1998 F-150 4.6/auto 73,000 miles:

Took a long road trip yesterday from Mid-Missouri down to Tupelo Mississippi. Normally, an 8 hour drive. Yesterday, bad weather made the trip approx. 13 hours. When i got about 50 miles north of Memphis, it was slush being thrown all over by cars and 18 wheelers, then it took 3 hours to go about 4 miles thru Memphis because all of the roads were solid ice. Due to the cold temps, there was lots of idling time, sometimes 20-30 minutes just sitting. Filled up at 3 different gas stations along the way just to keep a full tank thru all the mess.
So I went out tonight to run into the car-wash to rinse all the salt and dirt off my truck, and it wouldnt idle. Died everytime i took my foot off the gas. So i sat with it high idling and let it warm to full operating temp. and it still wouldn't idle. No check engine light, doesnt sound like a mis-fire (truck is running smooth), no weird noises, no blue/black smoke, etc, just plain wont idle.
Truck had spark plugs and a fuel filter about a year ago (15,000 miles ago)

Possible some moisture is blocking spark or some other electrical part? Some sensor bad?

Any suggestions?.....

 

IAC stuck closed, most likely.

Steve

 

how do i go about diagnosing and fixing this? IAC is the idler pulley right?

 

Hello,
I cannot tell you how to diagnose it... IAC is a cylinder thing 3 inch long 1 inch in diameter attached with two bolts (10mm) to the intake manifold right under the plastic cover. If you search the site you could find the pictures and exact location on your truck, it's so common. IAC is around $60 at everywhere so if you find an opened shop it's 10 mins deal to replace. If not try to clean it up with trottle cleaner...
Hope that helps.
Alex.

 

Yep,IAC.Get some throttle body cleaner and let it soak in the IAC for a bit.Use a screwdriver to work the plunger back and forth.This will break any carbon loose on the spring or plunger.This should fix your problem but if it doesnt you can get a new one from any good auto parts store.
BTW,while you're at it clean the throttle body too.
:santa:

 

so i can reach the IAC without taking the throttle body apart from the intake?
Sounds pretty simple, but of course things are always going to be harder than they seem.

 

Did a search on the IAC, read for a long time, and i think that this may be a factor in my problem. Found a couple pics also, but im wondering if someone can point out what / where I need to clean:
I think these pics might be from a 5.4 but i would imagine they'd be pretty close. Ive never torn into my throttle body before, so im kinda new in this area--thanks!






4.6

 

The third pic shows the IAC the best.Its the part bolted down with the two 8mm head bolts.Be careful when removing as not to tear the gasket.If you do Ford is the only place to get it.

 

That's not a 5.4...it's harder to get to the IAC on a 5.4...but yes, it is that little canister. If you are lucky, cleaning it will be good enough. But as has been said, you may have to buy a new one.

 

thanks for the replies--

--What part needs to be cleaned?

--In the 3rd pic, is it inside the large cylindrical shaped on the right or the smaller one on the left?

--Does it have to be removed to be cleaned?

--Are the two 8mm bolts the ones, in the 3rd pic, on either side of the faded white tag that has "AB" on it?



Sorry for all the questions, i just want to know what im doing when i tear into it. Im used to working on older vehicles that are easier to piddle around on, and this is my first time dealing with the throttle body on my newer truck.

 

In the third pic,it is the small cylinder shaped object,with the two bolts holding it on.The bolt heads are 8 mm.And yes,it does have to be removed to clean it.Upon removal you will see two holes in the IAC.This is where you spray the cleaner and let it soak.After that,spray a little more in there and work the plunger.This will release any carbon build up on the plunger and spring.Before you start this project disconnect the negative battery cable.
In the same pic,the bigger part to the right is the throttle body.When you remove the rubber elbow from it,you will want to clean inside there with the throttle body cleaner.Use a soft bristle toothbrush to scrub the walls and the butterfly plate,front and back.Open the butterfly by operating the cable on the throttle body.Spray everything down when done.
If you feel this is a little much for you to do,have a friend help or a mechanic you trust.


:santa:

 

thanks for the help, im not scared of doing this ive done much more but ive never really worked on my 98 before. Ill start on it and let you know how it goes

 

In the second pic the IAC is the part with the "dot "on it. Also,on the throttle body you will see a decal that says not to spray anything into it; disregard that! It is ok to use throttle body cleaner only! Carb cleaner "will" strip the coating! Good luck and keep us posted!

 

ok thanks....another trip to Autozone for throttle body cleaner

more later...

 

ok, started about 20 mins ago.
IAC:
--Got the IAC off and cleaned up-lots of carbon built up, might have to go buy a new one tomorrow:
Also, the 2 ports where it mounts to the throttle body look like they're carboned up quite a bit. Im a bit wary to just spray cleaner down in there...how should i clean these?

Throttle Body:
--Lifted the butterfly flap up and theres lots of carbon built up behind it. Should i remove the whole thing in order to clean it so that i dont risk getting anything in the engine, or is there a way to clean it without removal?
Just want to be safe and do it right. Thanks!