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I'm back after an extended hiatus. I was doing the paint and due to some personal things got side tracked for 2yrs. During that time the car rarely got started and never driven and I failed to put any staybil in the tank. Needless to say my problems began. No biggie since I was finishing the paint. Now however I have started trying to work those problems out. The car is stock except for dual exhaust. Never had an idle problem before I started the paint.
I have checked for vacuum leaks. Replaced lines in the cabin and eliminated the AC system leaks. Checked the vacuum booster and transmission--no leaks. Bad diaphragm on the egr and thermostatic air cleaner flapper. Plugged up the lines off the carb including the EFE switch. Replaced the in line fuel filter 5 times and have run 4-6 tanks of non ethanol fuel through it. I don't have the problems I had when the filter would get clogged up. I.e. Wouldn't start at all. Advanced the timing to 13* and adjusted the idle mixture screws.
I'm thinking I need to rebuild the carb but I may be overlooking something. Is there something else I should be checking first?
You adjusted the idle mixture screws with the car in either drive or reverse?
I don't think it was in drive or reverse. I believe it was in Park only because I don't recall having one of my sons out there with me at the time. This goes back about 6 wks when I tried that. I assumed it was a vacuum leak and I turned my attention to fixing those items right after I had no luck.
I would think that your idle circuit may have become plugged. Time for a rebuild.
If it's time for a rebuild, what parts should be replaced? Looks like the "rebuild kits" from Autozone or whatever are pretty much the gaskets. I ordered How to Rebuild & Modify Rochester Quadrajet Carburetors (S-a Design) by Cliff Ruggles so I guess it may say in there. It was written in 2006 and I'm not sure if we had ethanol fuel at that time which I assume makes a difference.
the idle mixture screws have to be adjusted with the car in gear and without someone stepping on the brake pedal. Place wheel chocks in front of the wheels to prevent the car from moving and if you want have your son sit in the car ready to turn it off.
the idle mixture screws have to be adjusted with the car in gear and without someone stepping on the brake pedal. Place wheel chocks in front of the wheels to prevent the car from moving and if you want have your son sit in the car ready to turn it off.
In gear? I havn't heard that before. Why adjust while in gear?
As far as the rebuild, yes it is mostly gaskets. A lot of the gaskets and parts you won't use. A rebuild is just a needle/seat, float, a couple check ball and an accelerator pump. And lots of carb cleaner.
If you read any emissions sticker where it states the curb idle speed it is done in Drive and the mixture screws are adjusted after the curb idle is established. Hover over this sample to see it enlarged. http://shop.docrebuild.com/1977Corve...sGM460126.aspx
How about that, I never thought of reading the placard that is sitting right there in front of me. What a novel idea. I will give it a try this weekend and let you guys know what happens.
Well, I just skimmed through the Rochester service manual and didn't find anything to contradict setting the mix in "drive". Emissions stickers from that era recommended not to adjust the mix-the screws are capped. That being said, I never considederd leaving the car in drive after setting the curb idle to set the mix.
I'm gonna get out an old Chilton tonight, you got me curious.
Usually a heavy dose of carb/fuel injection cleaner in the tank will eventually clean things out if you have the patience to keep running it. I tell my friends to get in the habit of pinching off the fuel line and running their car until it stalls out when they are doing big repairs. It seems that's the car sits the longest during those times.
You're right, mel...but you knew that. The old Chilton says adjust the mixture in "Drive". I have been doing it in "Park" for the last 22 years. I'm gonna do it this weekend, or Monday or Tuesday, set them my way and then set them in gear and see if there's a difference. Learn something every day!
77, you could try a can of Sea Foam in your gas. It has been known (somewhat) to be bad for cats but it might be an easy fix if you're not up for a rebuild right now. Sea Foam can be a lifesaver.
You're in Florida...jealous. I gotta put my car away soon.
10-07-2015, 09:30 PM
77 L-48 Auto, stalls at idle after warmed up
The old Chilton says adjust the mixture in "Drive". I have been doing it in "Park" for the last 22 years. I'm gonna do it this weekend, or Monday or Tuesday, set them my way and then set them in gear and see if there's a difference. Learn something every day! 