DJP

Just a quick question. Would changing the PCV valve on my 92 civic si hatch significanlty improve idle, and gas milage?

suspendedHatch

Yes it could if it needs replacing. Take it out and shake it. If you can't hear the metal ball inside bouncing back and forth, try squirting it out with some carb cleaner. If it still doesn't move freely, spend the $3 for a new one.

thesmogman

I don't recommend cleaning, it can make it worse....So change the thing out.

And yes if it is bad it can.

DJP

That is the second time I've heard that about the PCV valve, but I don't think the one for my car has that. From my research I saw that the inside of it includes a spring, and a small pieice of plastic that moves and allows air flow depending on the crankcase pressure. I bought a brand new one today, and shook it while I was in the store, and I still didn't hear any ball shaking.

hrs-parker

iTrader: (3)

if its a honda you got one...

95vxtealhatch

yes, from what ive heard pcv will make a diff in gas milage and idle quality.

slowcivic2k

It can help idle quality, but this all depends on the condition of the valve. Every valve I have used was made by Nippondenso, and has a spring loaded pintle, so you wont hear it when you shake it. The only way to tell is to suck from the manifold side and if air passes through it. Then blow on it and make sure air does not pass through it.

I highly recommend setting base idle after replacing it. Unplug the IACV with the engine fully hot, idle at this moment should be 450rpm. If it stalls, adjust the idle bleed screw on the throttle body until 450rpm is maintained. After that is finished, plug the IACV back in, and your idle will jump to 700-750rpm, which is specification.

More important than idle is oil consumption. A poor PCV system can cause black paste-like soot in the intake tube and throttle valve. This can also contribute to poor idle quality. If this is the case, **** the throttle plate open, and at least clean the sealing edges of the valve.

Brick Top

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by slowcivic2k &raquo;</TD></TR><TR><TD CLASS="quote"> A poor PCV system can cause black paste-like soot in the intake tube and throttle valve. </TD></TR></TABLE>

I usually see that happen when the pcv valve is stuck closed. the crank case can't breath and goes back up through the oil return holes to the vc. the honda pcv system is a poor setup anyways.

DJP

Wow, thanks for all the information people. As for adjusting the idle, i had no idea that was neccessary. I thought that replacing the PCV valve would be a simple fix. What happens if i don't adjust the idle?

slowcivic2k

Because every valve is different, the amount of air it lets through is different, therefor it is good practice to reset the idle after changing any components that adjusts/modifies the idle.

It is not mandatory, but highly recommended.

DJP

Considering that I haven't dealt with the IACV or it's control screw, where in the engine bay are these things located?

slowcivic2k

Throttle set screw is on the front of the throttle body on the top in the center. It's a brass looking screw. The IACV is on the back of the intake manifold next to the brake booster vacuum line. There is a connector that plugs into it, unplug that when your ready to start.

DJP

Alright, sounds good. Thanks for the help.