K24a2 swap - Hunting Idle Issue

I have a 2003 Civic Si with a K24a2 swap with the RBB manifold that came with the EP3. My issue is that the car is "hunting" at idle. when I let off the gas, it will pause around 1500 rpm for about 5-10 second then drop down to the designated 900 rpm.

I have tried the following solutions:

- Cleaning the IACV and ensuring that it spins
- Removing the IACV and installing a Karcepts Block off plate (w/ kpro of course)
- Burping the coolant system (successfully)
- Checked for vacuum leaks (couldn't find any)
- Installed a new O2 sensor (not the issue but thought I should mention it)


One thing I should note is that a code came on for the ELD but I disabled it in Kpro long before this issue arose (about 8-9 months before). Also, the car is burning oil but I am assuming that is due to valve seals and/or piston rings because the head gasket was replaced last year. I have not performed a leak down test yet but will do so before I pull the motor to install the new valve seals and other seals/gaskets.

I have been looking this issue up for quite some time now and still cannot find a solution. I am beyond frustrated to the point of selling the car. Please let me know if you have any ideas or suggestions. Thanks in advance!

Have you adjusted the "Idle Valve Duty Cycle" in Kpro? If not, try that.

I did that when I had the IACV installed on the car. It seemed to help a bit but it ended up just messing with the idle and not the hunting issue. Thanks for the reply!

Correction: I am running a PRB(EP3) manifold not a RBB.

had a similar issue with my k20a swap.
i found the throttle cable was being "kinked" and would act just as you described.
i got a throttle cable from a 96 civic dx. it isnt the same length as the ep3 and i was able to run it straight to the throttle body... i used zip ties to hang it....... and BAM success.

your already up on the game with the k24a2.....fix that "little" throttle issue and keep that awesome car.

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Originally Posted by mussh

had a similar issue with my k20a swap.
i found the throttle cable was being "kinked" and would act just as you described.
i got a throttle cable from a 96 civic dx. it isnt the same length as the ep3 and i was able to run it straight to the throttle body... i used zip ties to hang it....... and BAM success.

your already up on the game with the k24a2.....fix that "little" throttle issue and keep that awesome car.

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Thank you so much for your response! I will try this when I get off of work today and let you know how it goes!

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Originally Posted by OneDayTypeR

Thank you so much for your response! I will try this when I get off of work today and let you know how it goes!

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my "kink" was due to the mount on the intake.
try unclipping your throttle cable from that mount and give it a rev.......... if it drops to normal right away....you found the issue!

good luck!

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Originally Posted by OneDayTypeR

I am beyond frustrated to the point of selling the car. Please let me know if you have any ideas or suggestions. Thanks in advance!

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Okay first I have to say that I have a total lack of understanding for anyone of this attitude, honestly you need a new hobby if you feel this way, get a bicycle or take public transport but if you get frustrated enough to sell a car with that simple a problem then you should honestly not own one, especially a modified one. I would never sell my ep3., I would never even think of it.

That said you have either a vacuum leak or a control solenoid is busted or something that's allowing air in, f it was the iacv obviously something would have happened when you used the block off. So air is getting in, check your purge valve and your "intake air bypass thermal control"

just out of curiosity.....any luck?

Bump for an update more solutions people find easier to search ;)

I have the PRB intake on my k24a2 which means you don't have the Air Assist Valve. So is it hunting on start up? It cant be running that well if your IACV is blocked off? I'd keep looking for vacuum leaks.

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Originally Posted by captaingamez

Okay first I have to say that I have a total lack of understanding for anyone of this attitude, honestly you need a new hobby if you feel this way, get a bicycle or take public transport but if you get frustrated enough to sell a car with that simple a problem then you should honestly not own one, especially a modified one. I would never sell my ep3., I would never even think of it.

That said you have either a vacuum leak or a control solenoid is busted or something that's allowing air in, f it was the iacv obviously something would have happened when you used the block off. So air is getting in, check your purge valve and your "intake air bypass thermal control"

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Hey guys, sorry for taking so long to reply. I have been really busy and haven't had much time to get online or mess with the EP.

Captaingamez I purchased this vehicle in order to fix it and make it a respectable daily. When I got it it had no A/C(fixed), Check Engine light was on(fixed), Water temp gauge didn't work(fixed), and many other problems. I have been constantly fixing this car while driving it to college on a daily basis. I have always worked on cars and will continue to do so, but I am now a working professional and cannot afford to have my daily break down on me. I do not want to put anymore money into this car because I will be building a Lexus SC400 for track purposes(road race). This is my reason for wanting to sell the EP3 so I hope you can respect it.

Sorry for the rant guys, since my last post I have messed with the throttle cable, and reinstalled the IACV but rerouted the coolant lines so they aren't connected to the TB anymore. I figured this would make it easier to remove the TB for future purposes. However a check engine light came on for a faulty thermostat which was just recently replaced. I did burp the system for a good 20 minutes and kept filling it up. I doubt the rerouted lines had anything to do with it because the coolant only heats up the air entering the TB and goes back to the same location anyways. I will mess with this more later. The car is still hunting for idle so I am going to try and spray some TB cleaner around the TB vacuum lines and manifold to see if there is a spike in RPM. I will try to work on it Thursday and give you guys an update. Thanks again for all of your help and support!

I still think this may be ecu related. Have you tried a different calibration? Also, did you setup/scale your TPS in Kpro?

i had a similar thing like this. i found when i went into my hondata and change some of the settings in the idc valve it seem to fix it. good luck