PCV valve question

98CobraStarLSC

98CobraStarLSC

Dedicated LVC Member
Joined
Mar 22, 2008
Messages
664
Reaction score
0
Location
Spring
I am running the cobra intake manifold and i was looking at the hose coming out of the valve cover and saw that it was just hanging there. Anyone got pictures of their setup?

Maybe this would explain my high idle/ horrible fuel milage problemo!
 
Ok on one side should be a hose, for me passenger side, that then connects to the intake tube before the throttle body.

The other side, with the PCV valve, goes from valve to intake.

From your description it sounds like you dont have the one hooked up to the intake tube?
 
i have a tube coming off the pass side valve cover to a "T" and both ends are just hanging there. ? where is the pcv valve at? on a cobra intake manifold
 
ok scratch that last one! haha thanks unity. I now see the drivers side going to the intake manifold.. Thats the pcv valve. What about the pass side valve cover? is that just a breather? i noticed if i plug it with my fingers, there is suction.. should i cap it off or does it really need to be in the intake tube before the throttle body?
 
I though the PCV was on the drivers side.

Remember, the PCV has two hoses. One that pulls from the intake tube then into the valve cover where its routed to the timing cover then into the other valve cover where the PCV valve sits - its then sucked via the intake vacuum into the intake. The PCV valve is sorta like a throttle for the volume of air that cycles through.
 
98CobraStarLSC said:
ok scratch that last one! haha thanks unity. I now see the drivers side going to the intake manifold.. Thats the pcv valve. What about the pass side valve cover? is that just a breather? i noticed if i plug it with my fingers, there is suction.. should i cap it off or does it really need to be in the intake tube before the throttle body?
Click to expand...

We posted at the same time, read what I described above. Two sides to the system, that hole with the vacuum you are covering eventually feeds back to the PCV.

You basically have a big vacuum leak right now! Would explain A LOT! Get er fixed and drive it like you stole it! LOL
 
you know how the factory gen II manifold, the pcv line Y's into the 2 that go into the intake manifold? well i combined them into 1 since the cobra one doesnt seem to have 2 connections.. is that what you mean?

you can see in my advitar, right above the IAC the 1 hose going in instead of the 2 on a stock manifold

is it a problem that it is not in the intake tube then?
 
Um. Not sure how a Gen II is setup. I have a Mach intake on an 04 engine in my 96! LOL

But I am using a Gen II intake tube. There should be two opening right before the throttle body. One is for the IAT sensor and the other should be for a hose that connect to the passenger valve cover.

On the other side, it should be a straight forward as seen below. From the PCV valve to the intake.

web.jpg
 
Ok, here is how it works. This may help. You can see the upper most arrow on the left points to a hose. It bends down below the fuel lines, in my case, and then to the valve cover. No valve on this end. You need to have this hooked up so the air entering the engine is metered.

web.jpg
 
so would that not being connected to metered air cause a high idle/ IAC code? possibly??
 
You better believe it. You basically have a controlled vacuum leak, and its being controlled by the PCV valve. If that valve was bad or missing I bet it would be a big enough leak to kill the engine outright.
 
Alright i hooked it up and still when you start it up it goes to about 2000rpm and hangs for about 1 minute then goes down slowly to about 1100rpm..

wtf? brand new iac !
 
Ya, MAJOR vac leak from this not being setup right. You might be over-cooling the cats too.
 
What about the check engine light. On or off. I just went out and looked at my setup and I had the passenger side valve cover vent loose. But I did cap the intake tube. My car seamed to run alright. Its been that way for over a year. I just reconnected it to the intake tube. No noticable difference. I will leave it connected. Does the hvac work in your car. What about the line to the bottom back of your TB is it connected. Good luck. I hate when my car isn't running right too!
 
Let me try to simplify this.

PCV (Positive Crank Case Ventilation)

What it does is vacuum out the potential harmful fumes our of the crank case. Fume that could result in explosion. It does so by pulling air from one valve cover through the timing cover and out the over valve cover. It keeps a constant flow of fresh air in the upper engine. Its also probably helps to cool things to a small extent.

There are two system setup for this. One uses a down draft tube from one valve cover with a breather on the other valve cover. Found on much older vehicles.

The other uses the vacuum created by the intake to pull the air through.

We use the vacuum system. What happens when you suck on a straw with the other end closed by your finger? You get no air movement. In htrdlincoln98's case, thats what is happening actually. In other words the PVC system is shutdown and fumes are building up.

But lets think about this. For the system to "suck" form the PCV valve you have to get air from somewhere, right? Hence the connection from the intake tube to the other valve cover.

Now since our engine have metered intakes - hence the MAF sensor - the PCM knows exactly how much air is entering the intake and control fuel, air, etc. If you are pulling in air from the PCV valve but the other valve cover is wide open to the outside guess what - you have a second source for air to make it into the engine which is not measured/metered. This is a vacuum leak.

You may or may not get a CE light. If the IAC is full closed when the PCM thinks it should not be then you should, but it may not be full closed since the PCV valve is not quite allowing a full blown leak by springing back and fourth.
 
I see what your saying. I didn't have the other valve cover vent capped it was open to get fresh air. This however never caused any issues with a high idle or a check engine???
 
Odd. It normally would unless your PCV valve is shot. Not that I think about it the spring keep it open I think? So if its worn and the vacuum strong enough it may have just sucked the PCV valve closed?

Just guessing there. But by design you would have had a vac leak.
 
I agree with unity, should be hooked up but the pcv is a one way valve so i dont think you will get a vacuum leak. I think it just always stays closed.

Anyways though i will check the throttle body vacuum line. im trying to see any others.

Is there a way to check with a meter or something how much vacuum i should have to what i have? i would smoke test it but i dont smoke or have a tester. haha

On a side note, its really easy to check your pcv valve. take it off and give it a shake, it should click back and forth. if it doesn't, its stuck and needs to be replaced.
 
A vacuum gauge can be had for under $15. I picked one up and rarely use it, but its a tool to have.

Remember, the "other side" of the PCV system needs to be attached to the intake tube BEFORE the throttle body. If you hook it up to the TB you will just end up on another vacuum source.

As for the PCV, if you shake it, it should not rattle much. Its a sign of a worn spring if it does. At least thats what I have always been told.
 
haha! no if it sticks and doesnt rattle then it is bad. i double checked on all data here at work. they work on vacuum
 
I know they work on vacuum, its a check valve with a spring. Odd, my new ones dont really rattle and my old ones always did real bad. Dunno!
 
alright heres the deal. All looks good on the vacuum lines. I checked my short term and long term fuel trims and they look to be fine! nothing to indicate a very obvious leak. The only thing i can think of but it doesnt make much sense is when i push hard to close the throttle body, it idles down and sometimes dies. I adjusted the idle screw(in the middle of the 2 throttle plates on the bottom of the throttle body) it is facing up since i have the cobra manifold on and got it to idle down a little . but when you first start it, it goes to 2-2200 rpm and then after about 15-20 seconds goes down(i guess when the iac compensates?)

I was thinking maybe when we ported my throttle body, some how air is getting by now. It was doing great for about 6 months after the swap and now it is acting up..
 
You must log in or register to reply here.

Members online

Total: 133 (members: 1, guests: 132)
Back
Top