RESOLVED, see post 4

hello everyone.

I have a 79 Trans Am with a significantly modded 403 engine and I have a problem you may be able to help me with. Since it is Olds Powered ||I thought I would look for help here.


I have just experienced something a bit scary. I fired up my Trans Am and went for a drive. About 30 minutes in, I stopped for a red light and once it turned green I drove off. Well the throttle on the q-jet stuck open on me.
I tried "tapping" the gas pedal and it did not help, in fact it caused the RPMs to climb and stay high. I was able to get the car safely stopped and shut off.
( boy did it not like shutting down at 3000 RPM)

Anyway, I got it started and was able to idle it home to my garage. This is what I have found.

The Carb is clean on the outside as I keep it clean.
The return spring(s) are good - I even tried the set from an Q-jet I had laying around
The front choke pod is functioning as when I disconnect the vacuum lines it closes
The throttle cable seem to slide freely both directions
All the smaller diameter Vacuum lines are new.

After removing the air filter and housing, and changing the throttle return springs it seemed to return to idle with no problems. sitting in park and blipping the throttle it returned to idle.
I hopped into the car to see if it had improved ( without the shaker and air cleaner assembly on it )and it was fine.....for about two blocks of driving and then the throttle began to stick again.
I stopped the car hopped out, pushed the throttle back to the idle position and crawled back to my garage

What I have found I guess is the part of the carb that pivots to close the throttle won't return to the Idle position without some manual force to get it there, it doesn't return to the idle stop unless i push it there with my hands.

any suggestions on where to start to look for issues or any solutions you may have are greatly appreciated.

 

Unhook all the cables that go to the throttle arm, feel for any binding or sloppiness.

 

Yes, you need to isolate where this problem is occurring.

If it is the carburetor itself, this is NOT a usual problem, so there is no "canned" solution. You need to figure out what is hitting what, and then make that stop happening, which may involve filing or bending something.

If you narrow this down to the carburetor, and you can't see anything binding on any of the linkage, then the carb. has to come off so you can see whether any of the plates is sticking on anything beneath it.

- Eric

 

I found the problem, a nylon zip tie found its way into the primaries of the Q-Jet and were keeping them from closing
Somebody ( me ) needs to be more careful when removing these things as I likely cut one off tossed it onto my bench and into my Blockers Shaker then when I put it back on the small tie likely fell into the primary of the carb.

http://www.blockersperformance.com/products.html

 

Well least it was something simple and it did not make its way into the engine.

 

That was easy.

- Eric

 

Glad you found the problem.

Nice looking T/A

I know the feeling when the throttle hangs wide open like that did. Definitely a "pucker" moment to say the least.

 

I had a 77 403 powered Riviera that would go full throttle when you would try to engage the cruise control.

A bit hairy the first time around ...

But it became a rather entertaining quirk after that.