The 1947 - Present Chevrolet & GMC Truck Message Board Network - View Single Post - New Q-Jet will not settle down to idle, it's driving me %$#%$#%$

Rollo Grande · 07-25-2020, 06:16 PM

1970 C/20 350 4v

My old carb backfired, spit flames, and sucked in every way...but it idled just fine.

Bought a brand new Quadrajet from a carb warehouse and it solved all of the big problems, but it will consistently not come down off high idle. I have to drive around blipping the throttle constantly to get it to calm down. It hangs up at 2500rpm, 1500, 1200, 1900, wherever.

I just tuned both screws using a vacuum gauge to 19 inches and set the idle speed around 800. Nothing changed.

Also this new carb is giving me 5mpg city, just like the old one did.

I suspect it might be missing a piece, that rich/lean clockspring thing, but they sold it to me as a complete plug and play "divorced choke" or whatever. I don't know that much about these things.

Any idea what to do?

07-25-2020, 06:16 PM	#1
Rollo Grande Registered User Join Date: Nov 2019 Location: San Francisco Posts: 8	New Q-Jet will not settle down to idle, it's driving me %$#%$#%$ 1970 C/20 350 4v My old carb backfired, spit flames, and sucked in every way...but it idled just fine. Bought a brand new Quadrajet from a carb warehouse and it solved all of the big problems, but it will consistently not come down off high idle. I have to drive around blipping the throttle constantly to get it to calm down. It hangs up at 2500rpm, 1500, 1200, 1900, wherever. I just tuned both screws using a vacuum gauge to 19 inches and set the idle speed around 800. Nothing changed. Also this new carb is giving me 5mpg city, just like the old one did. I suspect it might be missing a piece, that rich/lean clockspring thing, but they sold it to me as a complete plug and play "divorced choke" or whatever. I don't know that much about these things. Any idea what to do?