Can't figure this P0505 out

[travie_vtec]

I have searched, and it honestly seems like no one has fixed it


Got a CEl the one night, P0505.

I thought I fixed it. Changed the IACV. Found a vacuum leak. Capped everything off. Got rid of a cracked vacuum tank that had no purpose. Relearned the ECU. Burped the coolant.

I got an Innova 3100 obd2 scanner. When I used it, it said I had 2 codes, both P0505. When I clear then, I got a yellow light on the obd2 reader for the emissions saying there's a problem. Once I start driving, the car seems fine. If I park and and turn it off and check the OBD2 reader, i still see a p0505... even with no CEL.

The other day I removed the vacuum tank for cruise control, and capped off the hose that goes to it. I checked my OBD2, no codes, and a green emissions light. I thought I was done... this i got to work and sat in the parking lot in Park, and then my idles gots up and I see that CEL. FML

I still get an idle that slowly goes from 1000 to 1500 and then after a minute of two, drops to 8-900, then gives me a CEL, and a constant ~1500 rpms.

I have searched and searched, asked the jerks on H-T (with very little help or replies).

Am I missing a vacuum hose? i know theres a hose that goes down through the intake mani, but I can't seem to find where it goes.


Car is a 1999 Honda Civic EX with a "D15Y8" and is automatic

Will adjusting the idle screw possibly fix this?

Car does not overheat

 

[00siboy]

No need to ever adjust the idle screw, they are set from the factory to where they need to be.

If the idle relearn was done correctly, I would say that it sounds like you still have a vacuum leak, such as the intake manifold gasket. The fastest way that I check for vacuum leaks is by spraying some aerosol carb cleaner around every gasket, hose, etc. and when the engine starts to run rough, thats where the leak is. Without visually seeing the engine its hard to suggest much more since the fix is usually a new IACV.

 

[travie_vtec]

Pics still wont help :/ it all happened when the guy who changed my oil accidently unplugged the cruise control vac hose from the IM. since then its been hooked up but i still get CEL.

 

[00siboy]

I guess just try the carb cleaner trick and see if you find anything. Props for taking pics tho, most people who want help are too lazy...

 

[travie_vtec]

I used around 7 cans of brake/carb cleaner and still no luck. Maybe a sensors bad :/

I also replaced the PCV valve. Its a Purlator one, not OEM, and im not 100% if it fits perfectly.

 

[98ej8]

You should never have to replace the PCV valve on Hondas, unless the car hasn't been maintained well, but if you do, use OEM only.

 

[00siboy]

Could be air in the cooling system giving the IACV an inaccurate reading. Have you had any coolant leaks or service done to the cooling system recently?

 

[travie_vtec]

None really.. minus the fact that the motor was rebuilt and finished in november

 

[JohnS.]

I had the same code for like a year and I re-adjusted the idle via idle screw and it went away. It turns out I had the idle adjusted too high.

 

[travie_vtec]

my screw is all the way down, and it wont idle under 1k

 

[00siboy]

Have you checked the coolant lines going to the IACV to make sure they are routed correctly? Its not likely but I'm trying to throw out ideas. It still seems like a vacuum leak or idle control problem but you have pretty much ruled those out. Any recent mods?