Honda-Acura Surging Idle Speed (case study)

What causes a surging idle speed on a Honda or Acura?
Here, we’re addressing that complaint and what to look for when you run into this symptom. Honda has a unique programmed response to excessive idle speed, resulting in the distinctive Honda idle ‘surge’. Don’t be a parts changer and replace the IAC motor!
Engine Performance Diagnostics chapter 20
Symptoms
- surging idle when warm
Fix
- adjusting the cold fast idle valve
Tests shown
- how to scope test a fuel injector
- understanding how Honda/Acura controls excessive idle speed
- how to measure duty cycle on a computer controlled solenoid
- how to test the electrical IAC solenoid
- understanding common causes of high idle speed conditions
- understanding the operation of a Honda cold fast idle valve
- how to determine if the cold fast idle valve is operating properly
- how to test for a malfunctioning cold fast idle valve at the throttle body
- how to inspect and adjust a Honda cold fast idle valve
Tools used
- lab scope
Playlist
- (Chapter 20) Idle Speed Problems and Testing
• (Chapter 20) Idle Spee...
Related videos
- P0507 Idle Control System (RPM Too High) - vacuum leak - GM
• P0507 Idle Control Sys...
- Ford Idle Air Control (IAC) valve test (how to adjust minimum idle speed)
• Ford Idle Air Control ...
- P0506 IAC System RPM below expected (vacuum leak) - Ford
• P0506 IAC System RPM b...
- Ford idle air control valve (IAC) test - stalling problems
• Ford idle air control ...
For more information on this topic, I have written a “field manual” called Engine Performance Diagnostics which is available at www.scannerdanner.com as an eBook or paper book.
Want even more diagnostic training? Whether you are a DIY trying to fix your own car, someone looking to become an auto technician, or a current auto technician that wants to get more into diagnostics, subscribe to ScannerDanner Premium www.scannerdanner.com/join-sc... There is a 14 day free trial.
On ScannerDanner Premium I will bring you right into my classroom at Rosedale Technical College. You will find page for page lectures taken right from my book as well as exclusive classroom type case studies. What is so special about these classroom case studies? I pull live problem vehicles directly into my classroom and we troubleshoot them in real time, using and applying the theory and testing procedures we learn during the classroom lectures. There is no better on-line training of how to troubleshoot automotive electrical and electronics systems anywhere!
Disclaimer:
Due to factors beyond the control of ScannerDanner LLC, it cannot guarantee against unauthorized modifications of this information, or improper use of this information. ScannerDanner LLC assumes no liability for property damage or injury incurred as a result of any of the information contained in this video. ScannerDanner LLC recommends safe practices when working with power tools, automotive lifts, lifting tools, jack stands, electrical equipment, blunt instruments, chemicals, lubricants, or any other tools or equipment seen or implied in this video. Due to factors beyond the control of ScannerDanner LLC, no information contained in this video shall create any express or implied warranty or guarantee of any particular result. Any injury, damage or loss that may result from improper use of these tools, equipment, or the information contained in this video is the sole responsibility of the user and not ScannerDanner LLC.

[@dannyr3346]

8 years later and this is still the Go to video for all service techs dealing with old ass Honda's.. Truly a testament to scanner Danners knowledge and his journey to the answers.

[@unionpride525]

as soon as you figured out the the cold-fast idle valve was open and you could thread it in I was yelling at my screen saying, "YES! YES! That;s it dude!!" that issue was killing me and I went and did the exact same thing you did! right on brother. thanks for your videos

[@geronimoveneracion8057]

Brother. Hands down, the best and amazingly detailed video on idle (fast idle valve) problems out of the dozens of videos I've come across. Never stop posting these vids man!

[@ScannerDanner]

Glad it helped!

[@mr.nobody4900]

Thank you, Mr. Danner, for making this video it came to a huge help to me just yesterday dealing with excessive idle problems with my Honda after adjusting the fast idle valve the idle problem has gone away completely. Thank you.

[@catabaticanabatic3800]

Just bought a second-hand Honda and it had exactly this problem. Thanks for the video it has enabled a fix.

[@Shmelkable]

Thank you so much for this video, I've tried everything to fix my idle problem, from the pcv to the iac and nothing worked. This video helped me and it was easy to understand. I was able to do it in an hour after watching your video. I appreciate it so much, you've earned another subscriber. Keep up the good work!

[@JasonTylerRicci]

So glad I found your video! This video is phenomenal. My SOHC has exact same idle surge. Now I know where to start. Thank you!

[@EartAlienEB1]

You are a real Pro ! Many "mechanics" these days make fixing cars really troublesome...Thank God for guys like you that are real Pro's and allso are generous with us help seekers and post issue fix videos on KZbin . God Bless you and Hello from Romania in 2019. I have same issue with 2002 Toyota Yaris 1.0 4cyl vvti engine . will check tomorrow about this control valve.

[@sonsabbaththarebel1443]

Dude so far you have been a great help to me can't thank you enough.

[@667NeighborOfBeast]

Thanks for this video, immediately solved my idle problem! I adjusted the valve to the max bottom and left it there. It's probably only temporary fix, but it will do the job until i buy new one.

[@jorgel.otarolam.3241]

What a master class... man. Thanks for sharing your knowledge, you help a lot of people who own a Honda. Very well explained.

[@ScannerDanner]

thanks jerry! i really appreciate the comment. let me know if there is any other lecture video you would like to view again. I'll open it up for you at no cost. BTW as a loyal customer, do you think 45 days is long enough for the streaming videos? i was thinking of increasing it

[@1DirtbikeBoy]

just got my first honda and it does the loopy idle thing. im gonna give this a shot, thanks man you've earned a new subscriber !!!!!!

[@cloudcloud1204]

This fix worked for me. Turned out my diaphragm was backed almost completely out in the valve. Was difficult to screw in. Used a quarter instead of a flat head. Worked great

[@ScannerDanner]

sweet! thanks for watching and commenting

[@chrishouser1213]

This video is awesome. I found this problem a long time ago but the way you explain it is great. It fills in a lot of blanks.

[@ScannerDanner]

Great to hear!

[@hondothehonda4759]

@ScannerDanner great video you’re very educated I love your video, first one I’ve seen but am impressed with the amount of knowledge you give people instead of just summarizing the problem🙏🏼🙌🏻👊🏻

[@kristopherbell9885]

Excellent! learned so much here! Thanks Paul! Great explaination and investigation! Its not just hondas, this happened to my suzuki g16b motor from a baleno

[@tlk8927]

My 1989 Honda Accord is surging like this. i'm going to try some of the things you show in this video.

[@shameelali2549]

Great detail with the trouble shooting also good to see exactly why the injectors we're shutting off :)

[@anthonyjarosz3444]

Best vid out there had this problem forwver thought i would never fix it thank you so much props to u best vid ever

[@holton345]

This is my specific issue, on a 2001 Accord Value Package (like a pimped out DX - not exciting, but hey, almost nothing fancy to break over time). It has the F23A5 non-VTEC engine and the surge is *identical* to this. I was about to swap out the electronic IAC but will look at the Cold Fast Idle Valve tomorrow. I will also look for any obvious vacuum leaks. Not ruling anything out at this point, but am glad you gave me several things to put at the top of my list. Thanks!

[@bushmaster2936]

Very well done : ) Thanks for backing up ETCG's results. I now subscribe to both of you : )

[@EKLEKTE_KURIA1]

Also make sure to check your throttle body gasket as well! They will break overtime and cause it to have a vacuum leak

[@omarG19100]

had rhis issue this week . i cleaned out pirts with csrb cleaner and it fixed it. but good to know the adjuster is there in case it decides to come back. good work.

[@faustogonzalez8397]

Paul, Outstanding video AGAIN !! Keep up the great work. Pete

[@timmyoshaunessy1518]

You are definitely the best. You not only experience but to be honest I give you a A plus for knowledge

[@xerxes456]

Hello scannerdanner I also bought your great book, Ericthecarguy helped me find you and I have watching he's video same problem and he also turned the nut to bottom and now you learned me to diagnose this problem. You are the best teacher I ever seen and great personality easy to listen to. can watch your videos for hours never bored thanks man.

[@brads1234]

I usually never do this but thank you scannerdanner, after watching this video and having it all explained out, you helped correct my idle issue on my integra. Thank you!!!

[@ScannerDanner]

Thanks so much! If you need help in the future. Post here: It is becoming more and more difficult to answer questions here. I have 80,000 people asking me for help now. So I have created a forum to help you guys better. It is free to join and we can exchange pictures, wiring diagrams and waveforms if needed to help guide you through the process of troubleshooting your vehicle. Thank you so much! Hope to see you there. Paul Danner (ScannerDanner) www.scannerdanner.com/forum/post-your-repair-questions-here.html

[@roadworthy6901]

You can actually hear it without undoing a bolt, especially with aftermarket air intakes, sounds like a massive vacuum leak! Great video, this should be shared on all those awesome Honda forums.

[@jayrist7040]

loving the video, my integra has a surging idle and i think this might be my problem, i had cleaned my idle air control valve and the problem never left so hopefully this can help me tomorrow

[@timon2wheels355]

Thank you for this information. I have an Accord that has been do this since I got it. I purged cooling system, cleaned IAC but all it needed was the FITV adjustment!

[@ScannerDanner]

+tim browning sweet!

[@michaelbarlow6062]

I think you were the first one to figure out to adjust that valve all the way down👍👍

[@Pdubforever1]

awesome video. Im actually in the process with the same issue on a Honda Pilot with the exact same surging issue. I also performed the same test covering the hole to the iac valve. and made a world of a difference. So Im going in confident with replacing the iac valve. BTW, Eric the Car Guy actually has a video explaining how to turn down that adjustment It touches on the exact component you showed in the video.

[@MichaelMantion]

This is by far the most useful video on the subject. Perhaps one of the most useful videos on you tube. TY.

[@ScannerDanner]

wow! Thanks so much!

[@puppetmasterblaster]

I found it pretty worthless to be quite honest with you. A lot of extremely technical garbage that in real life had no value at all to me. In my case It was a matter of playing with Hondas ridiculously stupid throttle cables, and some bad injectors that finally solved my issues. And still have a surge only in Park. So on with my search for some actual helpful info I guess.

[@alfonsohernandez5907]

Puppet master I’m having same issue This video was informative but my integra still surging while idling when engine is hot. We’re u bale to fix the issue. Thanks

[@TheChristofear]

Have the same surging issue but on a Mazda B2200 1993. Pretty much did what you did here except you can adjust the IACV without taking anything apart by just adjusting a screw on the outside, it runs so much smoother now. I have been trying to fix this surging issue for almost a month now and my next step was a new IACV which runs between $300-$500 new. Thanks for the video!

[@bentan4334]

I should have seen this video before I decided to do overhaul on my engine Acura Integra damn.. you rock buddy!!! very helpful video ever...

[@jHuff-dm7lz]

Hello ScannerDanner, I just went through the new Section 20 of the E-Book (Engine Performance Diagnostics) Cover to cover and man, I think you nailed it. If anyone has an idle performance issue with an engine, you got the answers. I had an 05 Doge 5.7 Durango with an intermittant stall--NO ONE-- could find the fix. I did. My Friends love it when I read your books.

[@XxiBeastBoyixX]

i love full diagnostic videos! every second was filled with knowledge. keep up the good work! new subscriber!

[@ScannerDanner]

Awesome, thank you!

[@bossbaby5743]

This fixed an issue I’ve been having for months, tightened it down and works like new again! Thanks so much!

[@ScannerDanner]

Awesome

[@richardashcroft4596]

Thank you Professor Paul for this case study, I’m having this problem on my ‘03 Honda Odyssey w/3.5l engine. Following Mitchell1 DIY instructions I don’t get to radiator fan coming on point before my TCS light comes on the dash. Will be diving into your book.

[@joebourgoin6554]

Did you get it figured out?

[@gvvq-pi5ml]

Hi Paul, Eric the Car Guy had one of these valves on one of his videos, he screwed it right in then undone it about 1/4 turn and it cured hi..so think you done the right thing...I actually thought to start with when it surged it was slowing down and the IAV was opening it up to keep it running, but you proved it was the other way round..good work - Fred.

[@ieat10milesforlunch]

dude your freaking livesaver!!!!!!!!!! i finnally found out what causes my fluctuating idle!! once again thanks a lot !!!!!!

[@ScannerDanner]

thanks so much!

[@moxie-max334]

For real right here with you man I was losing my mind lol

[@PupDume]

having the same problem on an EK i just bought doing this exact same thing so tomorrow going to try this out and see what happens. Thank you

[@mixedboi]

Really nice video Paul, you deserve more attention!

[@billharding9941]

Thanks for your study. Just fixed a 1997 Honda Accord EX VTEC thanks I your instructions.

[@mingemango]

Thanks mate, I did this today and it now idles properly. Keep up the great work..!!

[@bensmokin7205]

Great video bro. Helped so much on my 96 integra ls. Hope to see more from videos from you in the future.

[@ScannerDanner]

Thanks so much!

[@joshaden6533]

This video is incredibly well done and full of great info. Thanks!

[@HighestRank]

Could have been better in focus on the scope screen but at least it wasn't fighting for autofocus.

[@xtrongarage9666]

Very educational video I learnt a lot from it and me being a Honda enthusiast. Just having a low idle issue on a H series engine that I need to fix. Pretty sure it's the Idle air control valve on the front intake that should be my issue.

[@xtrongarage9666]

IACV. Which dance for idle air control valve. That wasn't the cause of my problem it was just a dirty throttle body. Needed extremely good clean She runs like a dream now. I even made my own video on my own personal experience with this problem. If anyone's interested.😉

[@jarinwilson9539]

One thing that always bothered me on older Hondas is that the TPS is riveted to the throttle body....slightly annoying And yeah, I've ran into this exact scenario a couple of times. Another awesome video Paul

[@brett6754]

ScannerDanner you are of the few analytical thinkers out there. Thank you I have a better understanding now.. Even more than my local mechanic (^^,)

[@marianatequiero28]

Thank u sir, ur videos have been most helpful on KZbin auto,... Plez keep making

[@ScannerDanner]

+marianatequiero28 will do man. Thanks!

[@mischief.ej1]

THANK YOU , FIXED THE ISSUE ON MY 94 CIVIC

[@ScannerDanner]

thank you so much for the comment and for your support!

[@MatthewTaylor3]

This is a very good video. I wish I had all the hardware to do some testing myself

[@headsup5819]

Simple videos are always the best.

[@ScannerDanner]

For sure man, and I truly value your input on this. I am still not convinced that this seat didn't work its way loose on this one, but not sure if I will know for sure until I see more of them. And this is a dying system, so I don't expect too many more. For anyone else reading this, be careful with this "fix" and please understand the variables here.

[@inkncraig]

Excellent video Paul. I like the new editing. Will always be readying your book. What you taught me has already paid off. The

[@cincomorales]

Hi did exactly what you told me to and it work great on a 1998 honda prelude sh type 2.2 vtech engine

[@jeffreygomez7360]

Seriously I had the same issue about a year ago, it was the iacv. I’m having the same problem again n I want to blame the iacv, but it’s still kind of new. So I’m gonna check the fitv tomorrow. Thanks for the video.

[@shawnpat3ck]

Very nice video.. This might actually fix my friend's car.. Thanks!

[@ScannerDanner]

okay thanks for the feedback. let me know if there is any that you want to watch again.

[@tubejim101]

Thank you for making this video.

[@josephcole1416]

this has helped me a lot I have been trying to figure out this problem for a while now. I have a 95 civic vx 1.5 d15z I have a good cold fast idle but when the car is warmed up it surges and I have already replaced the air idle control valve and still did it so I'm gonna try this one thank you

[@wassername888]

My 99 crv does the same thing but only on cold days.

[@smurdock9500]

Thanks ScannerDanner! Was a huge help!

[@LeakyDiaper]

Haa, cool. I have an 87 Teg. Ive had for a long time so a hunting idle is nothing new to me. But I did learn something new about the injectors shutting off. It was cool to see someone actually go through a diagnostic procedure with this, and see you learn something new at the same time. Nice job. I always enjoy these vids.

[@destruxxx]

Mitsibishi also has the same issue on their pre DBW engines. I fixed many Eclipse engines that had either a FITV that fell apart internally or an ISC stepper motor with a dead winding that resulted in an idle bounce. What's worse on the Mitsubishi though is that their closed throttle position switch is an external contact switch and it can get stuck in the closed throttle position and leave the idle rev limit engaged... leaving the engine stuck below 1800 rpm and unresponsive to the throttle. Had a few tow ins over the years where they froze in the winter and by time the car got into the shop it thawed and was working again. Usually got water in from a missing rubber cover on the switch.

[@ScannerDanner]

Thanks for the tip. I think as long as the engine doesn't stall or give you any driveability issues when cold, then do we really care if the cold fast idle isn't to spec? As long as it is not too high of an RPM then I really don't care at all. If it is a paying customers car, let them know what you did and any future issues that the valve will need to be replaced. I still like the fix. Thanks again

[@mctobbsi]

Thank you! Ofcourse the main point is the injectors shuting down and I'm sure you are right! Probably the pcm also wants to see a vehicle speed signal for it to go in coasting fuel cut off and I didn't think of that before so my bad on this one! Thanks again for all you effort in making this videos!

[@ScannerDanner]

thank you my friend!

[@carlosmartinez-ij7vf]

I've had this problem for the past week and I hope this will fix my car or if it's the throttle body gasket

[@ScannerDanner]

no problem at all my friend. it is still up for debate as to why this method of control is used, but at least we know for sure now what is causing the surging.

[@ScannerDanner]

sweet man, thanks for the tip. makes me feel better about what I did in the video.

[@cbobcbob100]

Dan....another great video......About a year or two ago I believe that ERIC THE CAR GUY did a video on this valve,.....might be worth a look....thanks again.....bob

[@davidtruckcoe7064]

good show thanks my 1995 idle high but smooth takes over 10 minutes to lower to 725 rpm .i live in a cold rainy place 27 days rain in march

[@tinydx95t2]

I love your videos.They are very informative!

[@ScannerDanner]

I like the comments and feedback! Keep them coming. I looks as though valve replacement would have been the proper fix hear. I will update this in a few months and let you guys know how our "fix" is doing, as this car is owned by one of our students.

[@indigo_dreamz]

Any updates please 🙏

[@ScannerDanner]

@piksylicious from 9 years ago but yes, this was a fix 😉

[@leeoshea2290]

@@ScannerDanner I have a 2004 honda jazz, in Australia. The IACV under and attached to the throttle body is water/coolant , magnetic, electronic (it plugs in), the spindle was seized hard. It took 3 days of soaking with carby cleaner, squirts of wd40 and ,eventually, a firm but gentle twist with pliers to start moving the spindle that appears to be magnetically controlled too, (what a pffft idea). So, the engine would idle fine at start up. Once warn/running temperature, the idle would fluctuate between 900 & 3,300. crazy. After repairing the IACV, the idle has been good for about 4 weeks. 1.5 l 5sp manual idle @ 750. well, yesterday the erratic idle restarted. With all the variables of possibilities it could be any of a dozen things. Think I'll start with cold idle valve adjustment. 2nd will be the IACV again (apparently if replacing, it has to be oem or the computer won't recognise it, what a pita). A new part here is over $900, about $550-$650 US depending on the day. Lots of 2nd hand refurbished? parts, don't trust those. It comes to a point when the parts to fix these cars are way more expensive than what the car is worth. It's a shame. When they run well, they are good cars. When they don't, well, bonfire night looks good. Thanks for the in depth analysis you have provided. Hopefully, at some point, this offset idle can be sorted for a reasonable cost. Mechanics here are way too expensive, as in, they want money even if they can't fix it. I don't mind paying labor costs, that's business, but, $1,000 or more for a non repair, supposedly diagnosing with no fix, I'll stick to you tube and try and try again until victory

[@carslover3509]

very very very great information i have Mazda 323 its have high idle and i did every thing i know but its same just now i know the cause thanks very thanks for great videos

[@rehlek]

ScannerDanner i've had quite a few hondas with this exact same issue, and ive had great success on disassembing the valve and cleaning it out with carb cleaner or brake clean, and reinstalling. after that it worked perfectly everytime with no adjustments required. just for future reference maybe give that a shot.

[@mrceej]

Good video, very in depth.

[@ribak1983]

thanks! fixed 95 civic ex,now it runs like it should

[@angelramirez7747]

Scannerdanner you are 'THE MAN'! Me and my neighbor were diagnosing an idle issue on a 97 honda accord. After watching your video it took 5 minutes to determine the cold fast idle valve was the culprit and 20 minutes for the repair. Thanks for the great content scannerdanner!

[@YouTube.TOM.A]

Your work is greatly appreciated. I think that the cold idle unit fails [degrades] sometimes like a thermostat fails. It is a thermostat certainly, with wax and a plunger in a sealed chamber. after many oscillations the plunger develops small leak against the cylinder walls,so the wax pressure may not be as forceful. I am guessing that is why when you close-in the passage you still have some plunger movement but not the ideal stroke distance. the internal spring forces the piston back on cooling

[@joshuasummers7242]

love your videos scannerdanner, help me learn alot, i hope you read this, those fitvalves are adjustable that brass ring you can turn in or out, i know they have a problem with them working themselves out and causing same symptoms , i did scope test before and after i adjusted the valve in and was a good fix just by adjusting the brass ring in, no need to replace, please get back to me and confirm, ive done on 2 different cars and no problems, without replacement, id id love for you to test this fix100% so i know for future

[@jdmjuan661]

dude i have had this problem happen a 2nd time but forgot what j did to resolve the issue thanks alot

[@micbanand]

Just wonna thank you! I'm a multiman. know alot of everything. why because I just love to do things myself. Why is it so easy. to be very good at stof. Because of People like YOU. Thanks

[@ScannerDanner]

an honestly, the other HUGE problem in my field is most "professional mechanics" are parts changers and cannot do proper troubleshooting

[@tmanda323]

In my country the bigest problem is a lack of knowledge, a lack of information, without desire for learning....that's why most of professional mechanics are part changers

[@ScannerDanner]

@@tmanda323 where are you from my friend?

[@tmanda323]

@@ScannerDanner Serbia. Europe. I have your e book.

[@ScannerDanner]

@@tmanda323 Thank you! Armed with that, you can be one of the ones in your country to change things!

[@MarioHernandez-xp6vp]

I'm a part changer but just bc I don't want to go to a mechanic. Changed ny MAP sensor. And my TBS. Now I'm here to see a professional at work.

[@ScannerDanner]

thanks man, i will for sure

[@GRowe1978]

I've had a couple of Volkswagens do the same thing. In both cases, it was the coolant temp sensor.

[@Writz1995]

Adjusting the TPS until idling smootly solved the same problem. Maybe the surface of the TPS's resistor is worn, and needed to be adjusted slightly. It's running for a few days now like a dream. Hope it helps.

[@ScannerDanner]

thanks for the tip!

[@khrisjared1]

This is awesome. Good job. I will try to work on my honda accord 2000 V6. I only have problem with the idle surge during cold start especially in the morning. After I started my car idle fluctuate but once it warmed up it goes back to normal idling. And I had never encountered this during summer time. Hopefully this will help me from your videos... Thank you very much. I will try to post it if this will fix the problem.

[@ScannerDanner]

+khris jared first thing, make sure your coolant level is full, second is look for any obvious vacuum leaks

[@dianag888]

Did you find out what it was

[@mash33261]

i realy admire your work and thank you for the tip

[@jacoblahr]

I drive a 95 honda accord and it just started doing this bullshit. Thanks for the info i just went and checked under my hood for that cold fast idle valve and its there. I know what i gotta do now👍

[@IAutoEnthusiast]

Love your TS & R VIDEOS

[@younismark]

Again another great video, Please keep this great video going, it is really helpful,...Specially i am studying Automotive Technology.

[@JoelAutomotiveInaction]

Thank you, for posting other good video good job showing us this method.

[@nottyvondutchmusic2354]

I've had those valves back out on me quite a few times. Snug em up, and it usually solves the issue.

[@ScannerDanner]

yep, it is your main input for engine load and has the biggest effect on fuel delivery

[@ScannerDanner]

makes sense for sure, so if this is the case with this one, all I did was put a band-aid on it. Do you think the seat could have moved? It turned pretty easy on this one.