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TBirdJKC
11-17-2016, 04:31 PM
So I pulled my TB last night to replace the gasket and figured I would throw on a BBK 75mm TB I bought from a fellow member in the spring. I put it on an went for a test drive and it felt like the butterfly was binding up when closed. I thought no big deal, the idle screw is probably misadjusted. Came home, popped the hood and moved the throttle by hand and strangely enough it felt fine. I pulled the IAC connector and the engine died. So I increased the base idle a bit until it was around 450. Reconnected everything and still the same sticking. I adjusted it all the way up to 1200rpm and still sticking at the pedal. What could this be? Worn bearings, damaged butterfly?

KMT
11-17-2016, 04:59 PM
If you disconnect the throttle cable at the throttle body, does it still stick when you move it with your foot/hand at the pedal.

Using an floor mats and/or extra carpeting?

How old is the BBK?

Any carbon build up inside when you crack it open?

TBirdJKC
11-17-2016, 05:51 PM
This is definitely related to the throttle body. It did not do this with the stock one. Nothing changed with the cable, pedal, or inside the car. Unsnapped the cable from the old and snapped onto the new. The TB was pretty clean when I got it, a little oily, but I cleaned it with some TB cleaner. Mileage on TB unknown. Car has only 95,000 mi.

JonS
11-17-2016, 06:34 PM
This is definitely related to the throttle body. It did not do this with the stock one. Nothing changed with the cable, pedal, or inside the car. Unsnapped the cable from the old and snapped onto the new. The TB was pretty clean when I got it, a little oily, but I cleaned it with some TB cleaner. Mileage on TB unknown. Car has only 95,000 mi.

My BBK sticks closed a bit too. The 75mm TB is a modified mustang TB. The 70mm TBs were SC specific. The linkage had to be modified to work. On mine, that clocks the cable just enough to require more force to open.

Additionally, the 75s are designed to operate in negative pressure for the NA mustang engine. I went into mine and put the O rings on the positive pressure side of things on the throttle plate shaft. Helped vacuum and idle immensely.

Lastly, on mine, the throttle plate was not centered at all. I carefully loosened those screws and centered it in the housing. This helped the sticking and idle both

TBirdJKC
11-18-2016, 11:39 PM
My BBK sticks closed a bit too. The 75mm TB is a modified mustang TB. The 70mm TBs were SC specific. The linkage had to be modified to work. On mine, that clocks the cable just enough to require more force to open.

Additionally, the 75s are designed to operate in negative pressure for the NA mustang engine. I went into mine and put the O rings on the positive pressure side of things on the throttle plate shaft. Helped vacuum and idle immensely.

Lastly, on mine, the throttle plate was not centered at all. I carefully loosened those screws and centered it in the housing. This helped the sticking and idle both



I see exactly what you mean as at as the clocked position of the ball for the cable attachment.

As far as the pressure issue goes. I shouldn't be effected by that. Its on a N/A 5.0.

The throttle plate was way out of center on mine too. I had no idea they were adjustable. I recentered it, but haven't had a chance to drive it yet. I'll let you know tomorrow. Thank you for mentioning it! I never new it was adjustable.

JonS
11-19-2016, 07:45 PM
I see exactly what you mean as at as the clocked position of the ball for the cable attachment.

As far as the pressure issue goes. I shouldn't be effected by that. Its on a N/A 5.0.

The throttle plate was way out of center on mine too. I had no idea they were adjustable. I recentered it, but haven't had a chance to drive it yet. I'll let you know tomorrow. Thank you for mentioning it! I never new it was adjustable.

I'm curious if the idle is any different now

TBirdJKC
11-22-2016, 12:05 AM
Well I drove it and while its much improved. It still seems to stick badly when warm.

JonS
11-22-2016, 11:52 AM
Well I drove it and while its much improved. It still seems to stick badly when warm.

I don't know much about anything, but I would suspect temperature is the issue. the butterfly valve seems to be brass. I may be wrong. the TB housing is cast aluminum. they expand at very different rates with temp. I would warm it up well, turn it off, and then manually actuate the throttle closed to WOT many times. If it sticks when closed, which I think you are saying it does, the tiny little throttle plate screw can be turned in very slightly to get past the stiction point.

XR7 Dave
11-22-2016, 12:01 PM
Well I drove it and while its much improved. It still seems to stick badly when warm.

Is it a Mustang TB that has been converted to Tbird throttle linkage? If so get rid of it.

TBirdJKC
11-22-2016, 04:58 PM
Is it a Mustang TB that has been converted to Tbird throttle linkage? If so get rid of it.

Dave, I believe it is an actual Thunderbird/Cougar TB. It has SUPERCOUPE machined into the center vane on the top of the throttle body. The linkage appears to be untouched. Is there any tell-tale signs it was originally for a Mustang application?


I don't know much about anything, but I would suspect temperature is the issue. the butterfly valve seems to be brass. I may be wrong. the TB housing is cast aluminum. they expand at very different rates with temp. I would warm it up well, turn it off, and then manually actuate the throttle closed to WOT many times. If it sticks when closed, which I think you are saying it does, the tiny little throttle plate screw can be turned in very slightly to get past the stiction point.

That's what is so weird about it. I can adjust the base idle way high. Like high enough that I get a code for the ECM not able to control idle and it still sticks. If I move it with my hand it feels very smooth no matter what. I put my stock TB back on for now. Way too annoying to drive like that, but I would still like to solve this and use it.

KMT
11-22-2016, 05:14 PM
Can you take a photo of the linkage side? Closed and open if possible...

JonS
11-22-2016, 05:52 PM
Dave, I believe it is an actual Thunderbird/Cougar TB. It has SUPERCOUPE machined into the center vane on the top of the throttle body. The linkage appears to be untouched. Is there any tell-tale signs it was originally for a Mustang application?



That's what is so weird about it. I can adjust the base idle way high. Like high enough that I get a code for the ECM not able to control idle and it still sticks. If I move it with my hand it feels very smooth no matter what. I put my stock TB back on for now. Way too annoying to drive like that, but I would still like to solve this and use it.

I'm it an auto? Is the cruise control jamming?

XR7 Dave
11-22-2016, 09:56 PM
I'm it an auto? Is the cruise control jamming?

Sounds like it might be over extending the cable/cables. Disconnect the cruise to test that part of it. If that's not it, then it's possible that the throttle cable is extending too far to reach the ball on the TB linkage and might be hitting a binding spot which doesn't happen with the stock TB due to the cable operating in a slightly different range.

TBirdJKC
11-23-2016, 12:47 AM
Can you take a photo of the linkage side? Closed and open if possible...

I will try and get a pic tomorrow.


Sounds like it might be over extending the cable/cables. Disconnect the cruise to test that part of it. If that's not it, then it's possible that the throttle cable is extending too far to reach the ball on the TB linkage and might be hitting a binding spot which doesn't happen with the stock TB due to the cable operating in a slightly different range.

That's an interesting point. I don't think its over extending though. I have to push the cable back towards the firewall about a half an inch for it to line up with the ball on the linkage. But that definitely puts the cable in a different range over stock.


I'm it an auto? Is the cruise control jamming?

It is a 5 speed. No TV cable, if that's what you're thinking. I will try disconnecting the cruise cable from the throttle cable assembly and test.

TBirdJKC
11-25-2016, 03:28 PM
Here are the pictures Ken. You can see in one of them a small burr from the butterfly hitting the bore, before I adjusted it.
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TBirdJKC
11-25-2016, 10:09 PM
Since it does push the cable back slightly compared to my original throttle body. Is there anything I could do about that? The only thing I could think of is either to relocate the ball on the linkage slightly forward or make an aluminum spacer to go between the throttle body and plenum.

KMT
11-26-2016, 12:32 AM
Thanks for the photos - I was looking to see if anything jumped out about the pivot/ball angle, but nothing seems obvious. Did you by any chance remove the throttle plate and dry fire the pedal to see if it was smoother, etc.?

sam jones
11-26-2016, 02:21 AM
Good evening


Is the inlet plenum stock or MP upgrade? If stock you might need to blend the transition area. From what I understand those who have installed the 75 mm do the blending/clearing increasing to:

- Allow for more air.

- Reduce the pressure difference between the back of the throttle body and front of the plenum preventing a "vacuum lock/sticking" condition.

XR7 Dave
11-26-2016, 10:58 AM
Probably a geometry issue with the ball being a bit too far overcentered and the throttle linkage coming down toward the TB vs. a more straight approach on an SC's linkage. Little hard to tell from the pics, but you could map it if you want to know for sure.

TBirdJKC
11-26-2016, 01:54 PM
Probably a geometry issue with the ball being a bit too far overcentered and the throttle linkage coming down toward the TB vs. a more straight approach on an SC's linkage. Little hard to tell from the pics, but you could map it if you want to know for sure.

Dave, can you recommend a good way to map the throw of the throttle body that would be somewhat accurate? I've never had to do that before. I know its hard to tell from the pictures, but the BBK is definitely sits around the 3:00 to 4:00 o'clock position vs. the stock one around 5:00 o'clock. I believe this causes the initial heavy pedal feel, but not the sticking that occurs when warmed up. The ball also appears to be located slightly closer to the center of the throttle shaft vs. stock. Maybe for faster/shorter throttle response? Idk.


Good evening


Is the inlet plenum stock or MP upgrade? If stock you might need to blend the transition area. From what I understand those who have installed the 75 mm do the blending/clearing increasing to:

- Allow for more air.

- Reduce the pressure difference between the back of the throttle body and front of the plenum preventing a "vacuum lock/sticking" condition.

I thought about vacuum sticking being the issue, but what doesn't make sense to me is why it would only happen when the engine is warm. The car is a 5.0 liter with a 95 Cobra intake/plenum. I measured the plenum opening at 65mm with a caliper. So I am off by about 10mm. I haven't done any porting yet because I plan on adding some type of forced induction to the car and I'm not sure if that's the intake that will stay on the engine.


Thanks for the photos - I was looking to see if anything jumped out about the pivot/ball angle, but nothing seems obvious. Did you by any chance remove the throttle plate and dry fire the pedal to see if it was smoother, etc.?

I haven't tried pulling the butterfly completely out. Since the issue seems to only crop up when the engine is warm. I may have to pull the butterfly and warm the throttle body up with a heat gun. Since it may be a bit of an issue to start and run the car at essentially WOT. :D

KMT
11-26-2016, 04:20 PM
Since the issue seems to only crop up when the engine is warm.

Wait...what? Did I miss that bit from before?

TBirdJKC
11-26-2016, 06:45 PM
Wait...what? Did I miss that bit from before?

Yeah, I mentioned it about midway down the first page. It improved after adjusting the butterfly but still sticks when the engine warms.

FrankenBird
12-09-2016, 10:37 PM
Is the throttle blade catching on the intake? My 5.0 mn12 did and I couldn't use a 75mm tbody, until I put on an explorer intake and 75mm c&l intake elbow..it woke the car up.

TBirdJKC
12-10-2016, 12:19 AM
Running a 94-95 cobra intake

FrankenBird
12-15-2016, 11:48 AM
Running a 94-95 cobra intake

Its still only 65mm

TBirdJKC
12-15-2016, 04:51 PM
Its still only 65mm

Yeah, but the butterfly doesn't extend past the throttle body when open. And the issue was occuring when first engaging throttle.