for the past year my truck has had problems idling properly. It seems like once the truck sits overnight the next morning when i go to turn it on, the truck will start but turn right back off. it will stay on if i keep my foot on the gas but then it will turn off once i let go. i had to drive with 2 feet for a while but i figured out that if have the truck in park and idle it 3 or more rpms for a while (like 15-20 sec) that the truck will idle properly and i dont have any problems till the next morning. Then the problem starts all over again and im getting tired of doing this does anyone know what the problem might be or how to fix it?
My truck is a 99 f150 5.4L V8

 

Sounds like a classic Idle Air Control valve problem. It's positioned on the top back of the engine and is secured by two screws and has one connector. It's simple to clean with some intake spray cleaner from any parts store. If the problem returns after cleaning it, I would recommend replacing it. You can search within the site for "IAC or idle air control valve. There are lots of references to the exact same problem and symptom.

 

i went and bought somethrottle body & air intake cleaner but what does the air idle look like?

 

The easiest way to find all the information you need for the IAC is to do a search for "rough idle" on these forums.

chknbone

 

The IAC is on the passenger side at the rear of the intake on the 99 5.4. They cost about $30 and it can be a PIA to R&R. I have idle problems with both of my 5.4 about every 25 - 30K miles, I have had no problems claning it and re-installing.

The IAC can be cleaned easily. The most difficult thing about getting the IAC out is getting the plug off - I used a 9 inch set of hemostats to reach back to trip the plug release. I use lighter fluid and acid brush to clean out the carbon/sludge. A little compressed air to dry it out and re-install.

 

how do you get those 2 bolts out Tsquared?

I cant get my ratchet to even click once to loosen the bolts before it hits the bodyup there...

I guess use some small box-end wrenches?

 

does anyone know where i can find a diagram of the 5.4 engine online and a good guide that i can get that tells us everything about our f150s?

 

I don't know of a place on the web (I'm sure there is one someplace...), but I just picked up a $15.00 Chiltons Service Manual for my truck. I get one for any vehicle I get. Shows you where it is and what proper order to remove and replace it is....

It's not like a "mechanics" type of manual with exploded views of all the parts, but it's a good one for doing basic 'shade tree' type of work on your rig.

Good luck!

PS, my truck was doing the same thing, but it also set off the CEL telling me what the deal was. I just replaced it and did not bother with the cleaning...... Cost about $90 from the dealer.......

 

I use a long handle open end wrench to brake the bolt loose. It is tight and you must flip the wrench over for a 1/8 turn. I then use a swivel socket on a driver handle to back them out - I also keep a magnetic pick-up handy as well.

 

Im gonna have to work at it tomorrow.

Mine is starting to idle pretty bad...hopefully I can get this sucker cleaned up.

 

I have a set of those ratchet wrenches, they worked great for this.

Rick

 

thank you all!

 

i finally changed my iac a few days ago and it feels like i got a new truck, fixed the problem immediately. i would suggest to anyone that is going to replace their iac to use a swivel socket or if you can afford it have the dealer or someone else do it for you (just to aviod the headache!). thanks for all the imput, another helped member

 

There have been several updates to the design of the IAC, so if you are driving an '01 or earlier, you may consider getting a new one from Ford. And be REAL careful you don't drop the bolts.

I cleaned the one on my F-150 without pulling it. I took off the supply hose and shot some carb cleaner into it. Let it soak and problem went away. I've had two replaced on my LOML's '97 Expy.

 

I had this problem while up at the hunting camp last week. When I returned from camp to Florida, the problem went away. Does air temp affect the IAC's operation? Temps at camp were in the 20-30's and Back home was closer to the mid 70's. Would the IAT sensor have anything to do with this kind of problem??? Any suggestions??? Thanks in advance...