Hello to all. So Im working on a 89 accord lsi, 200000+ miles, I installed a yard engine do to a knock. everything was great for @ 6 months. A few weeks ago the idle started surging. Found this sight and did some research. this is what Ived done so far: cleaned the IACV and FITV per instructions on thi sight. Cleared codes by disconnecting bat for 30 minutes. made sure coolant level was correct and bled, sprayed carb cleaner on all vacuum connections with no change in idle. When I got it all back together it idled great until warm. then started surging again and is doing all the time now. My wife drove it to town the other day and the check eng light came on turned off, then came on and stayed on. Checked blinky light under seat and its blinking 12 times. SO HELP PLEASE, Thanks Rob

 

You can grab a PDF copy of the service manual from here:
http://www.pauldesign.ru/honda/shopmanual.html
(made sure you download the core manual and the '89 supplement)

You should be able to find out from there what the 12-blinks means.

The last time I had an idle surge on a Honda motor, it was because the throttle body wasn't entirely closing all the way when i was off throttle. I could move the intake tube out of the way exposing the butterfly in the TB and push on the bottom to close it. It wouldn't really noticeably move, but the idle would go back to normal. Then if I tapped the throttle, it would go back to the idle surging. I guess it was just gummed up so it was sticking instead of closing all the way.