H4Y3S

So here is a little background. 2000 Honda Civic EX had a cracked block. I bought a replacement Japanese motor and swapped everything from the d16y8 from the old motor to the new motor so the sensors/harness matched.

Got everything back together and started driving it and it throws the P0505 when it gets up to temperature. Pulled the throttle body and cleaned it, threw a new map sensor on it from the newer replacement motor and it went away for a day or so.

Now Monday morning in the rain in traffic the P0505 popped back up. I sprayed intake manifold cleaner around the hoses to look for a vacuum leak and the only thing that it stuttered was around where the intake manifold where it meets the block. I replaced the hose that goes from the intake manifold to the air assist solenoid valve and it still stutters around the intake where it meets the block. Do you think it would be best to replace the intake manifold gasket again or just loosen and retorque? This has to be the most obnoxious CEL when driving a manual.

apexi_rsx

clean the IACV it is located on the back of the intake manifold and is held on by 2 12mm bolts and 2 coolant lines.... clean it with carb cleaner and blow it out with some air. if it continues to come back replace it.....

jbpnoman

P0505 is IAC malfunction. Remove your IAC, clean it out, and reinstall it.

H4Y3S

I will give that a try this evening when I get home.

Psychoteen101

Definitely fix that vacuum leak at the manifold as well. Try a new gasket. if that doesnt work, you could try some spray on sealant on the gasket surface.

Former User

You have an intake air leak. Fix it and P0505 will go away.

And by the way, a bad MAP sensor would not throw P0505.

H4Y3S

Well so far so good, drive in this morning was CEL free. The IACV was caked pretty bad with dirt. Cleaned it out and no CEL (knock on wood). I think I am going to put off pulling the manifold until I get another CEL, don't want to spend any more time on this car. I figured might as well through a newer map sensor on, the motor that I swapped out was 253k and judging by the look of the new motor and how clean it was I would guess it had less than 50k.

H4Y3S

Side note, what is the correct plug gap? Couldn't find it in the book so I set it to .4

sleepyaccord96

thats ok

apexi_rsx

most ngk plugs are gapped .35 from the factory.... and shouldnt need gapped... you should be fine with .4 though

H4Y3S

So at least I got one day of no codes. The CEL came back as I was pulling into the parking garage this morning and judging by the idle it looks like it is the same problem. Could the seal being off where the intake meets the block also put the same code as the iacv? I replaced the gasket and cleaned the manifold and block when we switched the jap intake with the one from the bad block.

HondaCivicD

i just got done fighting this problem on my 98 ex. after cleaning the IAC valve it went away for about a month, then it came back. i then replaced my intake mani gasket and now a month later it hasnt come back on, hopefully it won't. but i figured if it does im gonna brake down and spend the money on the new IAC valve. i would replace the gasket first and if it comes back then check the valve

H4Y3S

Well I checked the code again and it looks like it is putting out 2 P0505 codes. Cleared it out, pulled the IACV again and it looks super clean on the inside, both coming from the throttle body (cleaned that last weekend and its sparkling now)and the intake side. I bought the manifold gasket from Bap-Geon and they usually have good parts. Should I go to something like a Napa or something else and grab a felpro or something generic in addition to using some liquid gasket? It does still have the bouncing idle but no CEL yet today. Side note, the washer on the IACV looks pretty compacted.

Psychoteen101

Take care of the problem you know exists. Youre relying too much on what the code is telling you. You know for sure the intake gasket is leaking, so get that issue resolved since its in the same realm the CEL is getting caused by. Yes, that code can be cause by the manifold leaking. MAke sure you thoroughly sand and clean the surface of the manifold and cylinder head. Unless something is warped, you shouldnt need liquid gasket. But it wont hurt to use it if you think it will help.

H4Y3S

Thanks for the info guys. If I get around to fixing it I will update. I am a little burnt out from swapping the engine and then working all the little kinks out. The car is driveable and the cel doesn't come back as long as you don't let the computer handle the idle.