Rough idle

So my truck is unhappy lately. 2001 5.4 runs rough when it's below freezing. I have replaced the iac and cleaned the maf. Plugs have been done. I'm at a loss and about to drive this thing off a cliff. Any ideas. I know someone has had this problem before. Help a brother out

 

I should have said my idle surges until the truck gets warm. After it's at running temp it's fine

 

Sounds like a vacuum leak could seal up when warm.

 

Thanks. Anyone else have ideas?

 

Intake manifold gaskets? Does the 5.4 have intake manifold 'gaskets'? I just did them on my sisters 4.0 exploder. Had the same symptoms.


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He has the composite manifold as far as I know.

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Yeah, on the exploder it creates a vacuum leak that deals up when the o rings expand , just like you suggested.

I think you're more correcter ha ha. Vacuum leak. I think if the intake manifold leaks, it leaks coolant which creates a misfire that won't go away. That's what happened on Denny's 5.4.


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Thanks fellas. Tired of messing with it. Going to the shop on wednesday to have it looked at. Weird thing is it only does it when it's below freezing otherwise it runs like a top

 

You have a summer truck.

Maybe get a Ranger with steel heads for winter ???

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I wish but three kids don't fit in a ranger very well lol