weather turned cold and idle goes up

[kreb]

my idle gets a little high when the temp goes to 50* or lower. this is after warm up. should the choke be set to leaner or richer for colder temps? could the high idle be caused by a vacuum leak, if so any idea from where? thanks

benjamin

[derf]

With a properly functioning choke, your idle should go up after you start it but should kick down to normal once you get the engine running.

The choke doesn't directly affect the mixture. It simply puts a restrictor plate over the top of the venturis to restrict airflow when the engine is cold. It also engages the fast idle cam to keep the RPMs up while warming up the engine. As it opens up, the fast idle cam moves out of the way and the RPMs should drop when you give the accelerator a quick kick.

Check to make sure that the plate on the top of the carb slowly opens up on its own after you start the cold engine. If it doesn't, you need to make sure the choke heater (electric or exhaust) is working properly. If it's not, you need to check for 12 volts at the red wire that connects to the choke or check the hoses that go from the manifold to the choke. If you don't have either, you need one or the other. An electric connection is the easiest to retrofit.