Jump to content
Strawberry Orange Banana Lime Leaf Slate Sky Blueberry Grape Watermelon Chocolate Marble
Strawberry Orange Banana Lime Leaf Slate Sky Blueberry Grape Watermelon Chocolate Marble
djdevon3

Iac (Idle Air Control) & Throttle Body Cleaning (1993-2002 I4)

Recommended Posts

Here is an IAC module off an older MX-6. The throttle body and IAC are slightly different from the 93-02 626 but all the cleaning procedures are the same.

http://www.youtube.com/watch?v=NBMT53dxq8o

Took me a while to do but finally laid down a nice comprehensive series of videos detailing the 626 IAC cleaning procedures and everything you should look out for.

Say Hello to the IAC plunger assembly. No, this isn't the part you want to disassemble if you are looking to clean your IAC. When I started removing the IAC I did believe this was the part that was causing my rough idle. Turns out most likely not the culprit.

As you can see from the image it's double spring loaded. Be very careful while removing not to drop any pieces. You need all of them to put it back together.

img-318447-1-P6110054.jpg

There was carbon buildup on the springs and plunger (red thing) but not enough to negatively affect its operation. This was a 16 year old original IAC and never previously removed. From what I've seen of the IAC and the IAC plunger assembly... there's no need to ever remove the plunger assembly but enough about that, let's do it anyway.

The large red metal piece is the plunger. It barely fits in the housing and glides in the cylinder like a pnuematic piston. It also has rings like a piston. The plunger is the weight which resists air/vacuum pressure. Depending on how much vacuum your intake manifold produces will affect the IAC plunger. If you have low vacuum due to a vacuum leak you will have a rough idle because the IAC plunger will not be in it's proper position and the sensor will tell the ECU to lower the idle. Voila there's your low idle/rough idle.

Freshly disassembled and cleaned with throttle body cleaner and an aluminum brush. Never use a brass brush on aluminum parts. Don't use your cleaning spray inside the IAC! It is a self-enclose non-serviceable part. See the large diameter circle around the plunger housing? That's where the electronics are pressed fit into the housing. There is NO way to remove the electronics from inside the housing. If you get liquid in there it will slosh around the sensor electronics possibly shorting them out. The only safe way I know to clean the inside of the plunger housing is to use qtips or spray with the part upside down so it can at least drain out immediately. Just be careful with it mmmkay, it's probably one of the most expensive sensors on your car other than your MAF/VAF. Use carb or brake cleaner on the springs. Using the brush on the springs works the best just be careful not to bend them. Those springs do have tension tolerances that the plunger depends on. Yeah you need to be delicate with everything having to do with that darn IAC.

This image makes it looks a lot worse than it really was. Just a little delicate cleaning is all it needed.

img-318447-2-P6110052.jpg

I recommend using a pipe cleaner to get in the coolant and bypass air passages. Don't recommend spraying anything down the tube because there is another side hole that goes into a sealed electronic compartment. There's no way to dry it out and my gut feeling was not to spray anything in there. Pipe cleaners worked just fine.

img-318447-3-P6110055.jpg

Reassembled

img-318447-4-P6110056.jpg

  • Like 1

Share this post


Link to post
Share on other sites

Part 2 of 3.

Details the throttle body and TPS removal process. Also diagrams how coolant is routed through the IAC and throttle body.

This is a pretty good video that will answer quite a few questions about part locations, removal, and cleaning. Finally a detailed video that explains everything about the IAC, TPS, and Throttle Body. I'm pretty happy about this one. I did accidentally call the intake manifold the throttle body once but whatever.

  • Like 1

Share this post


Link to post
Share on other sites

Part 3 of 3

Covers tips on cleaning and gasket recommendation.

 

Update: 03/26/2014

We've had many reports of coolant leaks within the IAC due to the O-rings not properly sealing after reinstallation.  Therefore it is now recommended that if you do this procedure that you replace both the gasket and O-ring with stock replacements.  Only attempt to make your own gasket if you are desperate.  You can find both at RockAuto.com fairly cheap which I did not know at the time I wrote this tutorial.  In the future if the gasket and O-ring are no longer available then I can recommend you make your own gasket.  Until then it's definitely best to buy new replacements. 

 

1993-1995 IAC requires a separate gasket and O-ring.

1996-2002 IAC uses a rubber gasket that also acts as an O-ring, there is no separate O-ring on the 96-02 IAC.

 

A leaking IAC O-ring can exhibit similar symptoms to a blown head gasket with mysterious coolant loss and white smoke from the tail pipe.  The way to identify a leaking IAC O-ring will be coolant in your intake manifold.  If you've recently done an IAC cleaning then this means you'll have to remove the throttle body again in order to inspect inside the intake manifold.

 

I'll leave the part of the tutorial on how to make your own gasket just for informational purposes but I can no longer recommend it as part of the IAC cleaning procedure.

 

------------------------------------------------------------------------------------------------------------------------------------------------------

I recommend the Felpro black gasket material since it's rated for gas, coolant, and air. The blue gasket sheet is for coolant and air only. The black is a bit more expensive (by $1 or $2 more). The black fiber sheet is a more compact material so I assume it will last longer.

V6 owners: you CANNOT make your own gasket unless you remove the rubber seal around the entire IAC and have the mating surface machined flat. Sorry this is for I4 owners only. If you figure out an easy way to do it for the V6 please contact me.

img-318756-1-P6290093.jpg

Traced the pattern with an exacto.

img-318756-2-P6290094.jpg

Used the exacto knife to pierce holes and trace the inner sections. Exacto was definitely the right tool for the job. Took about 10-15 minutes to do. Hardest part about this is holding down the gasket so it won't move while cutting it. The factory black rubber seal you see is made of compressed rubber similar to a valve cover gasket. Over time it will get brittle and has a possibility to crack like plastic.. That is actually the coolant seal, what you are replacing is basically only used as a backup gasket for the coolant. It's also used to seal the air out between mating surfaces. It's more for the air passages than the coolant passage so not getting the area around the coolant gasket cut perfectly to shape isn't a big deal.

img-318756-3-P6290096.jpg

Please disregard the comment I made in the video. It was incorrect. The gasket did not blow out in that section. It was never there to begin with, on purpose.  There is a good chance that if you disassemble your IAC that you will need to replace the O-ring.

 

img-318756-4-626_IAC_Gasket.png

  • Like 1

Share this post


Link to post
Share on other sites

Here's some before and after images.

That caked on varnish is pretty easy to remove with carb cleaner and a soft aluminum detailing brush (available from any local auto part store).  Do not use the gold looking brass bristle brush as you can score the soft aluminum with it.  Looking at something like this you'd think a heavy cleaning is in your future. It really wasn't that bad.  This is exactly what carb cleaner was invented for.

img-318775-1-ThrottleBody_Before.jpg


The butterfly valve kept getting stuck which I've found out is a somewhat rare issue that only a few people have had over the years.  I believe it is due to burned valves.  If your throttle body looks like it's been through a fire that's because it basically has.  My intake valves were not sealing 100% and allowing combustion gas back into the intake manifold.

 

Yeah I'm proud of this one. Almost looks brand new.  I do not recommend taking a dremel to the butterfly valve.  It's made of brass and also has a special non-stick coating to allow air to flow over it easier and also make cleaning easier.  The bore of the throttle body is also coated.  It takes a lot of scrubbing with a brush, dremel, or sandpaper to remove the coating.  I highly recommend you don't clean it hard enough to remove the coating as that will simply make your throttle body require more frequent cleaning in the future.


img-318775-2-P6290090.jpg


Used tobacco pipe cleaners to get into the coolant tubes. Those were extremely clean already. The bypass air hole wasn't clogged up either. There was only a tiny bit of dusty carbon barely even worth mentioning. The backside of the butterfly valve, the entire IAC and throttle body were in remarkably good shape before the cleaning even though the caked on varnish suggested otherwise. A little surface cleaning and it looked good as new.

img-318775-3-StuckButterflyValve_zpseb1a
 

 

The most likely part of the butterfly valve to get stuck is against the side wall because the center of the valve has the most buildup.  You'll want to lubricate the center shaft on each side with grease.  Pack it in there any way you can so that the valve turns smoothly.  That's the key that finally did the trick.  I don't think cleaning it with a dremel is necessary you just need to clean out the grime and then lube up the center shaft on each side.  I didn't know what was causing the issue so along the way eventually the culprit was found and now you all can read about how to fix it too.  No more kicking the gas pedal before accelerating.

This was the original 16 year old throttle body and IAC. I would later find out that I have compression loss on a cylinder which I believe was contributing to the heavy carbon build up in the intake manifold. I also believe it played a role in getting my IAC plunger sooty. It wasn't sooty to the point that I even worried at all about it. My engine is about as bad as it could get without completely failing so if my IAC is in good shape chances are yours is too. The health of your engine plays the biggest role in the frequency of cleaning your throttle body.

Good luck and if you have any questions please ask.

  • Like 2

Share this post


Link to post
Share on other sites

You might think that all that black varnish is from the EGR system.  Nope.  I figured out later that my throttle body (and inside of the entire intake manifold) was so dirty due to a sticking intake valve and bad valve seat (commonly known as a burnt valve).  This allowed gas during the combustion cycle to blow back into the intake manifold.  Also causes a slight vibration, possible backfires, and potentially gummed up injectors.  It is possible for Seafoam to correct an issue like that if it's not too far gone.  Unfortunately mine was years too far gone.  The engine head had to be removed and taken to a machine shop to fix the valve issue.

  • Like 1

Share this post


Link to post
Share on other sites

I cleaned mine IAC and TB some days ago.Everything is fine till i drive the car for 10mins until reach working temperature of engine and when i put neutral on redlights or when i have to stop RPMs bounce from 500 to 1500RPM.While its cold theres no problems.

Sometimes they stuck to 1200 then again start bouncing after some seconds.Removed TB and IAC twice to ensure its not vacuum leak,installed original TB gasket and created one gasket for IAC and same result.When i disconnect the IAC RPMs are steady on redlights.I dont have missing springs or parts in the IAC,installed the springs in the holes correctly.

Share this post


Link to post
Share on other sites

Don't forget to burp/bleed the air from the cooling system and do an AAS adjustment if needed.

 

The IAC has a coolant line attached to it.  When you disconnect that it will introduce air into the system. Gotta make sure you get the air out of the cooling system.  This is a common occurrence to happen after an IAC cleaning.   Another thing to consider is after years of maintenance the effectiveness of your IAC and vacuum system might get tweaked using the idle air screw by mechanics.  If you suddenly fix years of adjustments you might need to readjust your air adjust screw back to factory settings.  The air adjust screw (AAS) can only be adjusted while the car is in diagnostic mode.  If you turn the screw while the car is not in diagnostic mode you'll notice that idle speed will go down or up then the ECU compensates for it,  therefore you waste time and effort.  The ECU does not compensate while the car is in diagnostic mode and you'll notice the AAS works as expected.  When you take the car out of diagnostic mode then the ECU will compensate for the new base RPM setting.  You want to get it to 750 RPM using the AAS while in diagnostic mode. It's recommended that only a mechanic does that so if you can't figure out your fluctuation it's best to have a mechanic take a look.

  • Like 1

Share this post


Link to post
Share on other sites

Yes,just burp it and no result-while waiting to turn on the radiator fan sometimes,engine was keeping 1400rpms,when i drive and put neutral then it bounce 500-1400.The idle air screw is with the factory paint over it so i think its in original position.I think ill have to replace the IAC,i guess the temperature sensor in the IAC is giving wrong information to the ECU?

Share this post


Link to post
Share on other sites

Do you or anyone know where to get a new rubber seal for the throttle body iac mating surface on an 2002 I4? The previous owner to my 626 saw fit to remove the gasket between the throttle body and iac, not replace it, and crank that puppy down to something in the range of 40 ft-lbs. I called my local parts stores and the nearest mazda dealership and they were of no use. I am unsure if the seal will still be functional when i use a gasket.

Share this post


Link to post
Share on other sites

2002 Mazda 626 4-cyl Throttle Body & IAC Parts Diagram

Mazda Part # FSD713W89 

You can call up your local Mazda parts department and ask them to order you the gasket from that part #. 

Official Mazda part #'s are on the right side, inside a small blue rectangle, above the cart icon.

 

GASKET, THERMOSTAT

$9.30

Share this post


Link to post
Share on other sites

I saw that but i thought it was only the gasket not the rubber o-ring seal. 

Share this post


Link to post
Share on other sites

Can you post a picture of what you're dealing with please?  Would be nice to have a picture of the 98-02 version for this topic.

Share this post


Link to post
Share on other sites

I am apparently a nutcase. You posted the correct part. Thank you very much. I'm in my engine right now asking "wtf, am I stupid?" My whole week has been a coffee deprived Monday.

Share this post


Link to post
Share on other sites

So this is the rubber seal i was talking about and DJ was correct. 

 

IMG_20140311_172750186_HDR_zps9522dcaf.j

 

For some reason I was thinking it was the same as the 97. I am very good at confusing myself. Thanks again for all the help.

  • Like 2

Share this post


Link to post
Share on other sites

Ah thank you for posting that!  As you can see there's a big difference between how the 93-95 seals compared to the 96-02.  The IAC designed changed in 1996 due to introduction of OBD-II.  If the seal leaks not only will you get coolant leaking into your intake manifold but you'll probably have an air leak too. 

 

Burning coolant and unmetered air leak = 626 instantly runs like hammered shit.

 

On the 96-02 it's much easier for that seal to breakdown and for coolant in the IAC to leak into one of the air passages beside it.  That means coolant will go into your intake manifold and eventually be burned in combustion cylinder. 

 

Important Note:

This is why you cannot automatically assume that mysterious coolant loss and plumes of white smoke from the tail pipe is a blown head gasket!  A leaking IAC isn't something most mechanics take into account on the 626 and has probably doomed many a 626 to the junkyard assuming they have a blown head gasket!!!  The symptoms of an internally leaking IAC are identical to a blown head gasket!

 

I'm not a fan of the revised IAC gasket for the 96-02.  Just look at how easy it is for it to leak into any of the adjoining air passages.  Thank you for sharing pictures.  Now 96-02 owners can see what they are dealing with.  Your image is going to help a lot of 626 owners. Thank you!

  • Like 2

Share this post


Link to post
Share on other sites

I've revised many things in this tutorial today thanks to new information provided by CMontCalm.  If you have images or information to contribute to any tutorial on this site please speak up.  Your experience is very much appreciated and can be invaluable to others in the future!

Share this post


Link to post
Share on other sites

I'll probably do a write up for the third gen 626 TB and IAC removal and cleaning as I'll need to do that on mine. I pulled off the TB from my shit parts car today and it took all of less than two hours. The process is a bit different, (like no screws, all nuts to remove off four bolts of two different sizes) and there is this pain in the crotch piece that bolts from the engine block to underneath the throttle body that you have to remove to get to the last nut and it's not easy at all to remove and in my case, it may actually need removal of the air box to give you more room to work on it. There's this one stupid bolt underneath the TB so you when you try to undo it, you need to finagle around the socket wrench just right because that bolt is angled with the TB. I had to use a metal pipe to pop it loose, hence why the air box needed to be removed. Bastard metal piece.... :mad: I don't know even know what the hell it's even needed for, it's just there to clip some harnesses onto it and a ground connector.

 

But speaking of such, the throttle body I removed to day was CAKED in filth. I never drove that car, but I can bet it had idling issues was it was just holy balls. Guess that's what a quarter million miles will do...  :huh: The IAC was as dirty as was in the video. I check the TB on my car as well and it looks quite clean. I only have 109,000 miles on my car and you can see the brass butterflies and tell it's brass, that's how clean it is. I never have cleaned it out before, but on the other side of it, it's a tad more dirty but not enough I think could possibly cause an idle issue. I don't know...

 

Also, how does one clean out the intake manifold? And once you clean out the TB and IAC valve, I've read that you may also need to reset the ECU by disconnecting the battery and holding the gas pedal down for about a minute. Is that needed to be done and is that even the right way to reset it?

Share this post


Link to post
Share on other sites

Only reason to clean the TB is so that the grime doesn't continue to pile up layer after layer, year after year.  Eventually it can get so thick that it hinders the valve from fully closing and/or can get stuck.  The TB is going to get dirty eventually that's just something every car has to deal with not just Mazda but every car on the planet that has a TB.  It's a maintenance item.  

 

Yeah you can reset the ECU that way on any version of the 626 even the OBD-II 5th gens.  Doing so will also clear all codes but sometimes you might not actually want to clear the codes if you're having an issue.  It depends on the situation.  If you're sure you want to clear the codes and reset the ECU then remove the negative battery terminal for a couple minutes.  You don't need to step on the brakes really it's just to help drain the power from capacitors by activating the brake lights.  if you were to only remove the negative battery terminal it really only takes about 15-20 seconds for all power to drain from the entire electrical system.  Stepping on the brakes just makes it go faster to about 5 seconds.

Share this post


Link to post
Share on other sites

Definitely of course throttle body cleaning is something that needs to be done on every car regardless, but in my case, I'm just wondering if that's even the actual reason why I have a rough idle is because of a dirty throttle body. I'd hate to have to go all the effort only to find out that wasn't even the cause for it because I've gone through mostly everything and I think I have about...four or five things left I can do to address and fix until the conclusion can be reached that something major is definitely gone to shit.

 

Oh well, I'll just do it either way to do it. I'll need to track down a couple of gaskets from Rockauto. Their shipping is preposterous though.

 

On another note, on your car, you disassembled the IAC valve? What was the reason behind that?

Share this post


Link to post
Share on other sites

No I don't think cleaning your throttle body is going to fix your issue.  Probably a vacuum leak and would instead recommend smoke testing your intake first.

 

To see if the plunger was sticking somehow.  It wasn't and I don't recommend anyone disassemble their IAC anymore.  It usually introduces more issues than it fixes.

Share this post


Link to post
Share on other sites

Hmmmm... I did some smoke testing around my engine bay and nothing seemed conclusive. I'll probably have to replace my flex pipe first as was kind of throwing things off near the injectors.

 

I also did some light cleaning of the throttle body. Mine wasn't too bad, but had some crud around it. It did seem like something improved slightly, I can coast in neutral and it stays at about 750 RPMs and when I stop in neutral, it stays at 750 for a few seconds and drops down to 650 almost. Once I put it into drive, same thing happens where it goes down to 500 RPM and back up to 600-650ish.

 

Gosh damn it all!

 

Other than that, I have not a single hesitation issue of any kind. I almost wonder if it's the IAC valve that needs checking but that the air way to it didn't even seem at all dirty....

Share this post


Link to post
Share on other sites

My car is throwing a code for the iac, and I recently cleaned my egr ports and throttle body. Car idles/runs rough

Share this post


Link to post
Share on other sites

How in the heck did you get the original gasket off?   Mine is baked on, with parts sticking to the manifold and parts sticking to the TB and it's hard as a rock.  Tried scraping it off with a knife, but stopped cause I was afraid to scratch the mating surface.  I just spread some naptha paint remover on it to see if that will soften it up.   Can't find any gasket removing compounds locally.

Share this post


Link to post
Share on other sites

Yeah when it's really old and brittle it will end up looking burnt from years of heat soaking. There is really hot coolant that runs through the IAC remember. ;)   I know exactly what you're talking about.  Best method is a razor blade.  You are right to be cautious about gouging the mating surface.  Be very careful with the razor blade and you'll get it off no problem.  Once all pieces of the gasket are scraped off then you can use a fine piece of sandpaper anything 800 to 1200 grit sandpaper will work great.  Smooth it down then install the new gasket.  The IAC gasket for the 2.0L is about 0.5mm thick fiber gasket.  There is some leeway with crush depth just don't make any huge scratches and the new gasket will take care of making a good seal.  Do not use any RTV or sealant.  You can get a new IAC gasket from RockAuto.com, local auto parts store, or dealership. 

 

There are different IAC designs for the 626 depending on year, engine, and trans configurations.  Ensure you get the right gasket pattern for your IAC. Some have similar looking maze patterns and can easily be confused for the wrong one.  Study the pattern carefully and select the right gasket.  Obviously you'll only know what your IAC pattern is by removing and disassembling it first.  If your local parts store doesn't have one on hand then it could be a week or so until your new gasket is ordered, shipped, and delivered.   Same goes for dealership or online retailer like RockAuto it could take some time to order and deliver.  Not all dealerships stock all items locally. 

 

Your 626 can run without an IAC (you'll have to bypass or plug some coolant hoses too) however please note you might have erratic idle issues during that time.  The IAC is the ECU's way of controlling air flow.  It's only 1 of 2 ways the ECU actually has physical control over A/F ratio.  It's a pretty important device for having a smooth idle and a good running engine especially during the warm up period (idle enrichment).

  • Like 1

Share this post


Link to post
Share on other sites

Can an IAC on the 98+'s be messed up to the point it's causing rough idling and hesitation during acceleration, yet not throw any codes?

 

I disconnected mine while idling, and the engine died, which is what the WSM says it's supposed to do, but I'm still wondering if maybe it isn't the source of my problems anyways, since my fuel trims are fine, and I've checked timing, compression, cam to lifter clearances, and both the cam and crank sensors, have a new air filter, no air leaks, good spark and used to vacuum gauge to check for exhaust restrictions.  I'm pulling my hair out.  There are no codes of any kind, and both the KOEO and KOER self tests pass with no problem, and I figure if there was an EGR problem or wiring problems with the cam or crank sensors I'd get a code.

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

×