Honda Accord 2000 revs up and down in neutral or parking
 

Hello guys! I'm new here. Its really nice to be here.
I have this problem on my Honda Accord 2000 VTEC 2.3i Automatic Transmission. I had an engine swap couple of months ago after which I started experiencing terrible rough idle. I'm from Nigeria, our mechanics here does not have much experience on how to tackle electrical problems. So they manually adjusted the idle screw located above the throttle body. Even with the adjustment the idle was rough when I on AC or when in gear even with head lights on. By following some threads on this site I finally realized it was my iacv all along, so I had a new one just 3 days back. When I started the car after the iacv was installed, the car revs very high about 2500rpm or so, which was expected I guess due to the screw adjustment. So the mechanic drove the idle screw all the way in but could not get the idle to drop below 2000rpm. So he decided to block the iacv air intake located in the TB right before the TB plate to stop the air flow and drop the rev, which works. When I get back home as i knew what he did was not proper, I unblocked the iacv air flow and the rev went back up 2000rpm. After doing some checks for vacuum leak I found that the TB plate was not closing, there's little air coming through from within, so i tried and was able to get it to close properly. Just after I did that the rev starts to go up and down between 1200 - 1800rpm and when I take off the iacv harness wire it revs between 1000 - 1200rpm very quickly. I checked there was no vacuum leak on the intake manifold because when I stick my finger and block the air flow hole right before the TB plate, the car stalls. At start the car will rev at about 1100rpm without any problem, but when I on AC or shift gear or step on the gas pedal or apply any load to the engine, the rev jumps up and then start surging up and down. I also tried doing the DIY idle learn thing by adjusting the idle screw and removing the battery but I couldn't get it to drop to the base idle of 500-550rpm or so. Please help.

Sorry for the long unnecessary story, I was just trying to be as detailed as possible.

Thank you.

After changing the IACV, did you bleed air out of the thermostat housing? Honda idle-control system gets confused if there's air circulating in with the coolant.

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Yeah I bled the thermostat and there was no air pockets. I did it by opening the radiator cap and let the engine run for about 15mins.

You still have air if that's the way you bled the system. Did you squeeze the hose back and forth while the top was open or you just let it sit. Follow bleeding procedures to make sure.

Also how did you get the TB to close? What was the temp there? I don't know about forcing it to close. You TB should never be closed all the way at idle.

No I did not squeez anything. I read that the TB should close completely at idle and the iacv take over the control of air flow. On the rorataing part of the TB, when younpull and release the throttle cable, there's one curvy metal that sits against part of the TB which stops the plate from closing all the way (it make click sound as it rests against the TB body). So I noticed that and I pulled it away from the TB on which it rests so that it goes beyond that threshold and the plates closes. The temp here is around 22 - 24 deg.

Hope you understand.

If you are sure that all air, the idle air seal is clean and makes a good deal then do a idle relearn by starting the car and keep the rev at 3k for 10s. Then let it warm normally. If this does not work it could be a faulty IACV.

Are you getting a p0505 or any codes? Was it a new valve installed.

I did the relearn procedure multiple times but it didn't work. I have check engine light on and maintenance light is on too. The iacv is not brand new. The surging started right after I close the TB completely at idle. I bled the thermostat the proper way but still having the problem. I realized it surge when the engine is warm.

Undo the what you did to the TB. I might be wrong but it's not supposed to be closed at idle. It will strangle the engine. See if the surge stops. You might be looking at a faulty valve.

Also do you have a reader to read the codes?

Okay I'll undo it, but the idle will probably go high. I'm out of town now, when I get back I'll try that.
No I don't have reader but I'll take it to a nearby car dealer and have it diagnosed.
Before the iacv was replaced, I had the car diagnosed and the codes retrieved was MAP and oxegen sensor and I had both replaced to no avail.

Thank you for your help I really appreciate it.

I'll let you know what happened.