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nj7000
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When I start up my 78' Coupe, especially on cooler days, it likes to idle really high until the engine heats-up. Is it supposed to idle so high for 5 minutes almost? thanks,
Nate
Nate
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The car is supposed to idle higher than normal at startup, that's the function of the choke. When you push the gas to the floor once, it engages the choke. How high is it idling?
I'm sure someone here had a pretty detaile scientific reason but I always understood it to simply be a way of keeping a cold car from stalling at startup at low RPM and getting the engine warmed up.
I'm sure someone here had a pretty detaile scientific reason but I always understood it to simply be a way of keeping a cold car from stalling at startup at low RPM and getting the engine warmed up.
Eddie 70
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I posted a similiar question not too long ago and got this answer. Here is a link to the question.
http://www.corvetteactioncenter.com/forums/showthread.php?postid=150596#post150596
http://www.corvetteactioncenter.com/forums/showthread.php?postid=150596#post150596
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Rich80
Guest
Mine idles at 1200 to 1500RPM for about 5 to 8 minutes on a cold start. I can kick it down after that by punching it. She idles normally at about 600 RPM.
The fast idle screw can be adjusted. What could be happening though is that the choke housing is rotated towards the richer side (look for arrow of direction and marks).
The choke plate creates an increase vaccum below, so the vaccum forces fuel from the idle and main metering systems. The choke housing controls the amount of vaccum (by controling the choke plate position) and therefore the amount of A/ F ratio (to an extend). So the fast idle screw has to be "balanced" with the choke housing adjustment to really set the best fast idle speed. I did check for specific fast idle speeds, and those can be found in the appropiate manufacturers manual for the specific year/model of vehicle. Maybe that is why I have not found in any of my carburator books the suggested speed except that it should be sufficient to surpass cold cracking forces exerted by oil viscosity and the like.
The darn thing is required, for the vaccum levels produced by your average 50 - 70 rpm cranking speed is not sufficient to get the idle and main metering systems to operate. However, all this effort is rooted in the lack of appropiate fuel atomization when the engine is cold. EFI has one up on carburation on this issue alone. You can start an EFI engine and get going in seconds if needed.
The choke plate creates an increase vaccum below, so the vaccum forces fuel from the idle and main metering systems. The choke housing controls the amount of vaccum (by controling the choke plate position) and therefore the amount of A/ F ratio (to an extend). So the fast idle screw has to be "balanced" with the choke housing adjustment to really set the best fast idle speed. I did check for specific fast idle speeds, and those can be found in the appropiate manufacturers manual for the specific year/model of vehicle. Maybe that is why I have not found in any of my carburator books the suggested speed except that it should be sufficient to surpass cold cracking forces exerted by oil viscosity and the like.
The darn thing is required, for the vaccum levels produced by your average 50 - 70 rpm cranking speed is not sufficient to get the idle and main metering systems to operate. However, all this effort is rooted in the lack of appropiate fuel atomization when the engine is cold. EFI has one up on carburation on this issue alone. You can start an EFI engine and get going in seconds if needed.
mvftw
Well-known member
What is your idle at?...'78's call for 1600
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- #7
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nj7000
Guest
Idle Speed
It starts out at about 1400, but then it creeps upwards towards 2000-2100 or so.
It starts out at about 1400, but then it creeps upwards towards 2000-2100 or so.
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