Cold Start Fast Idle Question
Thread Starter
3rd Gear
Joined: Jun 2011
Posts: 3
Likes: 0
Cold Start Fast Idle Question
Got a 77 L48 that idles to fast for my comfort when started cold. it jumps to about 1700 rpm. i adjusted the idle while warm down to a loafing 650. i prefer my idle to be low to decrease the impact on my tranny.
after you start it... you can kick it down after about 2 minutes. and it will run pretty the rest of the day. im a little worried about not giving my fluids enough time to circulate before running it wide open. what can i do to slow the sucker down on a cold start? no idle problems when it warms... that is the reason i havent already been replacing vacuum hoses like crazy already.
should i still be looking at the vacuum system?
any help would be greatly appreciated.
after you start it... you can kick it down after about 2 minutes. and it will run pretty the rest of the day. im a little worried about not giving my fluids enough time to circulate before running it wide open. what can i do to slow the sucker down on a cold start? no idle problems when it warms... that is the reason i havent already been replacing vacuum hoses like crazy already.
should i still be looking at the vacuum system?
any help would be greatly appreciated.
Le Mans Master
Joined: Aug 2006
Posts: 7,431
Likes: 1,561
From: mount holly NC
2025 c3 ('74-'82) of the Year Finalist - Unmodified
2019 C3 of Year Finalist (appearance mods)
Do you have a Q-Jet?
On the passenger side of the carb there is an adjustment screw have tried that?
Team Owner
Joined: Jul 2008
Posts: 23,419
Likes: 22
From: In limbo
St. Jude Donor '13-'15, '17 thru '22
What kind of carb is on your car? What kind of choke is it using, if any?
Most carbs on street cars from this era use some kind of choke, reducing the air intake and increasing the idle when the engine is dead cold. After a warm-up period, the idle should return to normal, and it sounds like it is. A cold idle of 1700 sounds pretty high, I think 1200 would be more normal for a car that idles well at 650 when warm, so it sounds like you might need a choke adjustment.
Most carbs on street cars from this era use some kind of choke, reducing the air intake and increasing the idle when the engine is dead cold. After a warm-up period, the idle should return to normal, and it sounds like it is. A cold idle of 1700 sounds pretty high, I think 1200 would be more normal for a car that idles well at 650 when warm, so it sounds like you might need a choke adjustment.
Thread Starter
3rd Gear
Joined: Jun 2011
Posts: 3
Likes: 0
its the stock 4barrel carb... I cant remember off the top of my head what they put on there oem... rochester maybe? just a guess. I bought this car back in the summer and just finished a complete trailing arm rebuild. there wasnt but 43000 originl miles on it... well documented too.. pretty good find for the price I paid. anyone got a reference to where I can read about adusting the choke correctly?
thanks for the help
thanks for the help
Drifting
Joined: Mar 2011
Posts: 1,886
Likes: 9
Got a 77 L48 that idles to fast for my comfort when started cold. it jumps to about 1700 rpm. i adjusted the idle while warm down to a loafing 650. i prefer my idle to be low to decrease the impact on my tranny.
after you start it... you can kick it down after about 2 minutes. and it will run pretty the rest of the day. im a little worried about not giving my fluids enough time to circulate before running it wide open. what can i do to slow the sucker down on a cold start? no idle problems when it warms... that is the reason i havent already been replacing vacuum hoses like crazy already.
should i still be looking at the vacuum system?
any help would be greatly appreciated.
after you start it... you can kick it down after about 2 minutes. and it will run pretty the rest of the day. im a little worried about not giving my fluids enough time to circulate before running it wide open. what can i do to slow the sucker down on a cold start? no idle problems when it warms... that is the reason i havent already been replacing vacuum hoses like crazy already.
should i still be looking at the vacuum system?
any help would be greatly appreciated.
Play with it. That's why we have these beasts in the first place. Make your adjustment and then say, "Honey, I need to go out for a test drive, I'll be back in a little while".
Instructor
Joined: Sep 2010
Posts: 229
Likes: 2
From: Grants Pass Oregon
Got a 77 L48 that idles to fast for my comfort when started cold. it jumps to about 1700 rpm. i adjusted the idle while warm down to a loafing 650. i prefer my idle to be low to decrease the impact on my tranny.
after you start it... you can kick it down after about 2 minutes. and it will run pretty the rest of the day. im a little worried about not giving my fluids enough time to circulate before running it wide open. what can i do to slow the sucker down on a cold start? no idle problems when it warms... that is the reason i havent already been replacing vacuum hoses like crazy already.
should i still be looking at the vacuum system?
any help would be greatly appreciated.
after you start it... you can kick it down after about 2 minutes. and it will run pretty the rest of the day. im a little worried about not giving my fluids enough time to circulate before running it wide open. what can i do to slow the sucker down on a cold start? no idle problems when it warms... that is the reason i havent already been replacing vacuum hoses like crazy already.
should i still be looking at the vacuum system?
any help would be greatly appreciated.
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
5 Best & 5 Worst Corvette Daily Drivers
Joe Kucinski
The Headlights of Every Corvette Generation Explained
Joe Kucinski
5 Best & 5 Most Overrated Corvette Track Packages of All Time!
Joe Kucinski
Every 2027 Corvette Engine Explained
Joe Kucinski
Designer Imagines A Corvette That Looks More Like a Corvette Than the Corvette
Verdad Gallardo
10 Ugly Corvettes That We Still Kinda Love
Joe Kucinski
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
Drifting
Joined: Oct 2009
Posts: 1,939
Likes: 199
From: Palm Bay Florida
1700 sounds about right or it will stall on cold start in cold climates. You can set it lower if you dont mind stalls those specs were for when we drove these cars as daily drivers.
Mark Napoli
Mark Napoli
