Hey everyone,

I have a 1999 f150 with a 4.6 motor. This only happens when it is very cold out like below 32 degrees F. I get in the truck turn the key the truck fires instantly but instead of running on the standard cold high idle it dips down to about 600 to 900 rpm and after about 10 to 15 seconds it jumps back up to a high cold idle. other than this little issue it runs like a top without any problems at all. This truck has about 84,000 miles on it. The fuel filter and plugs have been changed within the last 10,000 miles. Any help would be greatly appreciated. I did a search and could not find anything like this for a 99.

Andrew

 

anyone have any ideas

 

I was hoping someone had an answer. My truck is doing the same thing but doesn't start unless I give it gas when it fires. When the outside temp is warmer it's better. I did some more searching and it sounds like the IAC needs cleaning or replacing. Sooo what is the IAC and where is it located? Do I sound like a newbie?

 

in the 4.6 its right on the top of the throttle body. its small round cylinder ,two bolts and it comes off. im sure others can send some pics.

 

Not trying to jump on your thread but my 99 f150 was doing about the same thing and I cleaned the MAF sensor and cleaned the throttle body where the air intake goes into it and it runs much better. There was a lot og gunk built up in the opening of the trottle body where the flap would move. mine has over 200,000 now running smooth again. good luck

 

hey keith97xlt,

With the iac can you clean them or do you have to replace them. I was also thinking of giving the TB a good cleaning also. What do you use to clean the MAF? Thanks for the info I really appreciate it.

Later,

Andrew

 

is the iac located in the same place on the 5.4 as the 4.6? What is the iac and what does it do?

 

Add me to the list! Same exact symptoms, only under 35C and gets worse as it gets colder. Looking forward to finding a solution. 2000 F150 with 4.6L engine. (And I don't know what the IAC is either...)

 

IAC= idle air control. From my past experience, on the 5.4 it is on the rear of the throttle body/elbow. Its wayyyy back there. Not that hard to remove. Take off the plastic cover on the throttle body (3 bolts) and look back there. I did one for a friend 4 days ago. Take off the 2 bolts, be careful not to rip the gasket.
There is a small wire harnss connector on it with 2 wires. I found it easiest to do the 2 bolts, then slide ot to the drivers side and then undo the connector.
Icleaned his out with some carb cleaner and moved the small shaft in it with a small screwdriver back and forth . Its still working great right now.
Some will say to just replace it. I can't argue with that. My friend wanted to try to clean it first. I have just got a new one for mine in the past. About $75.
Its a common problem on most of the cars/trucks out there.
I hear a cleaning may get you one or two more years.

On the 4.6 liter its on the side of the throttle body. Much easier to get at.
bullseye670..........................

 

hey everyone,

Just an update, I cleaned the IAC and the throttle body and the truck is running 100% better than before. The IAC was really nasty inside so I cleaned it with carb cleaner, wd40 and compressed air. I cleaned the throttle body with stp throttle body cleaner. With the throttle body i sprayed the butterfly plate really goob and scrubbed it with an old tooth brush then I open it and sprayed the backside of the plate and scrubbed it and then I cleaned the seating/sealing surface in the throttle body. I should have removed both the throttle body and the elbow that is between the TB and intake manifold but it was very cold and windy, so if this gets me through the winter and into warmer spring weather then I will take everything off and give it a really good cleaning , but for now she runs great.

Andrew