91 LX, I have a problem with the idle racing when in park. I brought it into a local shop (chain) and they were pretty good to me though they didn't fix it - BECAUSE...

They diagnosed it 100% as an issue with the Intake Freeze Plug. Said that it pops like a fuse when their is too much expansion (e.g. water in gas). So, they wanted to replace it, but according to them it's hard getting the replacement.

According to them, the thread size is 10.2, but when they find one - and they did find one - it was sized 10.0, too small. They are blaming within-year change, so the part number (I think W0133-2369000) equals the smaller 10.0 size, not 10.2.

To their credit, they diagnosed all that for me for free, I wanted my car back after 30 days, and I said I'd look for the part myself and when I found it, I'd bring it in and they replace it.

So, just for practice, and to start, I tried today and shopping for this online doesn't seem very easy, as the name of the part changes and I rarely if ever see the 10.0/10.2 sizing mention.

I'm hesitant to go back to them at this point without having more expert knowledge on this.

So my questions are:

1) Any commentary on how valid this diagnosis is?
2) How can I confirm that this regular part was changed in 1991 and if there are different P/N?
3) What are different names for this part, so I can ID them when I search?