sticking throttle

[biggsteve97]

I have a custom built 87 chevy 4x4 silverado with a 350 v8 and the last year Ive noticed the throttle likes to stick when you lift your foot of the pedal and only while the engine is running. Like when shifting gears or after being stopped at a light/sign. The throttle cable has broken three times because of this now. I replaced the throttle cable bracket to give the cable a better approach to the throttle body thinking that was it. Even swapped throttle bodies out with an extra one and the pedal still sticks. Ive checked the throttle shaft for play and while there is slight movement it is in no way loose on either throttle body. I replaced the throttle cable this last time with a lokar stainless steel and braided housing unit. When the engine is not running the throttle seems fine and when I first started the engine the throttle is fine but only for about 15-20 seconds of running. I am at a loss. If it wasnt for the fact it seems to only stick when the engine is running i would think the throttle pedal pivot is worn out. Anyone have any thoughts?
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[bilfman]

Post a pic, it will help. Also try the throttle manually by hand at the carb when it is sticking at the pedal. It lets you see what is going on and if all is good then the bind is after the carb somewhere . That's a start
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[biggsteve97]

I will get a picture and try to get it posted today. I have moved thr throttle manual at the throttle body and though I do not feel anything I do sometimes hear an audilble click type sound from around the butterflies and this was with the throttle cable both disconnected and connected.
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[INSIDIOUS '86]

What and how many throttle return springs do you have? Factory has a hard and medium spring from factory
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[biggsteve97]

I have only one return spring and it is the factory installed spring on the throttle shaft behind the throttle lever. I have had this intake/throttle body combo for atleast 9 years now and only the last year ive had problems. As of 2 months ago I installed the throttle cable and throttle cable bracket seen in the pictures below. The sticking only happens when the engine is running.

[INSIDIOUS '86]

There should be two springs that attach to the big hole on the throttle arm and run forward.
So in reality you have no return springs. This is why your throttle is sticky. Usually something like this causes accidents in the least
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[THE "10" SILVERADO]

The spark plug PCV vacuum line is a neat trick. I've never seen that done before.

[biggsteve97]

Originally Posted by INSIDIOUS '86

There should be two springs that attach to the big hole on the throttle arm and run forward.
So in reality you have no return springs. This is why your throttle is sticky. Usually something like this causes accidents in the least
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If this infact were a carburetor i would believe you on this. However, since it is throttle body fuel injection the return spring is built into the throttle body itself right behind the throttle lever. This setup looks exactly as it did they day it rolled off the assembly line in 1987 except for the throttle body spacer. I have had many tbi cars and trucks and I have never seen one with extra return springs hooked to the throttle lever itself and run forward or backward from there. If you would like to see my stock 92 Buick Roadmaster TBI 350 setup i will take pictures for you to show my truck is no different.

What do you mean by spark plug pvc trick?
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[THE "10" SILVERADO]

Originally Posted by biggsteve97

What do you mean by spark plug pvc trick?
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Your vacuum line from the PCV to vacuum port is made of a spark plug wire.

[biggsteve97]

Originally Posted by THE "10" SILVERADO

Your vacuum line from the PCV to vacuum port is made of a spark plug wire.

Ummm, no it is not. That is a 90 degree rubber elbow attached to a formed 3/8 plastic vacuum tube with a 3/8 hose on the end that is attached to the pcv valve. The smaller plastic vacuum line pelow the pcv hose is connected to the evap cannistor next to the radiator and is wrapped with the factory convoluted tubing normaly used for electrical wiring. I have no idea why GM did that and not on any of the other lines.

[biggsteve97]

Originally Posted by INSIDIOUS '86

There should be two springs that attach to the big hole on the throttle arm and run forward.
So in reality you have no return springs. This is why your throttle is sticky. Usually something like this causes accidents in the least
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That large hole you referred to in the throttle lever is actually where the stud goes for the cruise control cable. I removed it and the cruise control pod 15 years ago for easier access to the distributor connectors and because the cruise control system had long been dead by then.

I guess I should make it more clear that the throttle is sticking closed when it returns to its natural rest position. The sticking caused the cables to break.

[INSIDIOUS '86]

My hollers and quadra jets have that same spring. Still not good enough for a positive return if its sticking shut the throttle blades may be sticking in the bore. The throttle body can possibly be warped from use of the spacer
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[biggsteve97]

Originally Posted by INSIDIOUS '86

My hollers and quadra jets have that same spring. Still not good enough for a positive return if its sticking shut the throttle blades may be sticking in the bore. The throttle body can possibly be warped from use of the spacer
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Well with the 14 different TBI equipped vehicles I and my family have personally owned and none of them had any more return springs than the one on the throttle shaft with absolutely no problems with throttle return. Apparently it is sufficient to do the job. The ones I have encountered on both the holley and quadrajet carbs are insufficient to do any job let alone return the throttle to its idle position. So on the carbs I agree with you there. But we will continue to disagree on this when it comes to the TBI. Also, If you were to check out tbichips.com both customer projects and Brian the owners projects where they have pictures of the engines you will see that none of them have any other return springs than the one spring built into throttle body. Anyways, I was wondering about the body being warped or atleast the bores being out of round but the throttle only sticks when the engine is running. Is it possible there is just enough play in the shaft allowing the shaft to be pulled down slightly by intake vacuum at idle making the blades contact the bore? It only sticks at the idle position and nowhere else in the travel of the pedal.

[makman1297]

Maybe you can pull it off and see if there are any strange wear marks in the bore of it and then just wiggle it up and down and see if there is any play, if there is time to a new one. I agree, no springs off of a TBI, did you check to see if your spring broke and is maybe jamming it up. Good luck

[biggsteve97]

Originally Posted by makman1297

Maybe you can pull it off and see if there are any strange wear marks in the bore of it and then just wiggle it up and down and see if there is any play, if there is time to a new one. I agree, no springs off of a TBI, did you check to see if your spring broke and is maybe jamming it up. Good luck

There is some play but it is no worse than any other used throttle body I have or come across. It has less play than the one currently on my buick so I hadnt put much thought into it. The spring appears to be in good shape and Ive looked down the bores with a light from both the top and bottom and could see no marks at that time. it was about 6 months ago after the second cable broke so I will need to check again. Im starting to believe there is something wrong with the bores or maybe the throttle shaft is twisted allowing the blades to contact the bores at idle. Its just weird it only does it with the engine running and not when it is off. Im thinking its time to take it apart and put some bore mics in and see. After thinking about it all day and some things on this thread and others, I believe my problem lies solely within the throttle body base. Ive just never had this problem with a throttle body before so I wasnt sure where to even start.