Fox T-Bird/Cougar Forums

Technical => Engine Tech => Topic started by: youpey on June 26, 2008, 07:21:30 PM

Title: Throttle stuck??? scary
Post by: youpey on June 26, 2008, 07:21:30 PM
when driving today i found somehting happen to me that really scared me.

when driving, out of nowhere i found my car slowly accelerating on its own.

at first i thought the pedal was stuck, but when i tried to tap the gas to get it back to normal, it didnt help.
the scary part is, since it was accelerating on its own, it was very hard to slow down. finally it stopped doing it and everything was back to normal.

later on when driving home, something similar happened but it wasnt nearly as bad. i put it in neutral and the car rev'ed up to 2200 rpm's on its own.

i tapped the gas and it went back to about 800 rpms like normal

it seams when it happens i have to put it into neutral and tap the gas to get it back to normal, tapping the gas when in gear makes no difference. it stays revving on its own

it isnt constant, so i dont know if it a TPS sensor, but if anyone has any ideas, i would love some help on this
Title: Throttle stuck??? scary
Post by: dudeman351 on June 26, 2008, 07:37:49 PM
could be with the cruise control
Title: Throttle stuck??? scary
Post by: youpey on June 26, 2008, 07:38:46 PM
i didnt have the cruise on though, also, when you hit the break pedal isnt the cruise disabled
Title: Throttle stuck??? scary
Post by: daminc on June 26, 2008, 07:41:22 PM
My van used to do that. casing on the throttle cable got damaged and it started rusting inside. check it out, it may need to be replaced.

edit: sometimes they gum up when old. guessing it's original?

check the cable to make sure it moves freely first, then we can narrow things down
Title: Throttle stuck??? scary
Post by: Old_Paint on June 26, 2008, 08:30:20 PM
Umm, the ICM, if it's a 3.8, can do that for you too. It'll turn on and forget to turn back off. You don't even wanna think about buying one of those new.
 
If you have the 5.0 with EFI, it could be the IAB or IAC, which every you wanna call it. Once you open the throttle, the IAC opens fully. When you let off, it's supposed to slowly close to reduce emissions and prevent the drive-train from jerking. It's very possible that is sticking open when you're driving, and ultimately regulate idle speed. Tapping the throttle may be shaking it loose. Take it off, soak it overnight in Seafoam, then use a small plastic bottle brush to clean it thoroughly.  The one on my truck gave me the opposite problem, of sticking closed, which would cause stalling when I dropped throttle and pressed the clutch.
 
Hopefully, it is something as simple as the throttle cable. However, welcome to the realm of parts that are rare as hen's teeth. If this is your first Fox, you're gonna find it a real challenge to find parts for it.
Title: Throttle stuck??? scary
Post by: Blown306Cougar on June 26, 2008, 08:30:21 PM
it could be the idle air control motor is sticking and my need to me cleaned . allso check it see if the throttle linkage needs some lubing and or if and object is in it's way..

one other thing which you might think is a joke but it's not is check the floor mat..
it's known to wedge the accelerator pedal not under it. but on the bottom of the pedal.. it happend to me and it allso happend to Will "weasle" back in like 2003 which i warned him about it when he said he was having the same problem with the throttle sticking and at first he did'nt beleave me untill his car drove him right into a gaurd rail! and said it was the DAMM FLOOR MAT!

again how this happends is the floor mat tends to ride up the floor pan over time when your heal is placed on it when you get in the car and when you lay your foot on the pedal..
and this how the bottom of pedal gets wedged on the top of the floor mat..
Title: Throttle stuck??? scary
Post by: youpey on June 26, 2008, 09:11:25 PM
it is the 5.0 with the throttle body efi, it isnt the more modern efi that was in the late 80's birds. is this the same answers
Title: Throttle stuck??? scary
Post by: TurboCoupe50 on June 26, 2008, 11:02:33 PM
IF it only went to 2200 RPM out of gear, I doubt the throttle cable is sticking... Sounds more like the TPS or idle motor has a problem... Checked it for codes???

As for floor mats yes they can cause a problem but likely the engine would rev to the limit... BTW, I tossed my floor mat as it ain't no fun when the throttle hangs at 80+ mph(which mine did at the drag strip)...
Title: Throttle stuck??? scary
Post by: V8Demon on June 26, 2008, 11:05:20 PM
Quote
IF it only went to 2200 RPM out of gear, I doubt the throttle cable is sticking


Agreed.  I had the throttle cable stick on my long gone V6 car,  put it in neutral to get the car stopped.  The motor was SCREAMING.
Title: Throttle stuck??? scary
Post by: softtouch on June 27, 2008, 12:06:11 AM
Next time it happens put it in neutral, pull over, open the hood and check it out. See if the throttle linkage is stuck.
Title: Throttle stuck??? scary
Post by: SLEEPER T-BIRD 87 on June 27, 2008, 12:11:37 AM
bad motor mount?
Title: Throttle stuck??? scary
Post by: youpey on June 27, 2008, 08:20:27 AM
how could a bad motor mount cause this
Title: Throttle stuck??? scary
Post by: TurboCoupe50 on June 27, 2008, 09:19:05 AM
Quote from: youpey;224837
how could a bad motor mount cause this

Generally most mounts now days have a mechanical stop in the design to prevent the engine from raising more than a inch or so...

But back in the olden days, the throttle linkage would bind when the engine raised up, do to the bad mount and actually floor the pedal(I've seen them raise up 6" or more)...  Anyway it's not usually a problem with a cable setup...

I stand by my original post as the likely cause of your problem...
Title: Throttle stuck??? scary
Post by: youpey on June 27, 2008, 09:42:56 AM
Ok, i will look at that, since that should be easy to track down if it is that
Title: Throttle stuck??? scary
Post by: youpey on June 27, 2008, 12:39:50 PM
i made an appointment for next week with the garage, i couldnt figure out what was wrong with my e-brake, so i figured i would let them figure out what is wrong with the throttle. thanks guys

i will post up what they find
Title: Throttle stuck??? scary
Post by: youpey on July 02, 2008, 05:13:05 PM
UPDATE:
i took it to the mechanic today and they couldnt figure it out, but they recommended me to a mechanic right down the road that works on this type of car a lot. wouldnt you know it, it happened again on my way there. i managed to get it there with it still happening and i walked in and he looked at it right away.

the first thing he checked was the throttle cable, and that was fine, it wasnt sticking. next he looked at this circular thing with a vacuum line on it, and he determined that was the problem. he told me that is used to adjust the throttle when you have accessories on to keep the engine running, like the ac.

he told me to keep the ac off until my appointment. when i got home i tested his theory of it being the ac.

sure enough, when i turn on the ac and hit the throttle it goes all the way up to 2000 and it wont go back down. as soon as i turn off the ac, hit the throttle it is back to 800 rpms.
i am not sure what the part is called, i didnt ask him, but i can describe it
it is circular piece of metal, that looks like you cut an egg in half, meaning it is somewhat pointy on one and and flat on the other.
it has a vacuum line going to it, and there is this black bar that comes in and goes out. when the ac is on, the piece comes out, which pushes on the throttle

 
here is the weirdest part, when the ac is on, the little bar pushes the throttle out, but if i manually push the little bar back in, the throttle doesnt come back with it. when i turn off the ac, and it isnt pushing the throttle forward, as soon as i push the throttle bar, it goes all the way back and the rpms are fine

first question, can anyone tell me what this part is called. i can take pictures if the details above arent good.

second question, do you think that part is causing the issue? does it make sense that the ac would cause the issue. i rarely drive with the ac since i get headaches with car ac (all cars, not just the t-bird)

one thing i wanted to add, if i disconnect the vacuum line and hit the throttle it is fine
Title: Throttle stuck??? scary
Post by: dw85745 on July 02, 2008, 06:02:38 PM
Description  escapes me. 

Quote
next he looked at this circular thing with a vacuum line on it

If you can post a picture I can most likely tell you what it is? 
-- Or -- at least were is it located (be specific)
Title: Throttle stuck??? scary
Post by: youpey on July 02, 2008, 06:48:05 PM
here you go brother, i took 3 pics. the really close one is the part, the one somewhat further away is to show the rough location and the furthest picture is to show the location at a distance. (this is the drivers side)
(http://i46.photobucket.com/albums/f124/youpey/Thunderbird/IMG_0529.jpg)
(http://i46.photobucket.com/albums/f124/youpey/Thunderbird/IMG_0530.jpg)
(http://i46.photobucket.com/albums/f124/youpey/Thunderbird/IMG_0531.jpg)
Title: Throttle stuck??? scary
Post by: TurboCoupe50 on July 02, 2008, 06:58:04 PM
Remember I said...

Quote from: TurboCoupe50;224799
Sounds more like the TPS or idle motor has a problem...
The newer ones actually had a little motor inside them(are larger), yours operates from vaccum... Possibly can be adjusted, that's what the small hex is for on the threaded bolt below it... Could also use the bolt head on the other end...
Title: Throttle stuck??? scary
Post by: youpey on July 02, 2008, 07:45:20 PM
Quote from: TurboCoupe50;225624
Remember I said...

 The newer ones actually had a little motor inside them(are larger), yours operates from vaccum... Possibly can be adjusted, that's what the small hex is for on the threaded bolt below it... Could also use the bolt head on the other end...



good call. is this part hard to find
Title: Throttle stuck??? scary
Post by: softtouch on July 02, 2008, 08:03:40 PM
The vacuum to it is controlled by the throttle kicker solenoid. The 84 EVTM says the solenoid is on the front side of the driver's side shock tower.

(http://mysite.verizon.net/vzetk5cc/sitebuildercontent/sitebuilderpictures/CFI5.0.jpg)
Title: Throttle stuck??? scary
Post by: youpey on July 02, 2008, 10:11:13 PM
i think this is it
http://www.autopartswarehouse.com/details/QQFordQQThunderbirdQQMotorcraftQQCarburetor_Dash_PotQQ19841985QQMICD69.html
Title: Throttle stuck??? scary
Post by: dw85745 on July 03, 2008, 08:51:02 AM
Ford calls your part the Throttle Positioner Assembly.

As TurboCoupe50 pointed out, some CFI's (Throttle bodies) use a
small DC motor called and Idle Speed Control Motor) in place of the
vacuum type. 

Which came First and why Ford changed is unknown but best guess is the 1984-1987 models were transition period before full EFI.

During these years Ford also played with their heads, trying to mill them as thin a possible.  I know in 1984 Ford used a number of different production heads each different -- my guess- trying to find a balance between weight,  saving material, and no head warpage.
This was before MLS (multi-layer-steel gaskets) were used.
Title: Throttle stuck??? scary
Post by: youpey on July 08, 2008, 05:17:12 PM
i just got back from the shop, they said the problem is the egr valve and a solenoid for the egr.

he is trying to locate the parts now