Idle Speed
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New User
Joined: Mar 2002
Posts: 13
Likes: 0
From: Alberta
Idle Speed
Hi
I have 1999 F 150 4x4 with a 4.6 auto, and i have noticed that sometimes the idle speed seems to increase to about 1400 rpm. The only time I have noticed it happen is when I am stopped at a light with the truck in neutral or when I have just put the truck into park. The truck is showing that it is warm according to the gauge on the dash (if it is actually correct) I have usually driven for about 10 mins steady. The idle will continue to stay at the 1400 rpm, then I usually just give it a tap it will go up to about 2000 rpm, then slowly go back the the 650 -700 rpm it usually idles at. I have read some of the other messages on the board and have notice the IAC could be the culprit of this idle or is it something like the O2 sensors or Throttle Position Sensor. Any suggestions would be appreciated.
Kasey
I have 1999 F 150 4x4 with a 4.6 auto, and i have noticed that sometimes the idle speed seems to increase to about 1400 rpm. The only time I have noticed it happen is when I am stopped at a light with the truck in neutral or when I have just put the truck into park. The truck is showing that it is warm according to the gauge on the dash (if it is actually correct) I have usually driven for about 10 mins steady. The idle will continue to stay at the 1400 rpm, then I usually just give it a tap it will go up to about 2000 rpm, then slowly go back the the 650 -700 rpm it usually idles at. I have read some of the other messages on the board and have notice the IAC could be the culprit of this idle or is it something like the O2 sensors or Throttle Position Sensor. Any suggestions would be appreciated.
Kasey
Hotshot
Joined: Aug 2002
Posts: 12,679
Likes: 15
From: BC, Canada
Idle Speed
I think the first thing you might want to do is get it checked for codes. If anything shows up there you'd have a good place to start. Next thing would probably be to check for vacuum leaks. It's possible though that you could have a sticky IAC or a TPS. Without testing it though you're just guessing. You could try unplugging the IAC and see what happens. If that makes a difference that could be the problem. Same with the TPS. Unplug it and see what happens. It wont run properly but you might get an indication of the problem. O2's wont cause a high idle.
Let us know what you find
Let us know what you find
Senior User
Joined: Feb 2003
Posts: 180
Likes: 0
Idle Speed
my 4.6 did the samething. then it went away for a bit, few weeks later it would not idle, then it would idle. some days no problem some days big problem. Turns out it was the IAC. I will say it was the easiest repair I have ever done. Took about 5 minutes. part from the dealer was 80.00, the price from the local autozone was 45.00. I prefer to pay a little more and use factory parts
