Corvette C3 Forum 1968 through 1982

78 carb idling higher slowly

Old Mar 9, 2025 | 03:42 PM
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Default 78 carb idling higher slowly

Hello everyone I just recently just bought a 1978 corvette sliver anniversary edition I put on a spectre 14 inch open air cleaner and it went on perfectly it was sealed nicely and I went to start it start but the idle began to idle up slowly it got 2500 then I shut it off and left it alone to ask people who would know more this is my first corvette and my first old style car any info will help
 
Old Mar 9, 2025 | 06:03 PM
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It sounds like it's on the high idle cam, was your engine cold? If so blip the throttle and that will bring it down a little. At takes a couple of minutes to warm up to the point of idling normally. Rather normal on carbureted engines with automatic choke.
Welcome from Washington!
 
Old Mar 9, 2025 | 06:10 PM
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Default See if it was the automatic choke

Thank you for the advice I did originally start it cold and so went out again I let it idle for 5-10 minutes and blip the throttle and it went up to 2700 I do have a bad fuel / air mixture a little misfire because the spark plug needs to do but i didn’t think adding a new air cleaner would affect the car could those problems be something to do with that?
 
Old Mar 9, 2025 | 07:50 PM
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Air cleaner will not cause that unless it's interfering with the throttle linkage.
Take it off and start the car! If it behaves like it should than you need a spacer under the air cleaner.
It's also a good time to check the throttle linkage for binding and maybe give it some lube.
 
Old Mar 9, 2025 | 08:59 PM
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Alright thank I will check it out tomorrow and i will let you know if its fixed thank you
 
Old Mar 10, 2025 | 06:22 AM
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Welcome to the forums. And welcome to carburetion,
 
Old Mar 10, 2025 | 11:49 AM
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Welcome to the forum. You can also try putting the original air cleaner back on and see if that has any effect on the idle.
 
Old Mar 10, 2025 | 05:25 PM
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Default Take off the cleaner all together and putting in the stock one

Thank you everyone for the help I took after the air All together it still did it so I put the stock one on and it went back to the wall it was originally so I guess it’s fix I think it was the combination of the misfires with the bad fuel / air mixture then adding the high flow to it
 
Old Mar 10, 2025 | 07:22 PM
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I'm inclined to side with Thomas on this one. I think your new air cleaner housing is hitting the linkage someway. Easy way to tell would be to take the air cleaner off and start the car and let it warm up to where it idles normally and then without turning it off, set the new air cleaner on it and button it up. If the idle doesn't change, then throttle it up to around 2000 RPM and then release it and see if it goes back to the idle speed.

Did you put an entire new air cleaner housing and all on it or just a different filter?
 
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