Sticky throttle kickdown linkage, Rochester Quadrajet.

[ClydesdaleKevin]

So I plan on tackling this tomorrow, and wondered what some of you guys thought might be the problem.

This is from my Oklahoma post, and Frank got me to thinking:

Posted on: Yesterday at 07:46 PM
Posted by: Froggy1936

"Hi Kev I do not understand why you want to remove the carb ? Any thing that is malfunctioning can be handeled with the carb mounted. Except a loose or misaligned throttle plate wich is very very unlikely !  Frank"

And my reply:

"Hey Frank,

I'm not sure if I'll have to remove it...I'll try with a small mirror first to see behind the choke assembly and down to where I think its sticking...but its really hard to see in there...it appears to be sticking underneath the linkage, between the choke body and carburetor body.

Removing it would be the last resort, if I can't get a visual of where its rubbing with a mirror, or if where its rubbing might have to be filed down a bit, I'd have to remove it.

I had another thought, based on your throttle plate suggestion, but its a long shot.  When they gave me back the rebuilt carb to install, they base gasket was a little different than the base gasket that was originally on the carburetor.  The original base gasket has just one big hole cut out of it, with rounded out openings for the 4 individual barrels.  Picture 2 sets of Mickey Mouse hats, with the hat part placed against each other, and that is sort of what the cutout hole on the original base gasket looks like.  The new base gasket has 4 individual holes, exactly the same size as the barrel openings under the carb.  2 smaller holes in front, 2 large holes in back.  Do you think its possible the valves are rubbing ever so slightly on the base gasket, just enough to prevent the throttle from kicking down?  I saved the original base gasket, and if that ends up being the case, I can take it down to an auto parts store and see if they can match one up for me.  Or I could slightly trim around the opening of the new base gasket if its rubbing."

So what do you guys all think?  If I can't figure it out with the mirror, I'm thinking of removing the carb, and putting the original base plate gasket in place, tightening it down, and seeing if the linkage still sticks.  That would at least let me know if its the new gasket or not.  If it is the gasket, I could either trim in a bit around the holes, or take the old gasket to an auto parts store and try to get a new one that matches.

Any other suggestions on what to look for when troubleshooting the sticky linkage?

Thanks guys!

Kev

[Froggy1936]

First what exactly is the problem (sticky usually means sticking at high idle)  The gasket with the 4 holes is the correct one But it could be for a carb with smaller bores You should be able to look down the bores with a strong light and see if there is any interference at the gasket before removing. Make shure engine is cold to stop vaporization of fuel (makes it harder to see) Also have a helper to hold throttle open with acc pedal to see linkage operating flooding and a hard start will occur. force holding choke open will allow secondarys to operate unless they are vacume controlled then you will need a vacume pump (hand held) To supply control A book would be a big help with lots of pictures  (like the one i mentioned before)  Or you can post photos of problem and see if it can be diagnosed on line  Frank

[ClydesdaleKevin]

All figured out!

So it was sticking open on high idle.  I removed the choke and choke housing to see what was going on, and after much trial and error, and a small mirror and flashlight, I determined it was definitely being held open by slightly sticking on the fast idle cam...just slightly, but enough so it would hang up there.

I tired adjusting the fast idle screw, but that did nothing but make it run wonky with hesitations.

So in order to use my choke, AND have the idle kick down properly, I started playing with the choke adjustment with the engine warm.  A little bit at a time, turning it clockwise to put less spring tension on the butterfly valve...and voila!  It kicks right down by itself.

But then there was a flat spot from idle to acceleration.  A call to my mechanics and that problem was solved...the green lever that pushes in the accelerator pump wasn't making contact with the piston...so a slight bend, and now its fine...although I do need to spray some PBBlaster down in that piston...it doesn't return nearly as fast as it should...mechanic said it was the new seals, so spray it and work it a bit, and it should free it right up.

Tomorrow morning I'll start her up and make sure/hope that the choke actuates properly...otherwise its some more tinkering, but at least I know what it is now and how to fix it!

MAN these things are a juggling act!  How all the systems and adjustments are so interrelated you have to find just the right balance for everything to work right.  Geesh!

Oh yeah....and that little rod that goes down into the carburetor body, that engages that flat piece of metal that engages the choke shaft?  Yeah...I REALLY hate that thing...   It took me the better part of an hour to get it lined up just right with the choke.  Oi vey!

So it appears to be fixed completely, but I'll know for sure if the choke is working correctly tomorrow morning, and I'll know for sure if everything else is working right when we head to Kentucky...lol!

Kev