I have an accord w/ H22 swapped engine. My problem is about the rpm. when I release the accel pedal, the rpm drops below normal (< 500 rpm) before it is going up and stable to normal (800-900 rpm). I already replace the IACV, clean the throttle body and FITV, check the TPS voltage, but the problem still remains. I have no idea anymore about this problem. Anyone please help?

 

Check this thread about cleaning the IACV & stuff.
https://honda-tech.com/zerothread?id=1844067

In that thread, I describe how to set your BASE idle (which is not the same as the operating idle). Then reset your ECU and let it re-learn the behavior of the idle system. Have you done that process? The ECU learning the idle behavior is just as important as having clean, good parts.

 

do you have a really light flywheel?

 

Dude, I finally tracked down problem that was plaguing me for 4 years that was similar to your issue. After that long and numerous replacements of sensors and cleaning the entire engine, I found that the two screws on the throttle body were way out of whack. I never even thought about it before!

What I did to fix it and get the thing idling properly was:

Allow the engine to fully warm up, then kill it. Adjust your air bleed screw all the way in. (the big flathead screw aiming the same direction as your opening in the TB, located just to the upper left of it) Make sure it's actually screwed all the way in. It could trick you if you don't have a shorty screwdriver, by binding up and making feel like its all the way in.

Once screwed in, you need to return it to a base setting of 2.5 turns counterclockwise. Once you are there, then adjust the throttle stop screw, located underneath the throttle wheel, which is a allen head set screw held tight by a nut. Crack the nut loose, then start your car and adjust that stop screw until the idle reaches 1,200rpm. Now, retighten that nut holding the set screw.

With the car still running, go back to the air bleed screw and screw it in until the idle drops to 900 rpms, kill the car, reset the ECU by pulling the 7 amp radio backup fuse under the hood for 15 seconds and replace it. Start the car and marvel at its' innate ability to hold a freakin solid idle!

Of course, after resetting the ECU, it may want to jump back up a 100 or so rpms just from the ECU correcting itself, which will be ok. Just go out for a drive and let it do its' thing for a while, then bring it back and re-adjust the airbleed screw again if needed. You shouldn't have to reset it again after that, it will just learn the new setting over the course of a few miles.

This is a really cool fix that may very well be the answer alot of people are looking for, especially if you have an after market TB or have ever messed with those screws intentionally or unintentionally.

 

No. everything is stock. TB, Cam Shaft, Valve springs, Gear box are all stocks. Well.....I am planning to buy Skunk2 for Cam Shaft, Valve springs and cam gear, though. But I wanna fix this problem first. It's really bugging me.

 

Thanks. I will try to follow your step. Catch ya later

 

Thanks for your full explaination. Actually I already had someone (technician) cleaned those things (IACV & FITV). Even I had replaced the IACV with a new one. Maybe that guy didn't clean it thoroughly, and besides that I haven't reset the ecu yet. I will do it again from the beginning.