I have a problem that has me scratching my head. My "summer fun car" a 1991 firebird with the V6 MFI engine has this problem that seems to have developed from sitting over the winter.



It drives fine, but when I let my foot off the gas (no brakes applied) and it gets to about 500rpm it will surge to 1,000. I can literally coast along doing a steady 10mph without my foot on the gas while it continues to do this.



It will also do it when Im slowing down to come to a stop. BUT when I am fully stopped, it will idle just fine right at around 600-750rpm where it normally does. I can sit with my foot on the brake and nothing strange at all. Just a little normal jitter of a few rpms.



If I start it up and idle, same thing - no surge, good idle.



Any ideas on where to start looking for this bugger or what it might be?