when i get to lights, or slowing down in neutral, the truck wants to idle at about 2k, i used to b able to tap the gas lightly and quickly, and it would go down, but now it doesnt.. i was gonna try and get some graphite or silicone lube today at work and spray that on all the moving parts of the throttle cable..

anyone have any other ideas on why it wants to idle so high?

also, once i get it below 2k, it stays there until it gets above it again then wont go below on its own, unless im engine braking.

Thanks
-Matt

 

does it always idle high or just sometimes?

 

not when i first start it, but once i start driving yes.. i havnt hit the trails in a while, only pavement, so idk if it would happen off road or not..

 

Most likely you have a carbon buildup on the throttle body and/or throttle plate.

Buy a can of cleaner called "throttle body cleaner". It looks exactly like carb cleaner but it's specific to throttle bodies. DO NOT USE CARB CLEANER because it can/will disolve a coating that's on the TB.

Take your intake elbo off and using a tooth brush with the can of spray cleaner disolve the carbon on the inside of the body and both sides of the throttle plate.

The motor may hesitate when trying to start after you put it back together. Don't worry just keep cranking for 10-15 seconds (max) to get it started.

It'll only cost you $5 at the most and I'm 95% sure this is your problem.

Rich

 

It is normal for the IAC to slowly close down the RPM on decel. This is the dashpot function and it helps prevent hydrocarbon spikes when the throttle plate is suddenly closed and the vacuum jumps up.

If it is hanging longer than it should like yours seems to be, there are three common causes:

IAC valve is sticking open
TPS voltage is too high with the plate closed (0.50v~1.25v is normal)
Throttle plate is sticking open


**Edit** Here are the meanings of the acronyms above:

IAC = Idle Air Control valve
TPS = Throttle Position Sensor

 

i have taken my throttle body off, cleaned it, and my whole upper intake plastic thing ( i forgot the name)


so yall r saying its not that the throttle could be sticking? and what coating is on the TB? i think i used tb cleaner :( i tried not spraying it directly into the tb though..

 

It looks like at least two of the posts above say that the throttle plate might be sticking.

There is a gray/black coating in the bore or the throttle body and around the edge of the throttle plate. Don't remove it.

 

i was in a hurry... :(

 

LOL.. well you need to do this.

Fords typically since the 90s have had two issues when it comes to symptoms like you mention.

1) TB carbon build up where the TB plate closes off in the bore. (most any brand of car does this)

2) The idle air by-pass valve gets dirty and/or does'nt work properly.
The old 5.0L motors and a lot of the early 4.6L motors had problems with them.

I went back and re-read your initial post. If the rpms don't come down at all.. once you clean the TB (inside) really good.. and it still does this? You might look for a vacuum leak. I'm not to sure if a vacuum leak would throw an engine code on your year of truck?

Rich

 

i think a vacuum leak would throw more off wouldnt it? miss fires? gah, bc it DOES go down... sometimes, its not like its preminetly stuck above 1500...if im like engine braking though, it will jump back up to 1500-2000 whn i push the clutch.

im gonna go out and wash/wax my truck, then either do xmas lights or mess w/ my TB...

-Matt

 

had your problem on my 2001 mazda b2500. put off fixing because I got a cel code, egr problem. played around with the egr valve and assorted vacuum lines, didn't find anything but the cel went out so put it back together, fired it up, waited for the pcm to catch up, everything ok called it fixed. Hours later I realized that my idle response was back to normal, go figure. I'm no mechanic, not even close but it must have been those pesky vacuum lines I re-did. What ever, maybe get you on a different path of checking,: or not LOL.

 

stakreutermazda, You do realize you're replying to a 15 year old thread and to someone that hasn't been here in 9 years.