fast idle on HO motor

[JD's Toy]

just like the topic says, i've got a fast idle condition on my 1986 wagon with an HO swap. i've diagnosed it to either the TPS or the throttle body butterfly itself. expect it's the throttle body butterfly.

if i start the car up and it's warm i get idle at 1500 rpms. i can pop the hood and push the TB linkage closed by hand just a touch and idle drops down to 900 or so rpm (or perfect in other words). if i go hit the gas pedal and let go idle will settle back out at 1500 rpm unless i go back under the hood and manually "close" the throttle body butterfly.

when at 1500 idle TPS voltage is like 1.08 volts. When at 900 rpm TPS voltage is 0.98 volts. It seems like the return spring on the throttle body butterfly almost isn't strong enough or something, but that seems kinda kooky.

When in gear it always idles at about 900 rpm.

questions:
How in the F do i make the throttle body close all the way? I'm sure it's not closing because i can plug both the IAC port and small hole in the TB blade with my fingers and it still runs. Then if I push the throttle body butterfly closed with my hand it dies immediately. I mean it must just be open a crack, but with the diameter of the thing i guess its pulling some good air through that crack. The thing is about as shiney clean as clean can be after a bunch of air intake cleaner and scrubbing. There is space between the mechanical stop on the TB and the linkage. thinking about it now, could the transmission TV cable be holding the throttle open slightly somehow?

thanks everyone and look forward to some ideas!

[mrltd]

is any of the linkage binding? The throttle cable or TV cable?

[gadget73]

sounds like the linkage is binding to me too. Try unhooking the throttle cable and see if it continues to do this. Might be your throttle cable or the cruise cable is binding or bad. The TV cable wouldn't likely do this but I suppose anything is possible.

[JD's Toy]

10-4, i'll check if the linkage is binding tomorrow. i expect i'm not going to get that lucky, but who knows!

not that big of a deal for me to have high idle, but since i know how to fix it by pushing on the linkage seems like something i should at least attempt to fix.

i appreciate the prompt replies!

[Pirate]

Something else you might want to try?

Get some throttle-body cleaner, and with the engine turned off, clean the throttle body from the inside, with the throttle valve open. There may be some gunk between the throttle blade and the body, preventing the blade to close all the way, unless you push it closed.

Just a suggestion...

[cld783]

Something else you might want to try?

Get some throttle-body cleaner, and with the engine turned off, clean the throttle body from the inside, with the throttle valve open. There may be some gunk between the throttle blade and the body, preventing the blade to close all the way, unless you push it closed.

Just a suggestion...

also hose down the return spring with carb cleaner then give it a shot of pb blaster.. or wd-40 whichever you prefer.

[JD's Toy]

y'all are genious's! mrltd and gadget get the golden calipers although the other suggestions were good ones.

cruise control cable was bound up on me so the throttle wouldn't kick fully closed. all is wonderful again! in park i idle around 800 rpms, in gear i'm at 600 rpms.

glad it was something so simple this time. i was able to fix it in 5 mins with a screwdriver and flashlight before coming into work this morning. Sometimes you just need the help of others to point out something obvious you're missing!

thanks again! if i lived closer i'd buy ya cookies and beer. mmmm cookies... mmmm beer....