Hey new member to the site, hopefully I can get some help on my issue. All work to the car was done by a friend of mine who previously owned the car before me, but I will try to add as much description as possible to what the issue is. The car is a honda civic dx hatch, 1999, 5spd, D16Y7, Y7 throttle body, Skunk 2 intake manifold. The car ran fine before the skunk 2 intake manifold was installed. Once the skunk 2 manifold was installed the car has the issue where the idle jumps from 1000 rpm's to as high as 2000 rpm's. If I start the car and let it idle it will eventually calm down and idle at 1000 rpm's but when I start to drive it will do it from time to time when I push in the clutch or am sitting in neutral. Other times is will just act normal like it should.

Now I am getting an error code, after resetting the computer that come on anywhere from 40-60 miles for idle air control failure. Despite the code the code I have a few new IAC's and the one in the car is new as well.

Also sometimes when the light is on the idle jumps rapidly up and down and when the scanner is on it and im looking at the live data it is jumping between open and close loop. This causes it to rocket and drop from 1000 to 2000 rpm's very rapidly. Only sometimes does it violently jump idle like this.

Things tried:
-I have tried doing the 3 wire to 2 wire connection, all unpinning and repining of the connectors and the computer were done correctly, This I made sure of, plus I double and triple checked as well, this did not work. Further research turned up that even though the fix was done the computer is only looking for one specific connection whether it is suppose to be the two wire or the 3 wire. So doing the connection fixed nothing.
-I tried swapping out the computer for a different computer. This gave me a code for VTEC failure because obviously there is no VTEC present on the car, this also made the car jump idle violently and corrected nothing.
-Did some more research and found another possible fix. I tried taking the IAC and leaving it connected to the TB, then plugging in another IAC to make it appear a connection was still being made, this did nothing.
-For a long shot I tried taking and putting a spacer on the map to read less air for the hell of it, as I suspected it did not work.

Im not a fan of skunk 2 products and it is very apparent why the Y8 mani swap is so popular but if I can make it work I will keep it because of some future plans with the car. one Idea I have is that the Y7 TB just does not mesh well with the intake manifold and is causing this issue, so it would be better to use the Y8 TB. Unfortunately I do not have a Y8 TB to test this theory and buying one for testing purposes is not exactly a good idea imo. The other thing I have been told to work is to take and make a block off plate for where the IAC goes on the TB. Put the block plate on the TB and leave the IAC plugged into the lines and it should stop the wild idle and take care of the light. Out of what I have tried I feel that may be the next step, but yet I am still skeptical about this.

I do have the stock intake manifold and if I can not get it corrected I will be putting it back on. Not to mention I do not like just giving up on things without first exhausting all options. If anyone has any input, or anything to try I would like to hear it. Sorry for the novel here but I like to get to the point and add in as much info as I can since we all know that makes quite a difference in trouble shooting an issue. Thanks for reading.

 

You can only use the 3 wire IACV with the Y7 ECU. Swap everything back to the 3 wire setup first.

 

The same day I was doing all the testing I set everything back to the 3 wire set up since the 2 wire was not going to work with the current ecu

 

be sure you're using a Y7 TB gasket. the other TB gaskets will allow a leak in this area causing the irregular idle.

 

Yes the TB gasket is the Y7 gasket. The only thing about the Y7 TB is it looks like some of the TB gets blocked when it comes together with the Intake manifold, thats where the idea for the Y8 TB might work better, but I just dont have one to test the theory.