Ok everyone, my truck is acting nuts! I live in michigan and now after 3 days of straight rain, and not driving my truck. I climb in today, start er up and shes idling a little rough, ok maybe shes just a little damp. I start driving to work, and she is shaking like Michael Jackson. Now here is the weird part, it only shakes at idle/lower RPMS. This means that when I am under gas she runs smooth and doesn't shake. But when I hit about 60 and she upshifts into overdrive it shakes again. And I really don't think its the trans because I put it in neutral/park etc and it didn't help. Now on the way home I started it up, check engine light is on, and its doing it again. I make it home safe, and get out and you can just hear it gulping air/mis-firing. I am really really lost on this. Truck is a 99 f-150 5.4 with 39,000 miles. I am really hoping this is not major. Luckily I have another 2 vehicles to drive for the next week, because my family is going out of town (I have to drive a dodge ram 1500... not fun) anyway I was just hoping you guys might have a piece of information on what its doing. I am gonna spray some WD on her incase its just a dampness mis-fire and then take it up to get a tune-up. But I just love this truck, and it finally started to get about 16 mpg and I love it. Thank you all so much for your wealth of information and understanding. God Bless.

Jon

 

I need to know the codes to help you out, Lots of things can cause this, but check everywhere for vacuum leaks, esp. in the PCV system.

 

Ya im sorry about that, no codes yet, no one open/no time over the next couple of days. I will tell you what though, this truck is still a brute with all these issues to be able to cruise at 60 im very impressed.

 

Go to a advance or a autozone, they will give you the codes for free.

 

Sitting out in the rain like that, I'd possibly suspect damp cops. You do need to read out the codes to see if they are misfire codes or something else though.