High idle when cold

[Cookie]

Hello MSC, new guy here

I just picked up a pretty clean K10, it runs beautifully with the exception of a high idle speed when cold. After a couple of minutes (literally 2 or 3 mins) it settles down. My bet would be that the auto choke needs setting but I thought I'd see what you guys thought before I started fiddling. Has anyone else experienced this or have any other thoughts?

 

[skymera]

How high?

Sounds normal to me. My K11 idled higher for a few miles before dropping to around 750rpm

 

[Cookie]

Well, I don't have one of those fancy rev gauges, but I'd guess *around* 2K RPM, I can pull away without using the accelerator.

 

[davidb]

This is usually a problem with the autochoke - I'm guessing these have an electrically heated bimetal thingy.
In the olden days, the choke used to be operated by coolant, and as it warmed up, the choke throttle plate opened up. 'Recently' (ie about 30 years ago), they replaced this with a coil on the side of the choke - a heating element sits on it, and as it heats up, the coil which has two different metals on each side changes shape and opens the throttle plate. When the choke is closed, it is pulling in more fuel and less air - fuel vapourises less easily in a cold engine. So this method adds more fuel to the mixture. As it warms up, the choke opens and the mixture returns to a more even fuel/air ratio.

Usually a cure is the slam the throttle pedal down before you start the car - this 'resets' the choke throttle plate, and you may have different rpm when you start.
This is the choke on my Subaru Justy:

The autochoke mechanism is on the side (the round black thing). The throttle plate is at the back - on K10's, the carb is rotated 90 degrees.
Try not to mess with the fuel mixture and idle setting - if these are factory set, they are usually spot on and can be difficult to set right once they are altered.

I have a spare carb for these if you want it for a 10'er.

 

[Cookie]

Cheers, I'm pretty certain it's an auto-choke issue now so I'll have a fiddle with it when I get a moment. It looks similar to the Justy carb - a little 'tub' on the back with a bi-metallic spring and a cam inside. I'll grab a Haynes/workshop manual and see about setting it up. The fuel mix and idle are fine so I'll leave them well alone!

 

[frank]

there should be a fast idle adjusting screw under the carb, and an idle-up valve/solenoid on the later eccs k10,s iirc

 

[Cookie]

Sweet, I'll check that out too - thanks for the info dude

 

[davidb]

I think the fast idle screw is only on US (or europe I can't remember) Micras.