Engine misses when cold
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Engine misses when cold
I have an 84 Ford F250 with a 351 windsor in it. As winter is getting ever closer in the morning when its cold outside my engine misses. As soon as shes hot runs perfect. But when its cold it misses under all situations till its nice and hot. I have all aftermarket stuff on this engine so I dont have the stock air cleaner that has the heating for the headers. What can I do to fix this missing? kinda aggravting when I wanna drive it in the morning. The choke is set correctly and I have a high idle in the morning.
What can I do to help this? Im probably pointing to the fuel not atomzing when its cold. Any help appreciated!
What can I do to help this? Im probably pointing to the fuel not atomzing when its cold. Any help appreciated!
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From: Virginia
You can install the original aircleaner and hook the hot air feature back up. I did this on my 351w, and it ran so much better in the winter, especially in damp weather. I had headers too, so I made a little heat stove out of aluminum flashing I bought at Lowe's. Here's a picture of how I made mine. It doesn't have to be fancy, and you would be surprised how much warm air it generates. You can put your hand on the hose going to the aircleaner, and it starts getting warm in a couple seconds of running. The temp sensor in the aircleaner works pretty good too. It will actually modulate the damper door up and down to maintain a even temperature.
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hmmm thanks franklin! i threw that air cleaner away cause it was all mangled up when I redid the motor. didnt even think about it. Ill go steal it off my friends parts truck and paint it. Yea I know the heat helps a lot those headers Heat FAST! I doubt it but, do u think it would affect performance at all? going from an open element to the stocker?
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It won't flow as much as a open aircleaner element, but for a truck doing daily chores, you won't notice much difference. You can run the stock aircleaner in the winter, and run the open one in the summer.
One thing you might notice if you get down on it is the secondaries may open a little bit sooner. The low pressure caused by more restricted airflow of the stock aircleaner will tend to give more signal to the vacuum diaphragm for the secondaries.
One thing you might notice if you get down on it is the secondaries may open a little bit sooner. The low pressure caused by more restricted airflow of the stock aircleaner will tend to give more signal to the vacuum diaphragm for the secondaries.
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hmmm excellent point about the secondaries. Might get better mialeage to cause of the turbulence of the open element. so my issue is the fuel simply isnt atomizing because it is to cold? Or its not burning? Id like to know for future reference. Thanks for the help Franklin!
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Yes, it's not atomizing, and in some cases especially in damp weather, frost will build up in the throat of the carb. The venturi and the evaporating fuel causes the carb throat to get very cold. I don't know if you have used a spray can or an air tool for a long time and had it get cold in your hand, but it's the same thing.
The engine will not burn liquid fuel. The fuel has to be atomized and suspended in the air flow. What happens is it hits the cold intake manifold, and turns back to a liquid. Then the liquid fuel rolls around in the bottom of the intake, which gets slurped into some cylinders and they run rich, and the other cylinders just get air, so they are running lean. That's why it runs so rough when it's cold.
The air cleaner hot air was only one of the systems the factory used for warm-up. The other was a heat riser valve in the exhaust manifold. It was a valve that blocked the exhaust coming out of the manifold, and this forced it up into a passage that goes from one cylinder head to the other, right underneath the carb. This created a hot spot right on the floor of the intake manifold, so when the fuel hits it, it has a tendency to help keep it atomized. And it also warmed the bottom of the carb area up faster too. Of course when you put headers on, or jerk all the vacauum lines off, you lose this feature.
The engine will not burn liquid fuel. The fuel has to be atomized and suspended in the air flow. What happens is it hits the cold intake manifold, and turns back to a liquid. Then the liquid fuel rolls around in the bottom of the intake, which gets slurped into some cylinders and they run rich, and the other cylinders just get air, so they are running lean. That's why it runs so rough when it's cold.
The air cleaner hot air was only one of the systems the factory used for warm-up. The other was a heat riser valve in the exhaust manifold. It was a valve that blocked the exhaust coming out of the manifold, and this forced it up into a passage that goes from one cylinder head to the other, right underneath the carb. This created a hot spot right on the floor of the intake manifold, so when the fuel hits it, it has a tendency to help keep it atomized. And it also warmed the bottom of the carb area up faster too. Of course when you put headers on, or jerk all the vacauum lines off, you lose this feature.
Last edited by Franklin2; Oct 26, 2007 at 06:46 PM.
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