My '77 has this exact same problem. It backfires while
idling down from high RPMs. I removed the air pump
belt to eliminate the back firing, but don't like the
idea of removing emission devices. Plus, my air pumps
works good I don't want it to freeze up.
I thought maybe the check-valve on the tube behind the
air pump was shot.... allowing the back-fire.
How could the catalytic converter be the cause of the
problem? Restricted flow?
--- Atwell Haines <firstname.lastname@example.org> wrote:
> At 07:52 PM 6/13/99 -0400, Sam Gentry wrote:
> >We just got the 80 spit running and it works well
> EXCEPT: When we rev the
> >engine and let it coast down it backfires and gets
> very rich. Works great
> >if we eliminate the air pump. Any ideas? I would
> like to keep the
> >emission stock if possible.
> Chances are that your catalytic converter is shot.
> That's an expensive
> repair. :(
> I have left the air pump disconnected on mine
> because of that. Plus, my
> air pump is a bit noisy also. (Another expensive
> repair) It passed the NJ
> idle emissions test that way... :)
> Also, there is an off chance that your
> bypass/deceleration valve (front
> side of carb) has been blanked off.
> Atwell Haines
> '79 Spitfire
> Succasunna, NJ USA
> "If horrific means to make horrible, doesn't
> terrific mean to make