I have read several post trying to figure out my extremely high idle, and I am confused about the choke circuit. My understanding is that the choke is operated on a temperture basis. If that is so, why is their always 12 volts present when the car is started? Why have a relay? What is the source of heat that is suppose to make the bimetal react? Is it strictly current from alt(gen). I'm lost. I know choke is bad but I want to understand before I just replace it. Thanks for your help.

86 z28 305 H/ rochester quadjet(elctric choke)
Car is idling over 2000 rpms/i can go 35 mph without touching gas.



Rob

 

Originally, the 'automatic' choke was designed(years ago) to open via heat from the engine--before that is was cable operated from inside the car. On later carbs, like yours, electricity is used to heat-up the choke faster than the engine would otherwise heat it up--Called the eletric choke. So yes it needs 12v when the engine is running. Or, 12v when the key is in the run position. Are you sure your's doesn't just need adjusted and/or cleaned up? 2000 rpm idling is too fast even with the choke on--fast idle should not be that high. Ask the board 'how to adjust the fast idle speed on a q-jet'--it's not something I've had to do. I could tell you if it was a holley

 

A Rochester E4ME (or E2SE, for that matter) has a resistive heating element in the choke coil cover. Measure teh resistance of the heating element from teh power connection to a good ground. You should be able to read in the range of 35-50 ohms. Anything above 1,000 ohms indicates a problem with the element or grounding through the carb body and intake.

 

Thanks for the info. When I get home I will ohm out the choke.

I have one more question. What is the value of the coil for the relay suppose to be? Just curious.

Thanks

Rob

 

35-65 ohms is good. 50 is a perfectly new one.

 

Odd. Just checked several known good ones and I got ~4 Ohms across all of them, including a brand new one.

Since the choke element is actually used as a ground in some circuits (the choke/oil light, notably) this makes sense if you think about it.

I used an analog Ohmmeter and zero'ed out the scale perfectly before taking a reading. I have seen weird readings across the choke when using a digital Ohmmeter. I have no explanation for this, just stating my actual observations.

 

Question:
Do you have 12 volts at the choke?