Just a question. Pcv/ccv
10-23-2018, 08:24 PM
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Year: 1994
Model: Cherokee (XJ)
Engine: 4.0 I6 H.O.
Just a question. Pcv/ccv
On the valve cover we have the pcv and the ccv valve. So let's say someone were to put a pcv on where the ccv is or ccv in the pcvs spot. Only messing up one. Or messing up both. What kind of problems would develop? Would it idle right. Would it have vaccum issues? I am not in a situation like this. Just came across my mind. I searched on here no good answers. So I thought I'd ask the community for any one that has personal experience or knows what will happen. Thank you all!
10-23-2018, 08:45 PM
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Year: 1994
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10-23-2018, 08:50 PM
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The 4.0 does NOT have a PCV valve. A PCV valve is a spring loaded metering valve that is controlled by the vacuum applied to it. This engine has a CCV, which is a constant fixed orifice allowing a certain amount of air to bleed into the intake manifold at any vacuum draw. The Idle Air Control adjusts to compensate for this "air leak" therefore maintaining a constant idle speed. The front fitting is just an elbow that allows air to enter the engine to replace that which is removed by the CCV and is attached to the air filter housing so the air is clean. If there is any blowby gasses from the engine's operation, they are bled thru the CCV and very little air is replenished by the front vent.
IF you switch the 2 fittings, the elbow will allow too much air to enter the intake manifold and the engine may not run or if it does, it will idle very high. The CCV, being in the front in this case, will meter air entering the engine but will cause a vacuum to exist inside the crankcase, probably pulling compression past the rings.
IF you switch the 2 fittings, the elbow will allow too much air to enter the intake manifold and the engine may not run or if it does, it will idle very high. The CCV, being in the front in this case, will meter air entering the engine but will cause a vacuum to exist inside the crankcase, probably pulling compression past the rings.
Last edited by dave1123; 10-23-2018 at 08:56 PM.
10-23-2018, 08:53 PM
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Thank you!!! I am not so sure what sparked that question but excellent answer!
[QUOTE=dave1123;3521743]The 4.0 does NOT have a PCV valve. A PCV valve is a spring loaded metering valve that is controlled by the vacuum applied to it. This engine has a CCV, which is a constant fixed orifice allowing a certain amount of air to bleed into the intake manifold at any vacuum draw. The Idle Air Control adjusts to compensate for this "air leak" therefore maintaining a constant idle speed. The front fitting is just an elbow that allows air to enter the engine to replace that which is removed by the CCV and is attached to the air filter housing so the air is clean. If there is any blowby gasses from the engine's operation, they are bled thru the CCV and very little air is replenished by the front vent.
IF you switch the 2 fittings, the elbow will allow too much air to enter the intake manifold and the engine may not run or if it does, it will idle very high. The CCV, being in the front in this case, will meter air entering the engine but will cause a vacuum to exist inside the crankcase, probably pulling oil past the rings.[/QUOTE]
[QUOTE=dave1123;3521743]The 4.0 does NOT have a PCV valve. A PCV valve is a spring loaded metering valve that is controlled by the vacuum applied to it. This engine has a CCV, which is a constant fixed orifice allowing a certain amount of air to bleed into the intake manifold at any vacuum draw. The Idle Air Control adjusts to compensate for this "air leak" therefore maintaining a constant idle speed. The front fitting is just an elbow that allows air to enter the engine to replace that which is removed by the CCV and is attached to the air filter housing so the air is clean. If there is any blowby gasses from the engine's operation, they are bled thru the CCV and very little air is replenished by the front vent.
IF you switch the 2 fittings, the elbow will allow too much air to enter the intake manifold and the engine may not run or if it does, it will idle very high. The CCV, being in the front in this case, will meter air entering the engine but will cause a vacuum to exist inside the crankcase, probably pulling oil past the rings.[/QUOTE]
10-23-2018, 09:40 PM
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Thank you!!! I am not so sure what sparked that question but excellent answer!
[QUOTE=dave1123;3521743]The 4.0 does NOT have a PCV valve. A PCV valve is a spring loaded metering valve that is controlled by the vacuum applied to it. This engine has a CCV, which is a constant fixed orifice allowing a certain amount of air to bleed into the intake manifold at any vacuum draw. The Idle Air Control adjusts to compensate for this "air leak" therefore maintaining a constant idle speed. The front fitting is just an elbow that allows air to enter the engine to replace that which is removed by the CCV and is attached to the air filter housing so the air is clean. If there is any blowby gasses from the engine's operation, they are bled thru the CCV and very little air is replenished by the front vent.
IF you switch the 2 fittings, the elbow will allow too much air to enter the intake manifold and the engine may not run or if it does, it will idle very high. The CCV, being in the front in this case, will meter air entering the engine but will cause a vacuum to exist inside the crankcase, probably pulling oil past the rings.
[QUOTE=dave1123;3521743]The 4.0 does NOT have a PCV valve. A PCV valve is a spring loaded metering valve that is controlled by the vacuum applied to it. This engine has a CCV, which is a constant fixed orifice allowing a certain amount of air to bleed into the intake manifold at any vacuum draw. The Idle Air Control adjusts to compensate for this "air leak" therefore maintaining a constant idle speed. The front fitting is just an elbow that allows air to enter the engine to replace that which is removed by the CCV and is attached to the air filter housing so the air is clean. If there is any blowby gasses from the engine's operation, they are bled thru the CCV and very little air is replenished by the front vent.
IF you switch the 2 fittings, the elbow will allow too much air to enter the intake manifold and the engine may not run or if it does, it will idle very high. The CCV, being in the front in this case, will meter air entering the engine but will cause a vacuum to exist inside the crankcase, probably pulling oil past the rings.
If you look at each elbow if they proper one in the front has a large pass through hole, where the rear is restricted.
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