MY 84 GSL-SE idles at about 1800, but sometimes the engine will rev up to about 3000(while in nuetral), and then it will go back down to 1800 and rev repetively from 1800 to 2000. * the engine does this on its own. has this happened to anyone...? if so, what is wrong?

 

My SE does the same thing. Only difference is that my car does it at a higher rpm range. Here is my thread, it should be able to help you trouble shoot the problem:

https://www.rx7club.com/1st-generation-specific-1979-1985-18/85-se-strange-reving-issue-480731/

I have not had the time to fix it yet, hopefully next week some time. My '85 was doing it real bad today in stop and go traffic, it sucked.

Mike

 

is your TPS out of adjustment/bad? This happened to my bro's car (not a 7, an '89 Merkur Scorpio), he replaced the TPS and it went away.

 

TPS is a likely suspect.

David Lane's website on the GSL-SE is gone, but fortunately "bizarro" has posted David's complete article on idling problems:

https://www.rx7club.com/1st-generation-specific-1979-1985-18/gsl-se-idle-faq-link-gone-424918/