73-87 Chevy _ GMC Trucks > Fuel Systems and Drivability
Idle specs for 1978 Rochester quadrajet
MY1978:
Can someone please provide me with the idle specs for a Rochester 4bbl quadrajet. When i start it when cold it wants to stall out several times unless I push the accelator pedal to rev back up. After it starts warming up it will ramp up to high idle and then after the given warm up time (which seems like forever based on today's vehicles) it will idle down to mid and then low with a kick down.
So, can someone tell me what the idle speed(s) should be please. I have someone that is coming over today to work on it.
Thanks
zieg85:
There is a lot of information on the web if you google it. From your description it sounds to me like your choke pull-off isn't adjusted right.
Mr Diesel:
#1. Don't ever compare a 1970s or 1980s carbureted vehicle to a modern vehicle. There is no comparison and they will never be comparable. These old vehicles usually warm up a lot slower than a modern vehicle at idle. The fastest way to warm up an engine is to drive it.
#2. Set the idle speeds at whatever suits you and the driveability. Generally I like my warm idle set around 700rpm and cold high idle 1,000-1,200. It doesn't matter what any manual or spec sheet says is "right" for it.
JohnnyPopper:
I read thru the thread a couple of times, did someone make a comparison? ;D
Unless you have a manual choke (if you dont have a cable to pull, it's not manual) your carb operates with a single pump before starting. Not a light pump, push at least half way.
If your engine/carb is cold, a properly adjusted choke will engage to the degree needed. After the warmup, the the kick down you speak of will bring down to the low idle.
Check out this info. https://www.youtube.com/watch?v=_BTEdWt2V3s&t=103s
Which one are you?
zieg85:
--- Quote from: JohnnyPopper on August 20, 2023, 04:26:57 PM ---I read thru the thread a couple of times, did someone make a comparison? ;D
Unless you have a manual choke (if you dont have a cable to pull, it's not manual) your carb operates with a single pump before starting. Not a light pump, push at least half way.
If your engine/carb is cold, a properly adjusted choke will engage to the degree needed. After the warmup, the the kick down you speak of will bring down to the low idle.
Check out this info. https://www.youtube.com/watch?v=_BTEdWt2V3s&t=103s
Which one are you?
--- End quote ---
This is what is out of adjustment and what is called a choke pull-off
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