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Does the IACV play a part in Fast Idle warmup?

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  • HondaFan81
    replied
    Follow my DIY sticky for base idle setup. Then, PM me if you can not get it to idle at 600 RPM base idle (with IACV disconnected), that would indicate vacuum leak. Assuming you can get to 600 base idle RPM, when you reconnect IACV...it should kick up to steady 700-800 RPM.

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  • Granite CB7
    replied
    ^Exactly, I could literally open both my shutoffs w/ the engine warm, not soon after, bouncing would stop, idle would drop. I do not understand how some are running the FITV w/ no coolant at all, I just don't, it leads to alot of headaches and the bouncing idle is just plain embarassing and annoying. It does take a really long time for the coolant to get warm enough to somewhat close the FITV, but it's still somewhat open, if I opened my valves, the idle would drop to about 5-600, which is way too low, even w/ the idle screw maxed out! That is why I had to adjust the stop set screw alittle bit, my idle has been perfect ever since, FITV is fully functional for winter and I have a good base idle and good idle for when there's a large draw-h/l's, heat, and r. defrost. But do remember that I am not running the IACV, so that is why my idle would drop so low I'm pretty sure.

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  • C91BLX7
    replied
    Personally I'd leave the coolant lines to the IAC and make a block off for the fast idle

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  • foamypirate
    replied
    Granite, you seem dead on with my thinking. I was pondering at work today, and it crossed my mind that since the FITV is still full of residual coolant, and is not being heated up as it normally would, that it is causing the bouncing idle until it finally gets enough radiant and conductive heat transfer from the IM to warm it up enough to stop acting on the idle.

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  • Granite CB7
    replied
    ABV is probably best removed IMO. I had alot of trouble w/ my FITV on my H/A6 IM. I put brass shutoff valves up and down stream from the FITV to allow it to function, but keep the t/b and plenum cooler. It took forever for the FITV to fully close since it wasn't seeing much heat, when it was partially warmed up, it would idle bounce horribly. IACV is blocked off and has been for a long time.

    Right now I have the 2 valves opened for the FITV, idle screw is not maxed out, about 1/2 way out, and the stop screw for the throttle rotor was bumped up alittle bit to raise the idle more, the idle screw wasn't able to raise it enough.

    Next summer I will turn the valves off and put a piece of metal repair tape over the inlet hole on the t/b's bore, then the motor will have a set base idle cold and warm, since it's summer, it won't matter.

    Oh, also, not having coolant going through the t/b is fine, on my old A6 IM, the butterfly NEVER stuck once even @ below 0F temps. It's all in how the stop screw is set, if it's not high enough, it'll stick all the time regardless of temp.

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  • bcjammerx
    replied
    pretty sure both of mine are d/c'd.

    The fitv reads the cold temp and may idle up but only when it's REALLY cold (40 and below). Once the engine warms up, well then the head warms the fitv from radiant heat and from transfer so it won't rev it up. Mine only revs to 1000 at best, then 700 afterwards.

    Right now my car won't idle up on cold starts...and almost bogs down and dies when it's cold and I come off the gas.

    I need to hook the lines back to the fitv to get the 1500 cold start idle, and I need to enlarge the holes on my custom iacv gasket...should solve my problems. not sure if that helps you any.

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  • 19dabeast85
    replied
    Just because the coolant lines are removed from the FITV does not mean it will necessarily work properly. A bouncing cold-start idle is 95% of the time due to a bad FITV. It could also be your air boost valve malfunctioning but less likely there. There's a test procedure somewhere on this site for diagnosing a jumpy idle that tells you how to check the FITV, but I'd have to do a bit of searching to find it....

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  • baracuda
    replied
    hook it up its not staying 75 for long. hell i think i didnt get out of the 60's today. wait a month or 2 and it will warm up and you can disconnect it, since when you start it in the AM it will be like 95 lol.

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  • foamypirate
    replied
    Originally posted by Sarthos View Post
    would removing the coolant lines to the intake manifold help keep it cool? Or would that be bad during the winter?
    You only really want to disconnect the FITV, as the other coolant ports feed to/from the cylinder head. Removing the FITV is not recommended in colder climates, as it helps prevent the throttle butterfly from sticking to the throttle body bore. However, I live in Texas, where we are still enjoying nice 75* F weather. If the idle surge continues after I try a few things, I'll probably hook the FITV back up.

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  • Sarthos
    replied
    would removing the coolant lines to the intake manifold help keep it cool? Or would that be bad during the winter?

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  • Pazzword JDM
    replied
    Originally posted by foamypirate View Post
    No, still haven't had a chance to drive the same route yet. I want to keep the results as consistent as possible.

    I would reconnect the FITV, but I'm trying to eliminate as many sources of heat from the IM as possible.
    im guessing you dont live somewhere cold, otherwise you wouldnt be eliminating heat sources. you may have to connect the FITV.

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  • foamypirate
    replied
    Originally posted by Sarthos View Post
    Connecting the FITV seems the most obvious way to fix it?

    Did you get temp reading before/after installing your gasket?
    No, still haven't had a chance to drive the same route yet. I want to keep the results as consistent as possible.

    I would reconnect the FITV, but I'm trying to eliminate as many sources of heat from the IM as possible.

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  • Sarthos
    replied
    Connecting the FITV seems the most obvious way to fix it?

    Did you get temp reading before/after installing your gasket?

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  • foamypirate
    started a topic Does the IACV play a part in Fast Idle warmup?

    Does the IACV play a part in Fast Idle warmup?

    Just curious, because I looped the lines for my FITV (it's not connected to anything) when I installed my Bisimoto intake gasket, and my car still idles higher on startup, and sometimes if I drive before it's fully warmed up, it will do the typical Accord bouncing idle, like my FITV is out of adjustment.

    So, it appears that the IACV does indeed play a part in cold start fast idle. I just need to figure out the bouncing idle now that it's doing it WITHOUT the FITV connected.
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