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Old 02-13-2018, 06:59 PM   #1
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Join Date: Jan 2014
Location: Ft Myers Florida
Posts: 571
Sudden idle problem

Truck idled perfectly up until last night, I did a compression test of the cylinders and right after that it started idling like piss. 70's era 305 (not 350) , quadrajet 4 barrel carb. HEI. All plug wires are connected where they should be. Plugs themselves are new less than 20 miles on them.

I started my trouble shooting by messing with the idle mixture screws and I discovered that I can now turn them both all the way in without any ill effects other than slight increase in rpms. Is this always an issue with the carb? Just the other day the engine would stall if I turned them in.

I don't have a tach but I definitely feel the rpms are higher than normal idle would be, this is NOT being caused by throttle linkage or idle speed set screw. I'm not sure if something such a vacuum leak could increase the rpm's resulting in getting no response in the idle circuit or whatnot, could it?

Either I disturbed something that caused this or the carb just happened to act up in between starts. No vacuum leaks found as of yet anyway.

EDIT: To be clear, I didn't do the compression test due to the poor idle. It was unrelated and afterwards is when the poor idle came about.
1968 C10
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