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Old 07-16-2015, 11:19 PM   #1 (permalink)
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Civic VX - purge cut solenoid?

While looking at a diagram for the stock throttle body, I noticed there was a part on the intake manifold that I don't seem to have on my VX. And that is the "VALVE ASSY., PURGE CUT SOLENOID" which is #11 in the diagram below. The previous owner deleted all the vacuum lines from the charcoal canister, the thicker one that goes to the upper port of the throttle body and the smaller vacuum hose which would go to the valve mentioned above, as well at this valve itself (if it comes with it?).



I am wondering what the purpose of this part is and if it comes on the VX models or only on the other trims. If it normally comes on this engine I'm not sure why someone would remove it, but alas I've figured out the previous owner did a lot of things I'm not fond of.

It seems just deleting the charcoal canister may be the easier route to go, I can't imagine it would affect my gas mileage?


Last edited by GotToyota; 07-17-2015 at 11:47 AM..
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Old 07-17-2015, 03:09 PM   #2 (permalink)
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So after some reading, and quite obviously, this solenoid valve is a part of the evap/emissions system with the charcoal canister. Some have stated that without this valve the car could potentially run rich or develop a smell of fuel. Removing it will also negatively affect gas mileage.

Like I mentioned before, the previous owner removed the one on this car for whatever reason, as well as the other charcoal canister lines.

Before, nothing there but the screw, vacuum line hanging below, plug freely hanging (looks identical to IACV connector but different colored wires).


The valve, which for test purposes, I picked up at Pick-N-Pull for $5. I figured it would be worth the few dollars compared to the $130 price Honda wants for a new one. Also not even sure if it matters, but the top "dome" looking piece is a filter that clips into the valve, it's replaceable and costs $9 from Honda.


Installed with connector back in and correct vacuum hoses, the top nipple connects to the top port of the charcoal canister, the bottom nipple connects right below to the intake manifold.


Followed the diagram here for the vacuum lines:




I am a little disappointed that this did not get rid of my occasional idle issue where it will drop drastically low or sometimes stall. My idle is not sporadic, so I figure it is something small but I have determined there are no vacuum leaks. Will be replacing the map sensor here soon to see if that helps.

I will say though, that the car feels a little smoother at idle. Will it improve my fuel economy? We'll see come the next few tanks.
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Old 07-17-2015, 03:46 PM   #3 (permalink)
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Do you have a scan tool that can read OBD1 data? Because I had a not entirely dissimilar problem a while back. I replacdd the fuel pressure regulator because it fit the symptoms, butin the end it was pinching of the wires from the MAP sensor. What tipped me off in the end was OBD2 data about manifold vacuum. The D15z1 has a MAP sensor, I am sure. And I think I see it there below the solenoid you just installed. You can test its voltage signal if you have no scanner.
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Old 07-17-2015, 03:50 PM   #4 (permalink)
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Unfortunately I don't have an OBD1 scan tool. However you are right, there is a MAP sensor but it's actually located on the top of the throttle body. The sensor you mentioned that's below the purge valve is the air intake temperature (AIT) sensor.
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Old 07-17-2015, 04:23 PM   #5 (permalink)
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Well, I think that MAP is a candidate for voltage signal test. If there is an intermittent open in a wire, or the unit itself is failing after 22 years, well... it is a suspect.
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Old 07-17-2015, 04:28 PM   #6 (permalink)
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Already have a new sensor on order so if that doesn't fix it I'll go from there.
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Old 07-17-2015, 04:50 PM   #7 (permalink)
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Quote:
Originally Posted by GotToyota View Post
Already have a new sensor on order so if that doesn't fix it I'll go from there.
There is a smart guy on Honda-tech.com whose signature says "test don't guess." I think that is important advice, which I follow religiously now. I have two fully working MAP sensors for my car from a moment three or four years ago when I "guessed" and just bought one before I had tried to test. I'd hate to see you waste your money too. If you have the FSM and the tools, save $30 and test that sucker first. Good luck!
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Old 07-17-2015, 05:55 PM   #8 (permalink)
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It's too late now but I completely see where you're going. I'll try to see if I can borrow some test equipment.

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