So I'm really thinking that I got something I need to dig into..so I have a 99 civic EX with a d16y7 bottom and a y8 head. About a month ago it popped a code for P0505 which is IACV. I replaced it twice with a cheap Ebay one which was 23$ still didnt fix my issue. I popped 2 codes for P0505 and a code for Bank 1 sensor low input, so then I replaced both upstream and downstream O2 sensors hoping it would fix my issue. Check engine was off for almost a WEEK with atleast 300-400 miles put on the vehicle but didnt fix it. So I bought a more quality IACV off partsgeek for 70$. Still didnt fix my issue. I also adjusted the idle screw on the throttlebody that also didnt fix my issue. At this point I'm clueless and I'm waiting on a buddy to have time to take a look at it. He told me we might have to dig into this one. And yes I cleared the code after I replaced IAC for the 2nd time the right way with a computer, drove 4 miles to a gas station no check engine, went to leave the gas station the check engine light popped on again. 200$+ later... yeah I'm a bit frustrated guys. Can someone people help? Feel free to contact me!!

 

Check the wiring to the IACV, inspect the plug and make sure the prongs are inserted all the way making full contact, they can get pulled back causing the code to pop, also check for frayed cracked wires on the IACV plug. Check for any breaks using a multi meter.

 

I did check the wiring for the IACV plug in, all pins look good. I checked the wires also, they dont look corroded or frayed. I plugged back in. I do not have a multi meter at the moment. I am starting to believe I got a small vac leak somewhere. It bucks sometimes when I drive with my foot lightly on the pedal maintaining speed for like 2 seconds. Car car runs fine overall. Just in park and neutral it idles high and bounces from 1300RPM to 1700-1800RPM but when I put it in drive it goes back to perfect idle. Somebody's telling me I need a new throttlebody because I adjusted the speed idle screw and apparrantly I'll never get the idle back to where it needs to be lol. but I dont think that's the case or scenario.