Erratic idle???

DKW 86DKW 86 Band Wagon
in Engine & Drivetrain
89 Civic Wagon DX 5MT.

The idle will fluctuate between 800-3000rpm in completely random pattern.
Checked for any vacuum leaks, found none.

Idle Air Control Motor?

Comments

  • NZ-DB8RNZ-DB8R Moderator
    Id check the IACV, clean it out with some carb cleaner and compressed air.
  • humorwvphumorwvp Wagonist
    Also after you clean it and replace it reset the ecu by pulling the hazard and ecu fuse for about ten seconds. In some cases you may have to go through the steps to reteach your ecu proper idle.
  • DKW 86DKW 86 Band Wagon
    Thanks guys, got my am project lined up now.
  • JDMWago666JDMWago666 Senior Wagonist
    Check for air pockets in the cooling system. Bleed it cold and hot. This happened with an Integra I was working on and it had more than a few air pockets in the cooling system. Once you get the air pockets out it should help
  • geezfoolsgeezfools Wagonist
    I just did the IACV a couple nights ago. That thing was filthy. Sprayed the hell out of it with carb cleaner and cleaned it up as best I could. Got it back on and then it would die instead of idle. Unhooked the battery for 15 minutes, better, but not great. Drove home and parked it. Next morning it was ten times better, like a new car. Went ahead and bled the coolant and now it runs like a dream. Worth a check for sure :)
  • DKW 86DKW 86 Band Wagon
    The IACV is cleaned and running much better.
    Worked at an auto parts chain store the last 18 years. The PGMFI will need to program itself after the IACV clean, expect at least 20-30 minutes of drive time before that happens.We have changed out batteries and not used the ECM Saver and had them not start. The PGMFI on most cars remembers and adapts to the dirty IACVs. The new battery will reset it to default and then suddenly it wont crank. On the other hand, if you clean them, the old settings are still in there. Just expect an adjustment time. Mine was cool in about 10 minutes.
  • geezfoolsgeezfools Wagonist
    even driving didn't help my car, I didn't notice a difference until it sat overnight. I love going out to my car in the mornings and just turning my key, rather than having to hold the gas for the first ten seconds :)
  • DKW 86DKW 86 Band Wagon
    My 89 1.5L 5spd DX still has an erratic idle, 800-3000 rpm. It also has a random hard start condition that seems to be worse when hot as well.

    Cleaned the IACV 2X and it seemed to do better.
    Finally got a new Standard AC190 and put it on yesterday.

    No change at all.
    Do i need to reset my ECU?
    i get a random check engine light too and just found out how to read that. But it resets if i turn the key off, is that right?

    At my wit's end. May take it to the Honda Shop in town this week.

    Thanks in advance...
  • geezfoolsgeezfools Wagonist
    you do need to reset the ECU from what I understand. Mine sitting overnight fixed the issues I had though without physically doing anything. You will probably need to bleed the coolant system as well. Sounds like it could be something else at this point though, I'm out of personal experiences.
  • DKW 86DKW 86 Band Wagon
    Pulled all the fuses under hood. No difference.
    How does the air bubble thing work as far as idle goes?
  • WagoDanWagoDan Wagonist
    Coolant flows through Idle motor and has a tendancy to trap a bubble as it is a "side note" on the flow of the system, not directly in-line that is. The temperature is what the motor adjusts itself to, if a hot air pocket hits it then motor adjusts then back again when coolant get there.
  • darktricksterdarktrickster Wagonist
    the random no start is probably your Main relay. as far as the idle problem, try adjusting your idle. It's a screw under the black box that has PGFI written on it. it will be to the left of the throttle body if you are looking at the engine from the front and there may be a little black piece of rubber covering it (remove it if there is). you can just barely get a flathead screwdriver on it without removing anything(it will be at an angle so be careful not to strip it). Usually have to turn the idle down. Also, when it decides not to start, bang the dash an inch or so above the hood latch a few times and see if that gets it going. If it does, it is definitely the main relay causing the no start problem. They are easy to fix, just do a google search or pm me.
  • jpciiijpciii familEE
    the idle surging up to 3k and back down is classic IACV problem. If you've cleaned it out, you may still have air trapped in its coolant passage. You could try to "burp" the system by removing the proper coolant hose that attaches to the IACV for a second while the engine is running... can't remember which hose is in and which is out. Sometimes just driving it and running it through a few heat cycles gets the air out.

    Another thing you can do is choke off the air going to the IACV. For the dpfi setup, there is an air hose from the air box on top of the throttle body that runs down to the intake manifold next to the IACV. Pull the hose off the air box and cover the end of the hose with your thumb. You'll probably feel suction and your idle should calm down. If you pop your thumb on and off the hose a few times, you might be able to get the spring and plunger to loosen up and behave... that's worked for me before, anyway.
  • DKW 86DKW 86 Band Wagon
    Finally caught the code and pulled it. It said #6 Coolant Temperature Sender.

    We are replacing it and see what happens.

    Burped the engine three times really well, still erratic idle when warm.
  • darktricksterdarktrickster Wagonist
    adjust the idle, Always works for me after I try everything else.
  • spede18spede18 Wagonist
    My TPS sensor was the cause in similar situation.
    I could pull the plastic connector off without having to press down the release for it.
    Replaced that and idle problem solved.
    As stated also check your IACV and replace the gasket.

    Good luck!
  • DKW 86DKW 86 Band Wagon
    New IACV.
    The Honda Mechanic finally saw the code.
    #6, read it as Coolant Temperature Sensor.
  • geezfoolsgeezfools Wagonist
    So it's better now?
  • DKW 86DKW 86 Band Wagon
    Wont get it back till Monday some time.
    The Diagnoses came late late Friday afternoon and i was out of town all day Saturday.
  • DKW 86DKW 86 Band Wagon
    The CTS seems to have done the trick.
    Idle is smooth as ever. Now on to greater things.
    Brakes, Front End Parts, Paint.
  • tpar1220tpar1220 Band Wagon
    does the 87 1.5 with carb have this idle control motor thingy as well?
  • DKW 86DKW 86 Band Wagon
    952.jpg
    Yes, supposed to look like this according to Advance Auto Parts website.
    http://shop.advanceautoparts.com/webapp/wcs/stores/servlet/product_idle-air-control-valve-bwd-intermotor_18481051-p?navigationPath=L1*14932%7CL2*14985%7CL3*15349
  • tpar1220tpar1220 Band Wagon
    ok.. thank you sir. now i just need to figure out where it's located.
  • MiXMiX Band Wagon
    Oh, just a heads up since I've been researching this as well. A lot of people have found that the PCV valve and/or breather can cause this kind of issue. It's worth checking just to be safe. I found that the PCV valve is usually just a couple bucks to replace, and the breather chamber can be flushed with old gasoline a few times, then left in the sun all day to evaporate. Just like this. I'm going to give it a try once I finish rebuilding my engine.

    If not to help you, hopefully this clues in someone else searching the forums later. :D

    Best of luck!!
  • tpar1220tpar1220 Band Wagon
    DKW 86 wrote: »
    952.jpg
    Yes, supposed to look like this according to Advance Auto Parts website.
    http://shop.advanceautoparts.com/webapp/wcs/stores/servlet/product_idle-air-control-valve-bwd-intermotor_18481051-p?navigationPath=L1*14932%7CL2*14985%7CL3*15349


    huh, kind of confusing. that link brings me to fuel injection parts? my 87 has the 3 barrel carb, do the carbed engines have this iac thing?
  • DKW 86DKW 86 Band Wagon
    Yes, this is the one for the 1.5L Carb car.
  • tpar1220tpar1220 Band Wagon
    i never did find the contraption pictured above.. i did change my radiator though from the small to a new large. the small cooled fine till i hit interstate then it would run at about 3/4. once off interstate, even in bumper to bumper traffic it would run bout 1/4. anyway.... after the swap.... no more erratic idle. it idles smooth as silk, so i assume i had a pocket of air in cooling system..
  • toys-n-joystoys-n-joys Wagonist
    tpar1220 wrote: »
    i never did find the contraption pictured above.. i did change my radiator though from the small to a new large. the small cooled fine till i hit interstate then it would run at about 3/4. once off interstate, even in bumper to bumper traffic it would run bout 1/4. anyway.... after the swap.... no more erratic idle. it idles smooth as silk, so i assume i had a pocket of air in cooling system..



    you have a fitv on your throttlebody and a iacv on your intake manifold in the back with coolant lines running to it. if its a carb model im not sure.



    a small bubble in the coolant can cause a idle problem. thats a typical honda problem. its hard to bleed it properly without a incline.
  • tpar1220tpar1220 Band Wagon
    toys-n-joys wrote: »
    you have a fitv on your throttlebody and a iacv on your intake manifold in the back with coolant lines running to it. if its a carb model im not sure.



    a small bubble in the coolant can cause a idle problem. thats a typical honda problem. its hard to bleed it properly without a incline.


    it is a 3 barrel carb... and i am not sure either, but long as it keeps running smooth i am not gonna worry bout it to much cuz it is a pain to work on with all those vacuum lines all over the place. even removing the breather is very unpleasant.
Sign In or Register to comment.

© Vanilla Keystone Theme 2025