Very High Idle

[RussMcB]

I enjoyed having a nice low idle for a couple of minutes, but it was back high again by the first stop light.

When I got back home I did the phone book trick to stop the air going into the front snout and my idle stayed high. So, sure enough, I do have a large vacuum leak problem.

With the car running and the snout still blocked, I pulled and plugged all the easy-to-reach vacuum hoses one at a time. I could hear slight changes in RPM but none of them brought the idle down when it should be. I think that means my large leak may be under the plenum.

Today I'll repeat those tests, and try a few more things with the plenum in place, then pull it if I haven't found the leak yet.

I'm wondering if, since the idle was nice and low for a few minutes, maybe the leak is related to a source that is being controlled by the car.

Saturday afternoon update:
I blocked off the front snout, ran the car at idle, sprayed some carb cleaner under the plenum (front area) and the idle went up. So, I'm taking off the plenum now, expecting/hoping to find an obvious problem.