Hello,

I have a 99 f150 5.4. Starting about a month back i got a check engine light. I went to the local auto parts store and had the codes pulled. I can't rember but i think it was P0174 System Too Lean - Bank No. 2. I rember it being bank 2 lean. I have dissconnected the battery and it came back. Well today my wife drove it to work. When leaving it started up and idled real rough like it wasnt hitting on all 8. Putting it in gear it would die. I came to where she was at and was able to drive it home but it was idleing real low and rpms would drop real quick when letting off the gas. Once i got going it drove ok, didnt stumble just when letting off the gas to come to a stop or slow down. I replaced a vacume hose that had a split in it about a 1/2 inch long and was pinched. I started it up and it still idled real low. The passenger side of the engine seemed real quiet like it wasnt firing. I gave it some gas and it picked up and now it seems to be running like normal. The rpms were normal at idle. Also i have noticed that the throttle pedal is stiff when first starting up but then it is smooth again after giving it some gas. It has been real cold here in Texas the last few days and it has sat in the driveway for about 4 days and today was the first day it has been driven.

Thank you

 

Great post.
Now we all know that clearing the codes does not repair the problem.
A free lesson for everyone.

I suggest changing out the IAC valve for your issue.
Also, if it hasn't had new Motorcraft double platinum spark plugs installed properly in the previous 50,000 miles or so, I would do that.
The PCV hose tends too dry out and crack & leak, so check that and maybe replace the PCV valve while you have it out or clean it with some aerosol carb cleaner.
You can clean the MAF with some electrical cleaner.
There is some other stuff you could do, as these vehicles do need some maintenance from time-to-time to keep them running properly.

You can read through these threads and see the problems that others have with these vehicles and see what they did to fix them. Or not.

 

Thanks for the reply. I changed the plugs about 20k ago. The truck has around 130k on it now. It is running good today when i drove my son to school. I plan on checking IAC and the vacume hose that runs behind it. I am also planning on cleaning the MAF and the throttle body and linkage. I replaced a vacume hose yesterday, it had a 1/2 inch crack/slit in it and was pinched in where it bends.

Thank you

 

Does the truck surge up and down on idle?

 

I worked on it a bit more yesterday. I replaced another vacume hose/fitting. It was one of the ones coming off the pvc valve in the valve cover that is a 90 degree bend. It had a crack but didn't look like it went all the way trough, but replaced it anyway. I also looked at the throttle body and it is just caked with crud. I wipped it down a bit but didnt really clean it. The trucks throttle response is alot better and the pedal isnt sticking when i first start it up. It would always be a little stiff whenever i start it and go to apply some gas to start moving but then it would be fine, only did it at the first start ups. The idle does fluctate a bit right in the morning when i first start it. It just recently started to do this. It seems to be better now. I also noticed that there is a swooshing sound when i was in the engine compartent and i would crack the throttle. It was like a quick sucking sound. Now i also have a 02 expedition with a 5.4 and it does not make this sound. It sounds like i have a aftermarket intake on it. That sound they make when it sucks air in. It sounds almost like it is coming from behind the throttle body. I know there is another vacume hose behind the IAC but it is hard to get to. I was going to take a look at it when i get some cleaner and pull the throttle body off to give it a ggod cleaning.