TBI sensitive off idle

[thinger2]

Look at throttle shaft wear first. You will see some threads about the TBI needing new bushings.
They didnt have bushings to begin with.
If you grab that throttle shaft and try to move it up and down in and side to side you should feel zero play in it.
The steel shaft rides in the case of the throttle body and over time it wears it out in an oval shape.
This causes a vacuum leak and makes the throttle "stick" in the bore under vacuum untill it pops open.
Make sure the bore is squeeky clean too. No carbon, no burrs.
You can install brass bushings in them and cure that problem but its a little bit tricky to do it right. Not impossible at all but just takes some patience.
Look around for a place that does fuel injector cleaning and service.
Call em up and ask if they now how to bush a TBI
Call up some speed shops and talk to them.
If they know how to bush a quadrajet, they should know how to bush a TBI.
The whole bush with a rebuild kit and a warranty should be about 200 bucks tops if you find an old guy.
The "idle screw" everybody talks about on a TBI is actually an initial air stop.
Dont mess with it untill you get a real good understanding of how these work. Randomly turning that stop will lead you into a rabbit hole of tuning problems that are all caused by lack of initial air at operating temp with timing at zero and iac set and a bunch of other tweaking.
You will have to do all of that anyway, but its gotta work right before that happens

Look for grey hair and chain smoking..
Thats the guy you need to talk too.
And no matter what you do, if you have a 700r4 make sure you get the TV cable settings exactly right.
Anytime you pull a throttle body loose from a 700r4 you need to check the linkage geometry and the adjustments when you put it back together.
Dont skip this step because you can smoke that transmission in a hurry if you get it wrong

 

[PlayingWithTBI]

These guys should be able to do it too.

http://www.rvmorsemachine.com/index.html

https://www.ebay.com/str/sprperformance

 

[blue and silver 1995]

I had that problem and I replaced the throttle cable and fixed it, the bends get wore out and creates a sticky spot, I took the cable off and in a straight line it worked fine but with the big "S" it was very sticky, also clean you tbi plates with carb cleaner and paper towels.

 

[kenh]

Look at throttle shaft wear first. You will see some threads about the TBI needing new bushings.
They didnt have bushings to begin with.
If you grab that throttle shaft and try to move it up and down in and side to side you should feel zero play in it.
The steel shaft rides in the case of the throttle body and over time it wears it out in an oval shape.
This causes a vacuum leak and makes the throttle "stick" in the bore under vacuum untill it pops open.
Make sure the bore is squeeky clean too. No carbon, no burrs.
You can install brass bushings in them and cure that problem but its a little bit tricky to do it right. Not impossible at all but just takes some patience.
Look around for a place that does fuel injector cleaning and service.
Call em up and ask if they now how to bush a TBI
Call up some speed shops and talk to them.
If they know how to bush a quadrajet, they should know how to bush a TBI.
The whole bush with a rebuild kit and a warranty should be about 200 bucks tops if you find an old guy.
The "idle screw" everybody talks about on a TBI is actually an initial air stop.
Dont mess with it untill you get a real good understanding of how these work. Randomly turning that stop will lead you into a rabbit hole of tuning problems that are all caused by lack of initial air at operating temp with timing at zero and iac set and a bunch of other tweaking.
You will have to do all of that anyway, but its gotta work right before that happens

Look for grey hair and chain smoking..
Thats the guy you need to talk too.
And no matter what you do, if you have a 700r4 make sure you get the TV cable settings exactly right.
Anytime you pull a throttle body loose from a 700r4 you need to check the linkage geometry and the adjustments when you put it back together.
Dont skip this step because you can smoke that transmission in a hurry if you get it wrong

Bushing replacement kits are available all over the web for about $40 + or -
I've been messing with carbs since the early 70's. Hundreds of Qjets and TBI is not so different.
I've got the grey hair but don't smoke! LOL LOL
I grew up on throttle cables to control tran pressure. No issue there!
Well aware of the minimum idle air screw and what you can do to fine tune.

I don't want to sound over confident or arrogant but I've had a LOT of carb experience. Yes carbs and TBI are apples and oranges but a throttle body is not much more than a glorified carb. At least the mechanical part.

At the moment time or the lack of it, is my issue. Winter layoff is coming soon then I will have more time to look at and correct the minor issues.

Thank you for all the input from everybody that has contributed. All suggestions are appreciated. I understand that nobody here has a clue what my background is. Just as I have no clue what yours is. Together we can solve many problems and play off each others strengths.

Ken

 

[WILWAXU]

Check and clean the EGR while you are in there. I had a hesitation off idle, and a new EGR cleared it up.