Firm84

I’ve been battling a high idle intermittently all summer with my bone stock LG4 with the factory Canadian non-computer controlled Rochester Quadrajet. The car cold starts great, idles high for a minute or two as it should, then I’ll kick it down and it’ll idle on the secondary idle position. I’ll start driving, and it drives well no hesitation or bogging, but as the car warms up the idle increases up to about 1400rpm (in neutral). Even once the car has been driven for quite a while the idle will remain high.

When I pop the hood and investigate I will find the choke partially on, still sitting on the secondary idle position. I can push the little choke lever down, and the car will idle down where it should, but as soon as I release it the little lever pops back up and puts the choke back on.

I took a couple videos and posted them here, hopefully they’re more illustrative than my description…In one video the car is running, and the other it’s off. In both videos I am pushing down on the choke lever, and you can see it just springing back on.


I can’t for the life of me understand what’s going on here? Are the linkages binding or something (I’ve sprayed them with carb cleaner a few times) somewhere? Or is the electronic choke element bad? Or something entirely different? It’s bugging me a lot since this car runs flawless otherwise….

jcat

first I do not use any carb cleaner any more. reason is it destroys the rubber/plastic and wiring insulation ..use a MAF cleaner or electronic cleaner.

with your video looks like the choke stove is open, pull off the power plug use ohmmeter the ohms should be around 20-25 ohms.. then measure the volts to it .. should be 11-12 volts engine on ..the choke does get internally damaged and then creates an open circuit so no heat is created to move the plate open ..

use electronic/maf cleaner to clean those links on the vacuum operated parts may need a small wire brush if some rust there.

Firm84

Ok, thanks, that's very helpful. Silly question, is the 'choke stove' the big round thing with the electrical connector going to it?

jcat

yes that is the heater choke.. electrical power creates the heat so the internal spring when it gets hot causes the choke lever to open the primary plate.
the spring is bimetal so that is how the spring changes shape to get this to work.. no power it is not gonna work or if the connector has no resistance then no power will heat the spring. the rivets have to be removed if the choke has NO resistance like 20-25 ohms.. no volts on connector engine on check the CH fuse under the left side of dash. 20amp CH fuse

Firm84

Alright, finally got a chance to play with this a bit. The electrical connect is good, has full voltage (12V+) when engine is running. The choke heater might be my problem since I was getting wonky ohm measurements....cold is was measuring between 16-18 ohms, once the car had warmed up I unplugged it again and it was measuring around 4 ohms then.
When I drove the car today, it did take way too long to come off of the secondary idle, but it did eventually come up and the choke opened fully....after maybe 30 minutes of run time.

NoEmissions84TA

iTrader: (1)

http://www.carburetion.com/Products/...Part=EC-8182Cx

https://cliffshighperformance.com/Qu...tail-connector

Firm84

OK, did a bit more testing today after watching some videos on how to correctly use my multimeter to measure resistance (probably should've done that first....). Now, using the meter correctly, and testing from the tab where the electrical connect would plug in, to where the choke assembly body near where it mounts to the carb I am getting a steady 14 ohms of resistance. Does that indicate a good or bad choke heater? The choke heater is like $85 locally, and with shipping to me in Canada is similar if I buy online, so I am trying to avoid throwing unnecessary parts at it.

I also noticed today that at no point in the drive cycle (including a stone-cold start) did the choke light on the dash come on....I know I've seen it lit before, but not regularly, and definitely not today. What does that indicate?

Firm84

Replaced the choke thermostat today and the problem appears to be solved, drove the car a few times running errands and the choke has been working perfectly. Once I drilled out the rivets and installed the new heater/thermostat I reset the adjustments using this tech article from the Corvetteforum, very good reference if anyone ever needs it:
https://www.corvetteforum.com/forums...jet-choke.html

jcat

good you did work it out as I stated , so the fix was not a big issue ...
these choke heaters do get damaged because of the high temps and the design .. over time this is a regular replace item ... if you have converters good to check it every oil change . decades ago I was not liking how GM riveted these in place . I fabricated the choke key so in summer less choke winter a bit more choke..