Cliff's Quadrajet Parts and Rebuild Kits

Quadrajet Problem Solving => Diagnose a Quadrajet carburetor problem => Topic started by: fussfeld on September 27, 2015, 08:49:00 AM

Title: Won't idle below 900rpm:
Post by: fussfeld on September 27, 2015, 08:49:00 AM

The engine will start easy and idle ALL DAY at 1300-1200rpm, choke on hi/mid step.  However at around 900-800-700 ish, choke fully open, it will stall out unless i give it gas and bring the rpm back up to 1200.

Specs:
4.3 chevy
carb is not computer controlled.

i've advanced the timing a little, but no effect so i don't think that is the problem.

i think the choke is working fine;  i had to switch to electric from hot-air.  The carb that came with this engine had the hot-air style choke even though i'm pretty sure all carbed 4.3's had electric chokes.   So it makes me wonder why the previous owner did this or his mechanic?

Title: Re: Won't idle below 900rpm:
Post by: Frank400 on September 27, 2015, 05:16:34 PM

To get any help, you'll have to provide the carb number, what was done to the carb, what it's installed in/engine specs, etc etc. 

Title: Re: Won't idle below 900rpm:
Post by: fussfeld on October 01, 2015, 06:12:12 AM

i can get the carb # in a sec.

But as an update:
i plugged the pcv line going to the carb---because i heard this is a common problem, backed timing off a little and turned the idle mix screws in one turn (they were originally 4 turns out because i thought i might be lean).

Now, after the engine gets warmed up---like 180 to 190 degrees i can get it to idle in gear no problems---all the way down to 600rpm.

Title: Re: Won't idle below 900rpm:
Post by: Cliff Ruggles on October 16, 2015, 05:14:33 AM

You are only masking the problem, or the PCV valve is defective.  Your engine needs PCV to keep the oil clean, and the atmosphere will like it better as well....Cliff