Quadrajet Problem Solving > Diagnose a Quadrajet carburetor problem
Idling Too High
Cliff Ruggles:
You need to get the throttle plates fully closed, indexed and seated.
The problem is most likely the linkage. Not uncommon to have to do some "tweaking" to get them fully closed and open to 90 degrees at WOT.
I've rebuilt tens of thousands of them and almost all of them require some attention in that area to work like they are supposed to.
I offer a service to rebuild baseplates if you can't figure it out and want bronze bushings installed......
Zach:
--- Quote from: Cliff Ruggles on February 15, 2023, 08:51:29 PM ---You need to get the throttle plates fully closed, indexed and seated.
The problem is most likely the linkage. Not uncommon to have to do some "tweaking" to get them fully closed and open to 90 degrees at WOT.
I've rebuilt tens of thousands of them and almost all of them require some attention in that area to work like they are supposed to.
I offer a service to rebuild baseplates if you can't figure it out and want bronze bushings installed......
--- End quote ---
Thanks for the response. I am pretty limited on tools and knowledge, but I'll take a stab at it. I will most likely need to ship it out to you. We will see.
Thanks again.
Kenth:
Adjust pri to sec link as follows:
Open pri throttle some and when #1 meets the sec shaft arm (do NOT bend top of arm) #2 should be in center of slot. Bend link on throttle blade side for proper position.
Open throttles to WOT adjust #3 for close to 90° opening of the sec throttle blades.
Fully close throttles adjusting closing tab #4.
Done!
Zach:
Update, got the throttle plate back from Cliff and it feels more solid.
Issue still remains, no change in performance from before and after the rebuild. I have a vacuum leak somewhere and I cannot find it. Putting my hand over the primaries and completely suffocating it causes no change in idle speed or anything noticeable. Making around 16 vacuum at 1000 rpm. Curb idle screw completely out, idle mixture screws set to the best I can get at the moment 3ish turns out. Only places I can think of are bad gaskets on the carb, they are brand new. Brake booster, brand new, but I can try disconnecting it from the vacuum and plugging it. Intake manifold gasket has been on there for a while, I can try spraying more carb cleaner later. Spraying carb cleaner anywhere else doesn't reveal anything, I've replace most things on it, vacuum lines, PCV valve, etc. not sure what else to do.
Zach:
Anyways I did some more playing around, high idle cam was hitting a small bit but I fixed that, but it didn't solve any issues. I think I'm past vacuum leaks, hand over carb does in fact kill it. Now I am wondering if it is a timing issue, still set to 18 BTDC at 1k rpm using the factory vacuum line routes, manifold vacuum from carb through the emissions check valve. Or something is wrong with my idle circuit and it is dumping too much fuel or air. It was a stock rebuild and clean, I didn't add any hop ups, like jets, or idle bypass, etc. Just to restate it, curb idle screw can be completely unscrewed (transfer slot can only be seen a little bit), and the car will still run at 1k rpm 18 vacuum pretty steady.
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