Leaving this for too long can cause misfires, rough running, vacuum leaks and you will have a more extensive repair on your hands. The PCV valve hose may have a leak in it, which is causing the hissing sound. If you hear a hissing sound from the engine, it is time to get your vehicle looked at. A misfire will sound like the engine has a vibration to it is a sign it is not running properly. This can be from a loss of vacuum due to the hose not working properly because of a leak, the hose being pinched, or becoming clogged from buildup over time. Misfiring while idlingĪnother symptom of a bad or failing PCV valve hose is your vehicle will misfire while it is idling. The mechanics at YourMechanic can diagnose the exact reason the Check Engine Light is on, whether it is the PCV valve hose, the PCV valve, or a combination of parts. This is because the PCV valve hose works directly with your engine to ensure everything is working properly. The Check Engine Light may come on for a variety of reasons, and one of them is a failing PCV valve hose. If you suspect a PCV valve hose is the reason you have been getting poor fuel economy, contact the professionals at YourMechanic to have your PCV valve hose replaced. This is because the vacuum on the intake side of the cylinder head will not be able to properly signal the correct amount of fuel that needs to be fed into the engine and can result in a lean or rich engine condition. If the PCV valve hose is clogged or has a leak, it may cause poor fuel economy. There are a few symptoms to watch out for when you have a bad or failing PCV valve hose. If the PCV valve hose breaks, the gas will not be transferred back into the engine, and your vehicle will be less efficient and have increased emissions. From there, it is added to the intake manifold and used by the engine. The two "towers", for lack of a better term, located in front of the choke plate, should be bowl vents.The Positive Crankcase Ventilation (PCV) valve hose transfers excess gasses from the crankcase to the PCV valve. You would have to remove the airhorn to check for sure but, there should be three open vent holes into the bowl. If everything works, it runs good and you're satisfied with it, you shouldn't have to change anything.Īs for the carb bowl vent, the plugged hose was likely the vapor return line to the vapor canister on whatever vehicle the carb came from. If it were my engine, I would probably connect it that way but, that's just me. The PCV, transmission and power brakes, if your truck had them, would all get constant vacuum from the manifold. The PCV valve goes into a thick hose, then into a reducer for a smaller hose, then plugs into the carb on the front drivers side, under the accelerator pump. Right now the threaded hole on the back of the manifold is connected to the transmission, so if I connect the PCV to it, where would I connect the transmission hose? Or would I add a splitter? The hole is in an intake runner so would be a vacuum source. On this manifold, you could use the large threaded hole at the back for the PCV hose fitting. The port on the back of the manifold connects to the transmission on mine, I assume that's correct. Mac3687 wrote:If it helps in the meantime, here's the spacer I have: I have no idea if the current setup is okay or if I should change anything. Gasket #1933 adapter in place, which does not have that big PCV port on it, hence the routing you can see in my drawing. Because the previous owner put a 2 barrel carb on a 4 barrel intake, there's a Mr. The big thing that I'm confused about is every photo/diagram I see shows a carb spacer that has a vacuum port on the back, that links directly to the PCV valve. I can take photos, but I figured this would get the gist of the routing across: I am however a tinkerer and I've always worried I didn't have everything connected right, and am ready to fix it. I've had the truck for three years, it's been my daily driver for most of that time, and it generally seems to run fine. My dilemma is that I have no idea if my vacuum lines are routed properly. No dashpot, but there is a choke unloader (or are those the same thing?) Forgive my ignorance here, I'm more of a motorcycle guy, and when it comes to some items on my truck, I'm a little lost.įor reference, here's what I'm working with:ġ969 F100 (I was told the engine was from a 1970 truck)
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