting can take the stress - no problem, in this case) will break them free, and help get them off by twisting back and forth.
  3. I used penetrating fluid and Lee Valley "Screw Grab" along with a nice, sharp screwdriver, a few hammer taps, and lots of down force on the screwdriver (along with an adjustable wrench on the hex shaft) to get the IACV screws loose - and I still stripped one of them. I had to drill it and use a screw extractor (Princess Auto - I am from Canada, in case you hadn't figured that out :>). I was lucky enough to have a spare of the right size handy as a replacement.
  4. Using the throttle body bolts as plugs for the coolant hoses is brilliant - they are exactly the right size.
I am curious why you recommended Blue Bomber's cleaning method as a last step - shouldn't the IACV already be clean at that point? This is how I ratched mine in the first place - cleaned the TB with carb cleaner, and all the crap went into the hole for the IACV, which is when I first started having idle speed issues.
deniance mentioned taking the IACV apart in post #19 on this thread: http://www.newcelica.org/forums/showthread.php?t=339137&highlight=clean+iacv+spins
I would highly recommend this, with one caveat: The screws that hold the "black box" onto the IACV are tamper-resistant Torx Plus. If you want to take these out with the proper tool, I highly recommend you hunt the tool down first. Please note - the tamper-resistant version of Torx Plus is a five-point pattern (NOT six, as regular Torx and Torx Plus). Regular tamper-resistant Torx is six-point with a small hole in the middle (to match a pin in the middle of the screw hole, which is easier to deal with by removing the pin if you have to). You can get the driver on Amazon, etc. In my case, I didn't want to wait, so I did a bit of research, and used a Dremel tool to grind a slot into the screwheads, then used a slot screwdriver to remove them. Luckily, these are not as much of a challenge to remove at that point as the three Phillips screws holding the IACV onto the TB.
Another note of clarification on the IACV: When you take it apart, it should spin freely (the shaft is on ball bearings). If it doesn't, you need to correct that by cleaning it until it does spin freely (keeps spinning for a second or two when you give it a quick spin with your fingers). Although it spins once it is apart, it does not actually spin in operation. It is really hard to tell from the pictures how it works. Once you get it apart, it is a lot more obvious. The center shaft is maybe 1/8" in diameter - I believe this is the "bar" referred to in other posts. If you imagine a tube or cylinder around this, maybe 3/4" in diameter, with a disc at either end connecting it to the center shaft, then cut away about 3/4 of the circumference of the cylinder, this is basically the design. This piece of cylinder is the "gate" of the air valve, and it rotates maybe 1/4 turn (I am guessing) in action to open or close the valve. The reason that this is important, is that when you reassemble the IACV after cleaning it, you need to have the little square metal "flag" at the top of the shaft in the correct position (I am guessing this is used as a postion sensor). If you don't position this correctly, when you go to put the plastic "box" back on, it won't sit flush if you don't have the shaft in the correct position. Don't force it! You just need to rotate the IACV (the flag will naturally rotate to the bottom because of the weight of the gate) until the plastic box goes back on flush.
One last clarification - you don't have to do a full flush of coolant, just the bleed part. And the bleed chamber is a way to trap air bubbles as they flow through the system - the idea is that the chamber should have no air in it, just coolant (this is incorrectly specified in another post).
Hope that all helps someone - I have had an incredible amount of help from the forums so far!
 

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The Service Manual suggests replacing the IACV gasket if removed. Are people doing this, or have they found the gasket to be in good enough condition for reuse?
 

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The Service Manual suggests replacing the IACV gasket if removed. Are people doing this, or have they found the gasket to be in good enough condition for reuse?
I didn't think it needed replacing, although I still haven't fixed my high idle issue :>) The gasket material is similar to an O-ring. It sits in a groove on the throttle body, and the IACV contact surface is flat. I didn't look at it under magnification, but it didn't appear to be degraded or flattened.
Even from my local Toyota dealer in Canada, it was under $10 to get a replacement.
 
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