Hey guys, I need some suggestions or opinions please. I have an 86 IROC with a 383 stroker TPI. When the car is off, the gas pedal is real easy to push down and even under the hood the throttle lever is easy to pull back and hits the set screw every time. But it's a different story when the car is running. If I push the thottle down it stays there, doesn't kick back without me giving it a quick rev. I've sprayed WD-40 over everything to try and find a vacuume leak and got nothing. I also disconnected the cruise control cable and vacuume hose and still same thing. I'm at a loss, I've set the IAC and TPS so many times I've been doing it in my sleep. I just don't know what it is because like I said it moves freely when the engine is off. Any ideas before I go bald ripping my hair out?

 

Just a guess...

It could be that your engine draws a powerful enough vacuum at idle to force the throttle blades open slightly. You might have to add an additional throttle return spring. It is a pretty easy thing to do -- you just have to find a spot to mount the end and then make sure the spring doesn't bind on anything throughout the travel of the throttle.

 

The throttle shaft is offset slightly so that vacuum will actually draw the blades closed, not open.

 

Thanks for the replies guys, since that can't be it, any other suggestions?

 

Remove the boot in front of the throggle body. Spray a good lube to the left and right of the throttle blades. I used wd40 and it still stuck a bit. Then I used liquid wrench and it opened and closed very easily.

 

I'll try that trick, but I took the TB off two weeks ago and cleaned it all out, plus it's only hard to operate when the car is running. When it's not running it opens and closes realy easy.

 

Don't give up on the throttle return spring too quickly. If I am understanding your symptoms/description correctly (?):

*Throttle closes completely with no problem with engine off (this seems to exclude lack of lubrication)

*Throttle remains open with engine running

*Throttle remains closed when pushed closed while engine is running

The slight offset sounds like it is not coming into play until some critical angle of throttle opening. Until (and before) that point is reached the vacuum of the engine is overcoming it and keeping the engine running too fast. A throttle return spring would get you past that critical angle by overcoming the force of the vacuum while the engine is running.

It's a simple thing to try. Cost you maybe a dollar or two?

 

Felo, that's exactly what happened to me!
I cleaned the thing out and it caused it to stick..and yes, only when the car was running. Trust me, lube up with a good lube..especially to the left and right of the blades and it'll work!

 

No offense, Steve, but if the throttle return action is that borderline on a car, an extra throttle return spring is a good safety item. The stock return springs on the TBI, like with carbs, weaken with age.

 

No offence taken.
Are we talking about TBI here? I thought you had a TPI?
Anyways, after I gave my TB a real thorough cleaning I must have driven all the lube out too.
I lubed it up where I said and it snaps back very nicely now. A helper spring would definitely help, and I was 2 seconds away from installing one until a buddy mentioned the inner side of the throttle blades.

 

Yes, you're right: 'TPI' rather than 'TBI'. Same issue, though.

I'd still add another spring because that sure sounds borderline. Many race orgs require dual throttle return springs.

You're right about WD-40; it was only designed as a water-dispersant.

 

Thanks Kevin and Steve, yes it is a TB for a TPI. After you lubed it up did you ever have that problem again? And would it be beneficial to take it off of the plenum and lube the entire TB, then put it back on? Or should I just do it while it's running? Last question Steve, will the PB Blaster hurt anything spraying into the TB? Thanks for all the help.

 

Turn the car off. Remove the boot and lube it. Put the boot back on and start her up...if it's still bad, install a heper spring. The only time I had the problem again is when I used TB Cleaner all over it 2 years later. Fixed the same way..a little lube.

PB Blaster?

 

PB Blaster is another brand of penetrating oil. Look at the manufacturers label for their recommendations. If they have a deleterious solvent (usually for plastics/rubber) they should call it out. Doesn't seem likely though.

 

The PB Blaster is something I read from a previous thread, sorry. So WD-40 isn't the lube to use, I'll buy another lube then. Thanks again.

 

Steve, all I got to say is you da man! The lube trick worked perfectly, now I can drive around town comfortably. Thanks!

 

Glad to be of help.

 

Anyone have any pics of a helper spring installed? I've been hearing about it more and more.. just wondering what it looks like..

 

Hey guys, I have the same problem with my throttle sticking. I just installed a new ported plennum and slp ported runners. Well when i was swithcing the plennum i had to take off the TB and I cleaned the hell out of it , now it sticks only when driving, but when i give the throttle a little jolt the rpms come back down to normal. I'm heading out to the garage now to try the pb blaster trick, This board is excelent!!!! thanks guys

 

blaster worked great!!!! saved me some money thanks, andy