engine and drivetrain Car suddenly idles at 2k RPM when warmed up.

[jrhone]

Its a weber 38 carb weigh electric choke. The choke to me has never been "right" just ok. Worked ok when new then never really worked properly. Was set and reset and reset by different people and it still wasn't perfect no biggie. I'm in socal and it 75 degrees 10 months out of the year. It started after long drives like an hour or more that it would idle at about 2k. Sometimes revving it would reset it back to about 1000. Now it just idles at 2k once warmed up. I thought maybe the air filter was clogged. Not enough air getting in a making it very rich and jumping the idle up so I cleaned it thoroughly. The car ran better but still the idle problem. Ideas?

[Mike Self]

Have you checked the fast idle cam?

 

A choke, regardless of whether it's manual, water or electric actually has two functions:  first it decreases the airflow to the engine, thus enriching the mixture for a cold engine to run better.  Second, it increases the idle speed so the engine won't stall while it's cold.  To perform this function, there's a mechanism attached to the choke machinery, generally called the fast idle cam. It has has rachet teeth that engage a pawl that's part of the accelerator linkage.  

 

When the engine is cold and the choke is fully "on", the rachet engages at its highest (or lowest, depending on which way you look at if) point, thus preventing the accelerator linkage from returning to its normal idle speed.  As the engine warms up and the choke graduallly turns itself off (or you do that if it's a manual), the rachet teeth engage at progressively lower points, thus decreasing the idle 'till it's back to its normal 750-800 rpm.  

 

Sounds like your fast idle cam isn't disengaging properly, and if that's happening, perhaps the choke itself isn't turning completely off.  A warm engine doesn't like an overly rich mixture and will stall.  Check all that mechanism out an report whatcha find.  It may just need some lubrication, or a little cotter pin has fallen out or the electric choke itself isn't heating properly and thus not turning the choke off  (why I like a manual choke!).

 

Happy tinkering

 

mike

Edited January 11, 2015 by mike

[jrhone]

Ok. An update. It was idling fast. Popped the air cleaner off while it was running. Pressed the butterfly and it was "stuck". Pushed it and I heard a click. I blipped the throttle and it settled to the perfect idle. So something is sticking. I'll look more carefully at the idle cam and linkage.

Edited January 11, 2015 by jrhone

[ndog]

lube the linkage my old setup did that same thing.good luck

[jrhone]

Solved, maybe.  Liberal amount of lube sprayed into the carb linkage and inside the choke assembly.  Choke hasn't stuck all afternoon.  Actually when I was at a stoplight and the choke was engaged, about 1500 RPM.  Car was warming up and I watched the RPM slowly fall to 800 RPM as the car warmed up.  That hasn't happened in a LONG time.  Usually its On or Off.  So maybe this will allow the choke to operate more reliably.