amej8

I've had this on going battle with P0505 for....damn it's coming up on a year in a couple of months. It originally started when I cleaned the original IACV at around 210-215k miles. Then I got a new IACV maybe 4-6 months ago from the same 99 d16y8 except with way less mileage (supposedly). Nothing changed. Then I remembered my friend gave me his Haynes manual when he sold his Civic so I looked up how to adjust the idle and the problem magically went away. I had the idle adjusted WAY too high from a while back. Then the damn code came back. And so after finally feeling motivated, I went to adjust the idle again today. The idle adjuster screw is currently turned all the way in. The idle still bounces and stays up high unless I really blip the gas. If I lightly tap it or hold it and then let off very slowly, the idle won't come back down.

Symptoms:

#1. When the engine is warmed up, the idles bounce up and down between 1k and 2k. ***No matter if I have a CEL or not, this symptom is ALWAYS occuring.***

#2. When the engine is warmed up and I am NOT in gear, at idle, stopped, after a few minutes, the rev's will go up and start bouncing very fast between 1400 and 1600. If I give it a little gas, the idle keeps bouncing but it does it harder. A little more gas and it'll bounce even harder and rock the engine even more. Then when I give it a lot of gas, it'll finally break free and rev up like normal. Then when the idle drops, it goes back to bouncing between 1400 and 1600. If I drive after this happens, the car bogs and shakes really hard if I'm under 2k RPM's. If I keep the RPM above 2k, it drives normal. Also, if I push the gas pedal while I'm moving in gear, the engine rocks really hard. Same goes if I let off the gas. The only way to fix this bouncing and bogging issue is if I simply turn the car off then back on. The car doesn't even have to be off for long. I literally flick the key off then on (in less than a second) and the problem is gone until I'm stuck again at the next stop. The CEL still stays on and the rev'ing between 1k and 2k still occurs.

Again, the idle screw is turned all the way in. I checked all vacuum lines and they are good. I have no idea what could be causing this. The video is below. You'll notice at 52 seconds, when I lightly give it gas, the rev's go up and don't come back down. When I finally get back in the car towards the end and blip the throttle hard, the idle finally comes back down.

Video link:
http://s592.photobucket.com/albums/t...t=IMG_0009.mp4

Does anyone have any ideas on what I could do to fix this?

twocross

What have you tested/diagnosed so far? I went through this recently and fixed the idle. I may insight for you.

amej8

I don't know how to test anything. But I physically touched and checked all the lines I could see in the engine bay for any cracks/leaks or anything that may not have been hooked up. I doubt anything isn't hooked up because when I originally got the P0505, I didn't touch anything BUT the IACV. Same goes with after that.

amej8

Bump for any help.

apexi_rsx

did you bleed ur coolant system at all? did u take the coolant lines off when u cleaned it? if air is trapped it could cause this. then u should reset the ecu. also look for any vacuum leaks maybe spray carb cleaner around the motor and vacuum lines and see if it revs higher or chokes alil.

twocross

One way or another too much air is being introduced into your engine. Whether it is a malfunctioning IACV (at operating temp.), vacuum leak via vacuum line, or gasket leak at your intake manifold/cylinder head interface; throttle body/intake manifold interface.

Do you have a multimeter to test electrical reference/output voltages?

Willingness to learn more importantly?