[Jdub]

Plain:

It's a US, non-California, 49-stater. And yes, it ONLY happens after running on the hiway for a bit of time. Car is warm, and the idle just won't turn down; sits about 1800rpm.

My approach solved the problem, period. I am told that you must have *some* decel to prevent the backfire as described above. And note that the locknut is on very, very tight. I thought I would bust the unit before it freed up finally.

This should be done in concert with removing the rubber boot...makes life much simpler, access-wise, and also lets you clean the throttle plate (i.e. butterfly) and the sensor plate from the topside. I think you will find yours is probably dirty, especially if you ever overfilled the oil!

Good luck,
Jw