Quadrajet Problems - Car won't slow down
Thread Starter
Melting Slicks
Joined: Sep 2000
Posts: 2,406
Likes: 418
From: Chester Virginia
Quadrajet Problems - Car won't slow down
Been trying to get my Vette to run properly. When idling the idle port screws now function, but the car will not slow down. I was checking the car out today and had a small burst up to 60 mph. When I let of the gas the car keep running 60 mph. Put the brake on to slow it down and the car would not stop when I pulled into the parking lot; full brakes and it was still moving and the tach was reading 1600 rpm. Turned the key off and quickly checked under the hood and found the carb in proper condition; primary throttle was closed and the choke was opened. Did not find anything hitting the air cleaner. I have drilled a 1/16" hole in the primary throttle plates to get it to idle and to get the idle mixture screws function. Before doing this the car would not slow down sometimes and when it would slow down it was very slow about it. The car is a 73 L-82 with a TH400. I have been fight the quadrajet for months trying to get the car to idle and run properly. Anybody have any thoughts on what to due to the quadrajet? I would like to kept the carb that I have since it is the original and am trying to kept the Vette as original as possible.
Roger
Roger
Race Director
Joined: Jan 2000
Posts: 12,399
Likes: 247
From: San Jose CA
Re: Quadrajet Problems - Car won't slow down (RMS73)
Could be that the choke's stuck open, but it sounds a little crazy. When you have a problem like that, put the car in neutral! You're really killing the master cylinder by putting so much pressure on it. Good luck w/ your problem.
-Steve
-Steve
Burning Brakes
Joined: Aug 2000
Posts: 852
Likes: 0
From: Katy TX
Re: Quadrajet Problems - Car won't slow down (RMS73)
Check the springs on the throttle return as well. They can be weak or can hang up if installed improperly.
[Modified by PatG, 12:22 AM 2/24/2002]
[Modified by PatG, 12:22 AM 2/24/2002]
Thread Starter
Melting Slicks
Joined: Sep 2000
Posts: 2,406
Likes: 418
From: Chester Virginia
Re: Quadrajet Problems - Car won't slow down (RMS73)
The carb has two new springs to close the throttles. In the garage the fast idle cam and weight lever all work very easily. When I got the air cleaner off the air valves over the secondaries were closed, forgot to verify the position of the secondary throttle plate rod, but the connection to the primary linkage on the drivers side was up in the closed position. By the way, I just turned the car off, did not shift it into neutral, It was moving about 5-10 mph when I turned it off.
Roger
Roger
Team Owner
Joined: Jul 1999
Posts: 26,545
Likes: 46
From: Huntersville NC
Re: Quadrajet Problems - Car won't slow down (ED DINAPOLI)
I had a similar problem, and most people suspected problems inside the carb. Finally, a very helpful person showed me where the linkage was getting hung up on the underside of the aircleaner assembly. Problem was, every time I shut off the engine and removed the aircleaner everything looked OK.... duh! MJ
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
Top 10 Most Expensive Corvettes Ever Sold on Bring A Trailer
Brett Foote
10 Things Every Corvette Owner Needs (2026 Edition)
Michael S. Palmer
8 Most "Only Corvette Owners Understand" Quirks and Problems
Pouria Savadkouei
10 Reasons the C6 Z06 is Still A Performance Benchmark After 20 Years
Joe Kucinski
How Much Horsepower Every Corvette Engine "LOST" in 1972
Joe Kucinski
Top 10 DOs and DON'Ts for Protecting Your Convertible Top!
Michael S. Palmer
Top 10 Most Explosive Corvettes Ever Made: Power-to-Weight Ratio Ranked!
Joe Kucinski
150 hp to 1,250 hp: Every Corvette Generation Compared by the Specs That Matter
Joe Kucinski
8 Coolest Corvette Pace Cars (and Replicas) of All Time
Verdad Gallardo
Racer
Joined: Sep 2000
Posts: 355
Likes: 0
From: Valdosta Georgia
Re: Quadrajet Problems - Car won't slow down (RMS73)
Roger, I know you said that the fast idle cam and weight moved freely, but have you backed off on the fast idle screw where it rests on the cam. also look closely at the linkage from the primary to the secondary. One part of it bends up in front of the secondary lever. Check that there is clearance in betwee the two pieces as the primary side can hold the secondary lever slightly open. Also check your centrifical advance weights in the distributor. I don't think they should create that much speed if they are hung up at full advance, but stranger things have happened. I know it's is frustrating, because all of these things have happened to me at one time or another. Barring one of these fixing it, the next thing is to disconect your linkage and plug all vacuum ports and see if it is anything with the linkage or vacuum. Hershey :confused: :chevy
Instructor
Joined: Jan 2011
Posts: 102
Likes: 1
From: St. Jacob IL
RMS73, please let me know what works for you. I've been having this same problem and I know that it's not my choke being stuck because the choke doesn't even work. It did this before and after I installed an aftermarket air cleaner so I don't think my linkage is getting hung up. Last night I checked the throttle plate and found that it was shut so my guess is that my secondaries are sticking open, perhaps?
Safety Car
Joined: Oct 2005
Posts: 3,570
Likes: 1
From: Algonac Michigan
RMS73, please let me know what works for you. I've been having this same problem and I know that it's not my choke being stuck because the choke doesn't even work. It did this before and after I installed an aftermarket air cleaner so I don't think my linkage is getting hung up. Last night I checked the throttle plate and found that it was shut so my guess is that my secondaries are sticking open, perhaps?
Melting Slicks
Joined: Apr 2006
Posts: 2,084
Likes: 14
From: Airdrie Alberta
he has a good carb forum