2004 Mazda MPV Stalling and Rough Idle: Replacing the Idle Air Control (IAC) Valve
Posted: March 21st, 2009 | Author: Jacob Hammond | Filed under: Problems Solved, Technical Stuff | Tags: automobiles, iac valve, idle air control valve, mazda mpv, troubleshooting | 49 Comments »I have owned a 2004 Mazda MPV LX since early 2006, and it has been a great vehicle so far. Plenty of room, fairly fuel-efficient, quite practical and very satisfactory on the whole… with one exception.
Starting around late 2007, the minivan started to occasionally stall while decelerating or braking. The RPMs would drop to near-zero and the engine would die. It only happened a couple of times over a few months but began to get more and more frequent as time passed. Generally it would only happen between 15 and 50 MPH, and only when letting off of the accelerator. After the first few times, I learned to avoid it by tapping the gas as I saw the RPMs plummet; if I did that in time, I was able to keep it from dying. If I didn’t however, my only recourse was to shift into Neutral, start the engine while rolling, shift back into Drive and keep going. Of course, this was quite unsafe, and by the time it was stalling once or twice every time I drove it, it was time to do something about it.
I did a bit of research online and found the occasional mention of a faulty IAC valve being the cause of stalling and rough idling. The folks at Kragen didn’t know what an IAC valve was, and I didn’t pursue it any further from there.
The van began to show a check engine light, so I took it in to the local Mazda dealership to have them check it out. It turns out the check engine light was the result of a sensor that was blocked by excessive carbon buildup in the intake manifold, which was caused in part by the stalling behavior. According to the tech, the stalling was causing the engine to run a richer fuel/air mix on restart (because it interpreted the stall as an indication of a fuel/air mixture that was too lean), and this frequently-richer burn was causing an undue amount of carbon buildup. They cleaned out the intake manifold with Seafoam (or a product like it), did a firmware upgrade, changed the plugs and wires (which I’d asked them to do as a maintenance step while they had it in there), and, $1,100 later, was given a clean bill of health. The MPV passed Oregon’s emissions testing, the stalling was gone and all seemed well.
A couple of months later, the stalling started to act up again, and grew in frequency as it did before. I did a bit more research and all available evidence still pointed at a faulty IAC valve. As it turns out, the folks at Kragen weren’t able to find the part I was referring to because it seems to go by several name/acronym combinations: IAC valve, idle air control valve, idle control valve.
Still not sure that a fix was in sight but willing to try it, I ordered a replacement IAC valve from an online parts retailer for around $65 and put it in. Replacement of the valve was very easy; it is attached to the intake manifold by two bolts, and has a simple wire harness attached to it. Here are two pictures showing its location on the engine. I saved these when I was doing my research and, unfortunately, can’t find the original source, but here they are:
Location of idle air control valve on MPV engine
Closeup of IAC valve
As you can see, the valve is fairly easy to locate. It should be in a similar location for the following years:
- 2002 Mazda MPV
- 2003 Mazda MPV
- 2005 Mazda MPV
- 2006 Mazda MPV
Years 2001 and earlier have the IAC valve attached to the firewall, but it should not be too difficult to find (the part itself looks the same as the one seen here).
Since installing the replacement valve around four months ago, the minivan has been running as good as it did when I bought it. There have been no issues whatsoever with stalling or rough running.
Update: Slightly better image of the IAC valve below.
It's the gizmo with the red circle around it.
Thanks for the post. We had the same stalling experience while on a road trip. The dealer replaced the IAC which was enough to get us back on the road. They recommended replacing the intake manifold to get rid of the carbon buildup but I didn’t want to do that away from home.
I am glad to hear your van is running well again. I think I will go ahead and bite the bullet on the intake manifold.
Jackson, I’m glad to hear that you found this post. The problem seems to be somewhat commonplace.
As far as the intake manifold is concerned, the mechanic gave me the understanding that the excessive carbon buildup was due in part to the rich fuel mixture that the engine was burning after stalling repeatedly due to the faulty valve. Apparently when the engine stalls like that, the engine’s computer attributes the stall to a fuel-air mixture that is too lean, and runs it rich as a result. Months of this eventually result in lots of carbon buildup.
Rather than replacing the entire manifold, you might be able to refurbish it, either at the shop (as they did with mine) or yourself, if you’re feeling brave, using Seafoam.
My 2004 MPV (with 90K miles) had the same problem on and off for several months. The engine turned off when I exitted the ramp or slow down.
Since there is no visible warnings(engine light on, etc) local dealers told me they have to duplicate the issues otherwise they could not fix the problem (I can imagine it cost me $$$ just to find the problem).
My friend, who is working at Ford, suggested me to change the Engine Management & Ignition module (Duralast TV281 BY PASS VALVE. Note 2004 MPV uses Ford 3.0 liters 24V engine). Since then I do not have any problem.
I examined the old part and it is sticky, with lots of carbon build up.
The part cost me $45 from an autopart store
My 2001 mazda MPV is having a somewhat different problem. It see
Jackson, Great post. I am having the same idle stalling problem on my Mom’s 02 MPV. I tried cleaning the IAC resulting in a small improvement. I will try replacing it.
I could not read the codes with several readers I tried. I wonder if the dealer “firmware upgrade” will help?
Mike
Very interesting — looks like the bypass valve that you replaced is the IAC valve. It seems to go by a couple of variations on a couple of names which serves to increase the confusion.
Mike, it sounds like a replacement may do the trick for you. I’m surprised to learn how common this problem seems to be.
As for the firmware upgrade that the garage performed, I’m not sure if it helped with the problem (since the stalling problem came back, leading to the eventual and final solution of replacing the IAC valve), but I did realize some noticeable improvements in the automatic transmission’s shifting.
Funny you mentioned this. Today the my 2004 Mazda MPV reved up and stalled. It then was hard to start. Finally started and is running fine. I wonder if the same problem.
I have a 03 lx with the same stalling issue. I tried cleaning the IAC valve and it made it worse. After cleaning the car would only idle. As soon as you put it in gear it would stall.
I purchased a new IAC valve from Advance Auto Parts for $55. My local Mazda dealer wanted $65 for the part and another 17 for the gasket????? Plus, the part from AAP came with the gasket. The IAC valve is on held on with two 8 mm bolts and one plug. I changed the part in less than 5 minutes and it runs great.
Glad the new IAC valve fixed it for you.
For those interested, or those who can’t find the part locally, PartsGeek has it for $57.95:
http://www.partsgeek.com/gbproducts/YN/B18094-HIT-C4030.html
Thanks for the post. I replace IAC. My 2003 MPV ES still stalls and jumps but only when it is in gear and stopped. Anyother time it runs great. Took it repair shop, they replaced cracked intake hose from air cleaner helped for awhile, $500. 00 later, back doing the samething Any suggestions?
If it is skipping at idle and while in gear, it may be a failing ignition coil. I’ve had one fail already and another one is on the way out now.
More information:
http://mazdaforum.com/forum/archive/index.php/t-2695.html
Since the first one cost me around $400 to replace at the shop, I’m going to replace all six myself and hopefully prevent the problem from occurring again. The most inexpensive set of coils I could find is from this eBay retailer for $115+$10 s/h (do a search for “mazda mpv ignition coils”):
http://myworld.ebay.com/global-automotive/
I’ve got an ‘03 MPV. The check engine light came on, so I got AutoZone to read the codes for me. There were two: bank 1 mixture too lean and bank 2 mixture too lean. The advice shown by their system was to check the MAF sensor, fuel pressure, vacuum leaks, and O2 sensor.
I pulled out the MAF sensor and saw some carbon buildup on the fine sensor elements in there. A few shots of CRC electrical contact cleaner removed the buildup revealing shiny sensor elements. I disconnected the battery for a couple of minutes, reconnected it, and took the van for a test drive. There was no check engine light, but now, I noticed the idle was slightly rough.
I removed the IAC valve, leaving its wiring connected, and had a helper switch the key from ACC to ON and back a few times. I could feel the IAC valve jerk a bit with each move of the key, but the pluger did not move visibly from its position of about 2mm from closed.
I think I’ll pick up a replacement IAC valve and install it. I hope my results are as good as yours!
John, you might also try some CRC and/or other kind of cleaner inside of the IAC valve — since replacing it, I’ve heard from a couple of people that cleaning the valve has been effective, if only as a quick fix.
Thanks for the tip. That sounds like it’s worth trying if I’m planning to replace the IAC valve anyway. However, I was able to wiggle the plunger with my finger, and it seemed to move freely.
How is it actuated? In other words, in the shiny can, is there a solenoid, or a stepper motor, or a servo motor, or something else?
I’m fairly sure it’s a solenoid, but I’m not 100% on that. I know that older Ford engines used a solenoid-powered IAC valve, so I would assume the MPV uses the same type (Duratec engine).
My 2002 Mazda MPV LX has the similar problem. It would start, then die. This happens about once a week. After successful starting, it can run without any problem. I took out the IAC valve. Cleaning with acetone( the only cleaner in hand) and put it back. The starting problem never appear again. Thank you very much for the post!
It turns out my IAC was just fine. I put a new one from AutoZone on and the engine ran exactly the same.
Well, $936 later, the Mazda dealership has my ‘03 MPV running like new. They replaced the PCV hose, the back 3 ignition coils, and all 6 plugs. They said coil #2 had failed open. They also did the induction system cleaning process.
Now, my MPV supposedly got the 2004 PCV hose recall service done, but the hose I had looked like the old style hose with a U-shaped bend in it. Maybe they only inspected for a leak in 2004, and finding none, left the original hose installed.
John, very interesting — I forgot to mention in my post that while the MPV was being serviced, they also replaced the PCV hose.
By the way, ignition coil failure seems to be really common in 2002-2004 MPVs. The first one failed for me about 18 months ago, followed by a second one a few months ago. When the second one failed, I went ahead and bought a new set of six and replaced them all. The van runs like new now. Writeup in progress here: http://neveradudelikethisone.com/2009/08/replacing-ignition-coils-in-2004-mazda-mpv/
The fellow at the service desk said that lots of rear-bank coils fail, since they get hot between the block and the intake manifold. They gave me the two functional original coils in a box so I can swap them in should a front-bank coil fail in the future.
This was a HUGE help to use. 05 MPV was stalling on decel at about 40mph. Issue started 6 weeks ago and steadily became more frequent. RPMs would go up and down before stall. No other issues whatsoever. Dealer could not diagnose. Cost $250 for one pvc hose replacement which did not help. Googled found your posting, ordered IAC valve from Partsgeek and BINGO. We are NOT mechanics at all and this was a piece of cake. THANK YOU! We were so happy paid off the van the next day and will probably keep it awhile.
Awesome, very glad the post helped, that was my goal when I posted it
Thank you, Thank you, Thank you!!! I too have been to the dealer and because the check engine light was not on, they could not detect the problem. I replaced all the plugs, wires, air filter and over $1600 in repairs…I still had the problems. After a while, you learn to live with the dying engine at every stoplight, stop sign, curve and coming off the freeway was the worse. You can only rev the engine and shift into neutral to restart the vehicle so many times and hope no one will rear end your van!
Today I purchased the IAC from Auto Zone for $49.00. The installation was simple. I rev the engine and drove around without stalling. I can’t remember the last time I had a non-stalling drive!
Thanks for your post and I pray this is the answer I have been waiting for. During this recession, another BIG repair guessing game is not what my family needs. Again, Thank you!
Joseph, thanks for the comment. Glad to hear that you’re back up and running properly!
I have an 03 MPV with about 65k on it. Rough idle issue but no stalling. I replaced the IAC but the problem still remained. A buddy of my came over and we checked hoses by feeling around. A hissing sound was comming from the PCV hose. Found a recall notice for the hose but the dealer said the recall was already performed a couple of years back. So I bought the hose and replaced it. The old hose seemed like the old style cause the new hose is ribbed on the bend. Anyway that fixed it. When this first happened, the engine light did not come on right away. After I reset the engine light, (I was told to disconnect the positive terminal on the battery and hold down the brake for 5s) the engine light came back on but not right away again. I guess I’ll have to get the code read to see what it is. But the van seems to be running just fine.
Here’s the link to the PCV hose recall if anyone needs it…
http://www.mpvclub.com/recalls.php?id=17
Oh my gosh, when I found this post I wanted to cry! I LOVE my Mazda MPV (2004, bought used in May 2009) but it started doing all this stuff in August and has been really stressful for us since we travel all the time for dog training and dog shows (and my husband is stressed when I’m driving the van alone). The Mazda dealership is really snarky with us and insists on running these expensive tests, but a lot of posts I’ve read online say the tests yielded nothing. A Mazda mechanic told us that it could be PCV and said to buy carborater cleaner from AutoZone, spray it at the intake while the engine is running and if it revs up or down, it’s the PCV. My husband just did this and nothing happened so we were back at square one. Then I found this post and this is *exactly* what we have been experiencing! I didn’t know how to describe the problem, which is why months of research hasn’t helped. The term “rough idling” was the term I needed all along.
We also have a problem where the van turns off randomly in wet conditions. I see someone above posted a link about replacing coils. We think we may have both issues, not sure if they are related but we are bringing both these posts and printouts for buying the parts to our local mechanic for the labor.
THANK YOU!!!
Hi,
I have a mazda MPV 2004 and have been having the same problem. The dealer told me that the first step that needs to be done is to replace the IAC valve but he can not guarantee that this will take care of the problem. If after replacing the valve problems persist I will need to pay for labor and part each time. I would have thought that if they replace the part and then someting else goes wrong they wouldn’t charge for labor but anyway. My question is where can I get the part and how easy it is to replace it? The dealer told me it woudl take 2 hours to replace the part. I am not handy at all and don’t have any tool.Is there a step by step guide available?
You mentioned as well that the coils fail as well. Can any mechanic replace the coils or I need to go to the dealership?
I am thinking of getting the IAC valve and the coils replaced together.
Kamal,
It should only take the dealership 15 minutes to replace the IAC valve. It’s a very simple replacement — you just need an adjustable wrench or a small socket set to remove the two bolts that hold the valve onto the intake body. Here are the steps:
You can order a new IAC valve online; I ordered mine from rockauto.com (they have a pretty good selection and the prices are right).
There’s also a good chance that you may need to replace one or more of your coils as well, but I would definitely try the IAC valve replacement first, since it’s much simpler and cheaper to replace than the coils, and might fix the problem by itself. If you do decide to have the dealer do it, I’d talk to them and find out exactly why they think it is going to take them two hours to do the replacement. You can even open the hood, show them the valve (find it in the pictures in my post) and make sure that is the one they are talking about. Don’t let them charge you for anything over 15 minutes for just that.
Thank you so much for the quick reply. I can’t see the pictures you uploaded but I am going to order the valve and replaced it. By the time I get the part , hopefully I will be able to see the pictures. I am looing at the rockauot website and they ask what type of mazda my car is: L4 MFI, V6 Fi or V6 MFI. Where do I find this information? When ordering the part online what part number should I pick?
I have a mileage of 67000. I am wondering if i should replace the coils anyway even though i don’t have a problem just to be on the safer side or i should wait for them to die. Is it ok to fix something if it isn’t broken?
Under which section is the IAC?
http://www.rockauto.com/catalog/raframecatalog.php
Kamal,
I’ve updated the original post with a better picture of the IAC valve’s location. Hopefully that helps. If you can’t view the image, check here:
http://neveradudelikethisone.com/wp-content/uploads/2009/03/IAC.jpg
Here’s a link to the IAC valve on RockAuto:
http://rockauto.com/catalog/raframecatalog.php?carcode=1433131&parttype=6072
Regarding the coils, if the IAC valve fixes it, I’d leave the coils and only replace them if they start to fail. When they do, you’ll notice that the vehicle will begin to “sputter” occasionally once it’s warmed up, especially on the highway or at steady speeds. It may only happen every 30 seconds or more to start, but if that begins to happen, it’s most likely a coil. Could be that you are one of the “lucky” ones and you have good coils though. I’ll be finishing a writeup of the coil replacement process pretty soon.
Thank you Jacob for all your help.
Do I need to get the standard motor part or the one that comes with the additional parts?(the airtex one)
The part from Standard Motor should work fine. I think the Airtex one is the same part but with extra photos of it from different angles.
Also, I forgot about this one, but this is the one I ordered:
http://www.partsgeek.com/gbproducts/YN/B18094-HIT-C4030.html
thank you so much! i was having a really hard time trying to diagnose the problem.
Thank you I replaced the valve. Haven’t had the problem since. Keeping my fingers crossed.
Kamal
I’m glad my wife found this site, too bad it wasn’t sooner. The exact same problems as everyone else is seeing so I will try the AIC valve now. The first time we brough it in the mechanics couldn’t diagnose it without a code so we paid the $85 for them to tell us nothing. They did clean out a few things (i can’t remember what) and did not charge us extra for that oh boy. It did seem to not stall for a little while so we thought it may have been fixed. Very frustrating because a little while later it started doing it again. We just got it back from a different mechanic who didn’t have any idea either but recommended a fuel system conditioning / cleaning. This was ok because it probably needed it anyways. He also recommended replacing the water pump because it is a common issue for the plastic fins on it to break and it will cause overheating. So we did that and replaced the thermostat at the same time. Within the week it stalled again. Spent aroudn $650 this time. I wish mechanics would research a little more or just know more common issues like the AIC valve since this is their profession and they should be aware if it is common. Not to say this would have fixed it but I like the idea of starting with cheaper solutions first and work my way up. Very annoying and we will be looking for another vehicle as soon as we can. Would not have purchased this van if we knew of all the little problem that came with it.
Went to start my van this morning and it turned over but would not “catch” unless i held the gas pedal down. As soon as i let go of the gas pedal it would die. Found this awesome site, took out the IAC valve, blew it out with compressed air, re-installed and it started up just fine. Still going to replace the valve though, but at least i can get the car running to go to the parts store!!!
Thanks again for posting this valuable info!!!
I already left a comment, but I wanted to comment again now that the work has been done. We got the IAC valve according to this post, and also did ignition coils according to the other post, and spark plugs. The computer codes indicated some coil problem. The mechanic said we might as well do spark plugs while he was working on the engine. All told, we replaced the IAC valve, all six ignition coils, and all six spark plugs. We bought the valve from the link above (Parts Geek) and the coils from the eBay store posted above. We got nice platinum +4 plugs at AutoZone. Since we are not car savvy, our mechanic did the work. The total we paid for parts and the labor was about $400. Not that bad considering how much it would have cost for the dealership or a commercial chain type mechanic to do all their own “diagnosis”. My van is running better now than when I bought it. We also had the trans fluid done (in addition to the cost I gave). I’m not sure if it was the valve or the coils or both. The valve was done a few weeks before everything else, and we didn’t have any problems between (we went on a 700mi trip between).
My friend’s MPV does the same things so now she’s going to ask my mechanic to fix hers.
THANK YOU, THANK YOU, THANK YOU! Like so many others my 2004 mpv was having the same problem. Stalling once every couple of weeks and always when I was coming to a stop. Over the weeks, it progressed to once a day and then to a few times a day. Not only frustrating, but quite dangerous! I bought the IAC valve from Mazda ($120 I think) and my dad installed it within 5 minutes! This was months ago and the problem has never happened again. I am so thankful I found this site the day before I was scheduled to have a diagnostics check, etc, done at mazda to resolve the issue. This would’ve cost me a pretty penny and they probably wouldn’t have found the problem and made me replace parts that didn’t need replacing! thanks so much!!!!
Jacob,
My kids just broke the seat handle behind the front passenger seat. I have been looking on the web where to find the part but it seems my only option is to order the part form the dealer.
Any suggestions?
kamal
Kamal,
Not sure on where you’d get a replacement seat handle. If the dealer wants more than $100 for a handle, my best bet would be to watch Craigslist for a Mazda seat that has a similar handle (not sure, but I’m guessing the handle isn’t unique to the MPV and would exist on other seats as well).
Hello everyone. This seems to be an excellent forum and I’ve enjoyed knowing that I’m not the only one suffering (misery loves company
)
My van is doing what many others here are doing – rough idle in park, reverse & neutral. Also, the CEL comes on and struggles to accelerate. Plus it stalls here in there when pulling out of the driveway or into a parking lot.
I’ve replaced the IAC and that seems to have done nothing.
The majority of the tips state that users have replaced the plugs and coils mainly. I plan on doing that, but my concern is that so many have already done that and now they’re back to the vehicle having the same or similar problems. I guess my question is…is there anyone that has replaced the plugs and coils and had an excellent long-term outcome?
With my growing family, I’m debating trading the van in and getting a suburban. Any suggestions?
Thanks!
Danny,
The IAC valve and the coil are two separate, albeit related, issues. Symptoms of IAC valve failure are stalling on deceleration from 2,000+rpm (e.g. coming off of a highway offramp), whereas the rough idle and stalling issues you’re describing sound much more like coil failure. (Additionally, the CEL is probably indicative of coil failure. A bad IAC valve can eventually cause a persistent CEL because the engine computer detects an IAC-caused stall as being caused by an air/fuel mixture that is too lean.)
The trick to fixing the coil problem once and for all is to just go ahead and replace all six at once. They have a tendency to fail at different times, which is why you hear about people taking the vehicle to a dealership, getting the bad one repaired, and having another fail later on (which is what happened to me). Having a dealership or garage fix all six at once is prohibitively expensive for most, but definitely worth the time and cost ($120+s/h for six coils) if you do it yourself.
I’ve put around 30,000 miles on my van since the replacement and it runs great.
In addition to coil replacement, I also recommend using an engine cleaner like Seafoam before or immediately after the replacement, since a bad IAC valve can cause a lot of carbon buildup due to the engine computer running the air/fuel mixture too rich due to the repeated stalling.
One more thing: I highly recommend running an all-synthetic oil such as Mobil 1. I started using it around 5,000 miles ago and have noticed better power, smoother starting and markedly improved fuel economy (highway range on one tank went from 375-410 up to 440-475).
Forgot to mention too: check my last comment on this post for updated links to a complete coil-replacement guide and the retailer who sells the coils.
http://neveradudelikethisone.com/2009/08/replacing-ignition-coils-in-2004-mazda-mpv/#comments
I have a 2004 Mazda Mpv ES. I have been told the O2 sensor is bad and the number 4 plug is mis firing. I have had that same plug replaced 3 times in the last 10 monthes. Any suggestions. Looking for layout of where o2 sensors are located.
Thanks for this posting this fix, i was just about to pay Mazda a little oveer $1000.00 to fix this issue, after reading your post I went to mazda to buy the part, and they wanted $130 for the same part and another $35 for the PCV hose. again thanks for saving the strugging class some money.
i am looking for location of fuel filter for mazda mpv lx 2000
To find out how to change the fuel filter, try these two posts:
http://forum.mpvclub.com/viewtopic.php?t=13536
http://forum.mpvclub.com/viewtopic.php?t=13762