2000 Ex D16Y8 IAC malfunction

Ruumiskai

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I've had this civic for about 2 months and am slowly discovering its issues as the cold weather sets in. Now that it's in the 30/20's °f it struggles to stay started on cold start and I have to gently give it gas til it figures its life out. All starts after are normal unless it sits long enough to get completely cold again. Also has intermittent P0505, only shows up after stopping at a light, bucks like crazy unless you really get into the accelerator until I can pullover and clear the code. Once code is cleared its fairly normal. I've noticed the colder its gotten the more frequently the code appears, followed by some hesitation after clearing. Previous owner "deleted" air assist valve with some jb weld, stuck a bolt in the corresponding hose in the intake hose and capped the nipple on the manifold. They also disconnected the breather hose, tried reconnecting and the car refused to start. The rpms do not surge when idling, throttle position sensor when idling is between 8.6-9%. Any recommendations before I start throwing money at this???
 

Brak

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when you say "air assist valve, are you referring to this?
31941
it's not a big deal, most of us don't even have it connected.
Mine is broken off.


Based on the code, and the symptoms, i would check the IACV.
it manages how much air is provided to the engine when the throttle is closed.
It would probably explain issues when cold, or coming to a stop.

they need to be cleaned periodically, or if it's all gummed up, it's an easy replacement.

I'd pull it and the throttle body, and give them both a good cleaning.
Also, i'd double check the hose routing while you're in there.

The manual will be a big help there.
 


Ruumiskai

New Member
Brak said:
when you say "air assist valve, are you referring to this?
View attachment 31941
it's not a big deal, most of us don't even have it connected.
Mine is broken off.


Based on the code, and the symptoms, i would check the IACV.
it manages how much air is provided to the engine when the throttle is closed.
It would probably explain issues when cold, or coming to a stop.

they need to be cleaned periodically, or if it's all gummed up, it's an easy replacement.

I'd pull it and the throttle body, and give them both a good cleaning.
Also, i'd double check the hose routing while you're in there.

The manual will be a big help there.
Click to expand...
Yeah that's what I'm talking about, he filled the area that goes with jb weld, stuck a bolt in the hose for it coming off the intake hose, and capped the nipple behind the injectors. The breather hose was also disconnected, but he left it unplugged. Reconnecting results in the car not starting. The entire thing is a cluster of wtf.
 


Brak

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do you still have the factory airbox?
The nipple on the valve cover goes directly to the airbox, as part of the PCV system.

I'm curious where this metal tube goes.
31945

I guess the first step will be to ensure the vacuum lines are correct, and that there aren't any leaks.
Vacuum leaks are bad

Here's the routing from the Manual.

31944

If you don't already have the manual, ND4Sped has them available for download, on his site...
https://www.tunanocrustgarage.com/service-manuals
 

nd4sped

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That air tube will not affect any starting conditions by any means. Rather it SHOULD have NO relevance on starting or even the car running for that matter. Having it connected just ensures that emission vapors will not escape to the atmosphere and will be processed by the engines combustion.
I would like to see the condition recreated with with a video if possible.

As for the battery voltage, it is below normal by a solid 1 volt. Battery voltage alone should have a stable ~12.7v. Voltage with the car running should be around 14.5v.

More fun facts related to battery voltage and ultimately your alternator and charging system as a whole.
With the car running, above 15v there is a voltage regulator problem in the alternator, below 14v generally is a failing alternator due to undercharging. Sometimes this undercharging issue is resolved by driving in a lower gear to raise RPM and that's a tale-tale sign the alternator is kaput. You can quick test a an alternator by turning on ALL of your accessories to their max settings, including defrost, high beams, etc. Not necessarily the volume.
 
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nd4sped

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OMG and I see an OEM brake master cylinder. Don't see many of those anymore.....I almost want to buy yours and mail you a new one. :lol:
 

Ruumiskai

New Member
So not able to get a vid until building management leaves lmfao. Not supposed to be doing car stuff in my complex. Did just run some errands though so was able to pull some numbers. Engine in on position but not running 11.6v, engine running no lights 14.4v, and running with lights, stereo, defroster 14.6v. Recorded some live data of calculated engine load, rpms, coolant temp, intake air temperature, throttle position, and intake manifold absolute pressure while driving if that would be of use idk. Still haven't been able to capture the info while throwing a code.
 

Brak

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5+ Year Member
nd4sped said:
That air tube will not affect any starting conditions by any means. Rather it SHOULD have NO relevance on starting or even the car running for that matter. Having it connected just ensures that emission vapors will not escape to the atmosphere and will be processed by the engines combustion.
Click to expand...
Exactly why i was curious about it... wondered if it was connected to something it shouldn't be...

from the updated pic, that is definitely a stock airbox, so it shouldn't cause any starting woes...
any chance the hard tube is plugged up with dirt or something (Mud daubers common in the area)?


nd4sped said:
OMG and I see an OEM brake master cylinder. Don't see many of those anymore.....I almost want to buy yours and mail you a new one. :lol:
Click to expand...
Pretty sure mine is OEM...
I'll trade ya! :lol:
 

Brak

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5+ Year Member
One other thing...
DO NOT GET RID OF THE STOCK AIR BOX!!!

people always swap in those stupid "cold air intakes" that do nothing but make the engine loud, and suck hot air from inside the engine compartment.
 
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