73.5T rising idle speed?

[cak]

My 73.5T's hot idle has been high lately - it gets set to 1000rpm at oil changes and it
has typically just stayed there. Now it's settling at 1400-1600. (Still has CIS.)

The throttle linkage seems to be returning fully. The throttle lever is down. I'm wondering if maybe something is causing the cold start to continue to add extra fuel?

I haven't dug very deeply. Since it's an unexpected change, I wanted to diagnose before I simply adjust...

[LakeCleElum]

Might check for a vac. leak?

My 73.5 idle speed increase about 400 rpm after a valve adjust. I think I had let it go too long as I has a few pretty tight. Once adjusted correctly, the idle speed increased.....

[ossiblue]

+1 on vacuum leak if all other simple explanations are covered. You checked the throttle position so that is not the cause. Be sure the distributor advance is also not hanging up. A small vacuum leak could easily account for what you describe. If you're cold start valve was not shutting down (it only injects when the starter is cranked) you'd have heavy carbon deposits on your plugs and tail pipe. Have you noticed that?

Do a thorough check of all hoses, fittings, and gaskets where air could enter and don't forget the front of the engine (close to the firewall and impossible to see without a mirror) as there are hoses there than can leak. Best to eliminate possible leaks before adjusting mixture, as you've already surmised.